{"title":"KR Audio","description":null,"products":[{"product_id":"300b-tube-pair","title":"300B Vacuum Tube","description":"\u003cbuilder-component rev=\"kvfbed4enmq\" api-key=\"48d1cdcd52ec4d289f1ef8c4f75da167\" options='{\"locale\":\"Default\"}' name=\"product-description\" entry=\"5700c7c03bc24481b6522bf136a9fc49\"\u003e\n\n\u003c!-- ***** Generated by Builder.io on Mon, 08 Jun 2026 19:49:08 GMT ***** --\u003e\n\n\u003cstyle type=\"text\/css\" class=\"builder-styles builder-api-styles\"\u003e\/*start:h47494*\/.css-h47494{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;-webkit-align-items:stretch;-webkit-box-align:stretch;-ms-flex-align:stretch;align-items:stretch;}\/*end:h47494*\/ 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class=\"builder-content\" builder-content-id=\"5700c7c03bc24481b6522bf136a9fc49\" builder-model=\"product-description\"\u003e\u003cdiv data-builder-component=\"product-description\" data-builder-content-id=\"5700c7c03bc24481b6522bf136a9fc49\" data-builder-variation-id=\"5700c7c03bc24481b6522bf136a9fc49\"\u003e\n\u003cstyle data-emotion-css=\"h47494\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-blocks css-h47494\" builder-type=\"blocks\"\u003e\n\u003cstyle data-emotion-css=\"rm3vjx\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-3c0dc031bfaf495eae54fa76e67a7108 builder-has-component css-rm3vjx\" builder-id=\"builder-3c0dc031bfaf495eae54fa76e67a7108\"\u003e\n\u003cstyle data-emotion-css=\"1840m1q\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-columns css-1840m1q\"\u003e\n\u003cstyle data-emotion-css=\"1ukkadj\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-column css-1ukkadj\"\u003e\u003cdiv class=\"builder-blocks builder-blocks-child css-h47494\" builder-type=\"blocks\" builder-parent-id=\"builder-3c0dc031bfaf495eae54fa76e67a7108\"\u003e\n\u003cstyle data-emotion-css=\"qcdo0v\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-9d1426c799354b3bbed7e177e9ec0bc5 builder-has-component css-qcdo0v\" builder-id=\"builder-9d1426c799354b3bbed7e177e9ec0bc5\"\u003e\n\u003cstyle data-emotion-css=\"1qggkls\"\u003e\u003c\/style\u003e\n\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eIntroducing the New for 2024, the revised KR Audio 300B Tube. A true powerhouse in the world of high-end audio. These low-frequency, high-power triodes are designed to deliver an unparalleled listening experience, offering 6-12 watts of pure class-A power per tube. Whether you're a seasoned audiophile or a passionate music lover, the KR Audio 300B Tube is sure to elevate your audio setup to new heights. The new version has a Higher Transconductance. In a vacuum tube, transconductance is a measure of the tube's gain or how much it amplifies a signal at a given bias setting. Thus, you have more gain to play with. The Tube Bias is much more stable, which means a longer life.\u003c\/p\u003e\n\u003cp\u003eFully compatible with classic 300B designs, these tubes are meticulously crafted to provide a seamless upgrade for your existing amplifier. The KR Audio 300B Tube maintains the cherished sonic characteristics of vintage 300B tubes while incorporating modern manufacturing techniques and premium materials to ensure exceptional reliability and consistency. When it comes to performance, the KR Audio 300B Tube is in a league of its own. These triodes effortlessly deliver a warm, rich, and highly detailed sound, with a wide and deep soundstage that immerses you in your favorite recordings. The 300B's ability to reproduce music with unrivaled clarity, dynamics, and emotional impact is why it has remained a favorite among audio enthusiasts for decades.\u003c\/p\u003e\n\u003cp\u003eThe KR Audio 300B Tube's impressive power output of 6-12 watts per tube in pure class-A operation ensures that your amplifier has the headroom necessary to handle even the most demanding musical passages with ease. This robust power delivery, combined with the 300B's inherent linearity and low distortion, results in a listening experience that is both engaging and fatigue-free. KR Audio's commitment to quality is evident in every aspect of these tubes' construction. From the carefully selected materials to the rigorous testing and matching process, no detail has been overlooked in the pursuit of audio perfection. Each tube in the matched pair is built to exacting standards, ensuring optimal performance and longevity.\u003c\/p\u003e\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"ur9nhf\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-f812277152e846bc890a76550e69033c css-ur9nhf\" builder-id=\"builder-f812277152e846bc890a76550e69033c\"\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"hgfgng\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-d44339f5072a4c69ba3cc45f3ae9c70e builder-has-component css-hgfgng\" builder-id=\"builder-d44339f5072a4c69ba3cc45f3ae9c70e\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eAbout the 300B Tube: The Legendary Power Triode\u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-e20f6c94e3b5431692398e512a8de57b builder-has-component css-hgfgng\" builder-id=\"builder-e20f6c94e3b5431692398e512a8de57b\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eThe 300B tube, originally designed by Western Electric (WE 300B\/Western Electric 300B) in the 1930s, has become a legendary electron tube in the world of hi-fi audio. Known for its exceptional midrange and high-frequencies performance, warm tonal qualities, and ability to deliver a highly musical and engaging listening experience, the 300B has been a favorite among audiophiles and music enthusiasts for decades. As a directly heated power triode, the 300B features a cathode that also serves as the filament, contributing to its unique sonic characteristics. This design allows for a simplified and more efficient electron emission process, resulting in a purer and more lifelike sound quality.\u003c\/p\u003e\n\u003cp\u003eThe 300B's anode, coupled with its high amplification factor and low plate resistance, enables it to deliver a robust and dynamic performance in both single-ended and push-pull amplifier configurations. This versatility has made the 300B a popular choice for a wide range of applications, including power amplifiers, tube amps, integrated amplifiers, and preamplifiers (preamp). While Western Electric's production of the 300B ceased in the 1980s, several manufacturers, such as KR Audio, Electro-Harmonix, and JJ Electronic, have continued to produce high-quality 300B tubes. These new production tubes, like the JJ 300B, aim to capture the essence of the original WE 300B while incorporating modern manufacturing techniques and materials to ensure reliability and consistency. We believe that the KR Audio 300B is the superior version of the 300B tube today.\u003c\/p\u003e\n\u003cp\u003eWhen paired with high-quality transformers and well-designed circuitry, the 300B tube can create an immersive and emotionally engaging listening experience. Its ability to reproduce music with a sense of warmth, smoothness, and natural detail has earned it a reputation as one of the best-sounding power tubes available.\u003c\/p\u003e\n\u003cp\u003eAudiophiles and music lovers in the USA and around the world continue to seek out 300B-based tube amplifiers and preamplifiers for their ability to deliver a truly captivating hi-fi experience. Many manufacturers offer amplifiers designed around the 300B, ranging from single-ended triode (SET) designs to more powerful push-pull configurations.\u003c\/p\u003e\n\u003cp\u003eWhether you're building a new tube amplifier or upgrading an existing one, the 300B tube is an excellent choice for those seeking the ultimate in musical performance, emotional engagement, and the best sound quality. With its rich history, legendary status, and unrivaled sonic qualities, the 300B continues to be a cornerstone of high-end audio.\u003c\/p\u003e\n\u003cp\u003eEnter KR Audio. \u003c\/p\u003e\n\u003cp\u003eKR Audio is one of the world’s top manufacturers of vacuum tubes and high-end vacuum tube amplifiers, all crafted with care right in the beautiful Czech Republic. KR Audio specializes in producing low-frequency power triodes and high-end audio equipment, all made by hand! From selecting the glass to their meticulous artisan work in metal and glass blowing, every step is done with the utmost attention to detail. Their commitment to quality means they never use automated lines—this is what sets KR Audio apart and ensures our products are truly exceptional.\u003c\/p\u003e\n\u003cp\u003eA bit about KR Audio history: KR Audio's journey started in the late 1950s when a young Riccardo Kron, while assisting his professor, became curious about why even the best tubes tended to drift over time. This sparked a lifelong quest to enhance tube performance, a passion he carried through his time at Deutsche Grammophon and Magnadyne. Following the fall of communism, Riccardo teamed up with a talented research and development group from TESLA LABORATORIES in the Czech Republic. Together, they pioneered the creation of hand-crafted vacuum tubes designed specifically for audio, utilizing improved materials, higher vacuum levels, and rigorous quality control. The result? Tubes that deliver incredible dynamics, finer resolution, and an almost tangible sound experience.\u003c\/p\u003e\n\u003cp\u003eKR AUDIO Electronic SRO began as a tube manufacturer and has since evolved into a developer of world-class amplifiers, employing a unique reverse hybrid system to enhance your listening experience. Thank you for considering KR Audio—we're excited to share KR Audio's passion for high-quality sound with you!\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-e00c3ce7316e4bab84e8bf121d7c8401 css-ur9nhf\" builder-id=\"builder-e00c3ce7316e4bab84e8bf121d7c8401\"\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"15auezb\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-0db86629d5504683a2ab9a8d4e9ea0fb builder-has-component css-15auezb\" builder-id=\"builder-0db86629d5504683a2ab9a8d4e9ea0fb\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eKR Audio WARRANTY ON TUBES ONLY \u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"138u8cp\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-f480e8cd60e54e42b81501286a5fdfd0 builder-has-component css-138u8cp\" builder-id=\"builder-f480e8cd60e54e42b81501286a5fdfd0\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003ePlease take a moment to return your warranty registration form included with the tubes. Unregistered KR tubes will not be warranted. Customers must return the warranty registration when the tubes have been received. \u003c\/p\u003e\n\u003cp\u003eKR Audio Electronics will respect valid warranty claims. Incorrect claims or late warranty registration will void any guarantee. KR Audio Electronics will replace the tube provided the following conditions are met: 1) The tubes were used according to the technical data sheet enclosed with the KR tube. 2) Abuse, accident or unauthorized use of the tube will be determined by KR Audio Electronics. 3) All tubes to be returned with the original factory box and warranty. 4) To obtain a replacement for a faulty tube, KR Audio Electronics reserves the right to obtain dealer or distributor authorization prior to shipping products pre-paid back to us. \u003c\/p\u003e\n\u003cp\u003eKR Audio Electronics gives a one-year warranty for your tube from the date of purchase. The purchase date should be written or stamped by the dealer or distributor on the day you buy the tube. Only expert technicians can change the work point of the tube. Improper use of the tube or incorrect application of the tube to a circuit cannot be covered by our warranty.  \u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"p548tv\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-84ccdf250e6b4ace92abeafe16f31e13 builder-has-component css-p548tv\" builder-id=\"builder-84ccdf250e6b4ace92abeafe16f31e13\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eMoon Audio Tube Testing Process\u003c\/h3\u003e\n\u003cp\u003eOur high-end audio systems achieve sonic purity through the use of carefully selected NOS vacuum tubes. We take time to search for NOS tubes, understanding their unique potential for audio reproduction. Each tube is rigorously tested using legendary HICKOK 800K 600K Dynamic Mutual Conductance Tube Tester and TV7-A\/U Vacuum Tube Testers to measure critical parameters, including mutual conductance, emission, and gas levels. By precisely matching tubes based on these measurements, we deliver balanced, dynamic, and lifelike audio that elevates your listening experience to an art form.  \u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-cc3b7e94f33e47af822f1bd437601682 css-ur9nhf\" builder-id=\"builder-cc3b7e94f33e47af822f1bd437601682\"\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-6aafcb3e6e1048539960a56ee4aa7965 builder-has-component css-15auezb\" builder-id=\"builder-6aafcb3e6e1048539960a56ee4aa7965\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eF.A.Q\u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"1q0cqwd\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-2c78b9fecd884a0bb14d9b015339e2eb builder-has-component css-1q0cqwd\" builder-id=\"builder-2c78b9fecd884a0bb14d9b015339e2eb\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003e\u003cstrong\u003eQ: What is a 300B tube and how does it work?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA: The 300B is a directly heated triode vacuum tube used in audio amplification. It operates by passing an electric current through a heated cathode to emit electrons, which are then controlled by a grid to amplify the input signal.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: What amplifiers use the 300B tube?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA: The 300B tube is commonly found in single-ended triode (SET) amplifiers renowned for their rich, warm sound signature. Many high-end audio manufacturers like \u003ca href=\"https:\/\/www.moon-audio.pro\/brands\/kr_audio.html\" rel=\"noopener noreferrer\" target=\"_blank\"\u003eKR Audio\u003c\/a\u003e produce amplifiers utilizing the 300B tube for audiophile-grade sound reproduction.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: What are the sonic characteristics of the 300B tube?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA: The 300B tube is prized for its lush midrange, smooth treble, and natural timbre. It delivers a musical, euphonic sound signature with a captivating sense of realism and intimacy.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Can I replace the 300B tube in my amplifier with a different type?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA: While some amplifiers allow tube rolling, it's essential to consult the manufacturer's specifications and recommendations. Substituting the 300B tube with a different type may alter the \u003ca href=\"https:\/\/www.moon-audio.pro\/headphone-amplifiers-dacs\/amplifiers.html\" rel=\"noopener noreferrer\" target=\"_blank\"\u003eamplifier's\u003c\/a\u003e performance and sound characteristics.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: How long does a 300B tube typically last?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA: The lifespan of a 300B tube varies depending on usage, operating conditions, and tube quality. On average, a well-maintained 300B tube can last several thousand hours before requiring replacement.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: How do I bias a 300B tube amplifier?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA: Biasing a 300B tube amplifier involves adjusting the bias voltage to ensure proper operating conditions and optimal performance. Consult the \u003ca href=\"https:\/\/www.moon-audio.pro\/headphone-amplifiers-dacs\/amplifiers.html\" rel=\"noopener noreferrer\" target=\"_blank\"\u003eamplifier's\u003c\/a\u003e user manual or seek assistance from a qualified technician for precise biasing procedures. Feel free to \u003ca href=\"https:\/\/www.moon-audio.pro\/contact-us\" rel=\"noopener noreferrer\" target=\"_blank\"\u003eContact Us\u003c\/a\u003e and we'll be more than happy to assist you.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: What are the pros and cons of using a 300B tube amplifier?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA: Pros include exceptional sound quality, musicality, and compatibility with high-efficiency speakers. Cons may include higher cost, lower power output compared to other tube types, and the need for occasional tube replacement.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Are there different brands or versions of the 300B tube?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA: Yes, various manufacturers produce 300B tubes, each with unique construction, materials, and sonic characteristics. Popular brands include Western Electric, \u003ca href=\"https:\/\/www.moon-audio.pro\/brands\/kr_audio.html\" rel=\"noopener noreferrer\" target=\"_blank\"\u003eKR Audio\u003c\/a\u003e, TJ Full Music, Sophia Electric, and Shuguang.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: What are the differences between vintage and modern production 300B tubes?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA: Vintage 300B tubes are highly sought after for their historical significance and reputed sound quality. Modern production tubes offer advancements in manufacturing techniques and may provide improved reliability and consistency.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: How do I select the right 300B tube for my amplifier?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA: Consider factors such as brand reputation, sonic preferences, budget, and compatibility with your amplifier. Researching reviews, seeking advice from audio enthusiasts, and experimenting with different tubes can help you find the perfect match for your system. We consider the version by \u003ca href=\"https:\/\/www.moon-audio.pro\/brands\/kr_audio.html\" rel=\"noopener noreferrer\" target=\"_blank\"\u003eKR Audio\u003c\/a\u003e to be one of the best on the market.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"1n465md\"\u003e\u003c\/style\u003e\n\u003cimg src=\"https:\/\/cdn.builder.io\/api\/v1\/pixel?apiKey=48d1cdcd52ec4d289f1ef8c4f75da167\" aria-hidden=\"true\" alt=\"\" role=\"presentation\" width=\"0\" height=\"0\" class=\"builder-block builder-pixel-yd0w270jdd css-1n465md\" builder-id=\"builder-pixel-yd0w270jdd\"\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\u003c\/div\u003e\u003c\/builder-component\u003e\n\u003cscript async src=\"https:\/\/cdn.builder.io\/js\/webcomponents\"\u003e\u003c\/script\u003e","brand":"KR Audio","offers":[{"title":"Pair ($1400)","offer_id":49668508975418,"sku":"300B-KRM-1","price":1400.0,"currency_code":"USD","in_stock":true},{"title":"Quad ($2800)","offer_id":49668509008186,"sku":"300B-KRM-2","price":2800.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0834\/0245\/7402\/files\/KR_Audio_300B_Tube_Pair__79261.1715879618.1280.1280.jpg?v=1719257326"},{"product_id":"2a3-tube-pair","title":"2A3 Vacuum Tube","description":"\u003cbuilder-component rev=\"xtyqk7nfsb\" api-key=\"48d1cdcd52ec4d289f1ef8c4f75da167\" options='{\"locale\":\"Default\"}' name=\"product-description\" entry=\"388f596043fb4bbea5c53410dfaff2fe\"\u003e\n\n\u003c!-- ***** Generated by Builder.io on Fri, 18 Jul 2025 14:20:18 GMT ***** --\u003e\n\n\u003cstyle type=\"text\/css\" class=\"builder-styles builder-api-styles\"\u003e\/*start:h47494*\/.css-h47494{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;-webkit-align-items:stretch;-webkit-box-align:stretch;-ms-flex-align:stretch;align-items:stretch;}\/*end:h47494*\/ \/*start:ga7wz6*\/.css-ga7wz6.builder-block{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;position:relative;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;box-sizing:border-box;margin-top:0px;margin-left:auto;margin-right:auto;max-width:800px;}\/*end:ga7wz6*\/ \/*start:1840m1q*\/.css-1840m1q{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;}@media (max-width:999px){.css-1840m1q{-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;-webkit-align-items:stretch;-webkit-box-align:stretch;-ms-flex-align:stretch;align-items:stretch;}}\/*end:1840m1q*\/ \/*start:1ukkadj*\/.css-1ukkadj{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;-webkit-align-items:stretch;-webkit-box-align:stretch;-ms-flex-align:stretch;align-items:stretch;line-height:normal;width:calc(100% - 0px);margin-left:0;}.css-1ukkadj \u003e .builder-blocks{-webkit-box-flex:1;-webkit-flex-grow:1;-ms-flex-positive:1;flex-grow:1;}@media (max-width:999px){.css-1ukkadj{width:100%;margin-left:0;}}\/*end:1ukkadj*\/ \/*start:qcdo0v*\/.css-qcdo0v.builder-block{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;position:relative;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;box-sizing:border-box;margin-top:0px;line-height:normal;height:auto;}\/*end:qcdo0v*\/ \/*start:1qggkls*\/.css-1qggkls{outline:none;}.css-1qggkls p:first-of-type,.css-1qggkls .builder-paragraph:first-of-type{margin:0;}.css-1qggkls \u003e p,.css-1qggkls .builder-paragraph{color:inherit;line-height:inherit;-webkit-letter-spacing:inherit;-moz-letter-spacing:inherit;-ms-letter-spacing:inherit;letter-spacing:inherit;font-weight:inherit;font-size:inherit;text-align:inherit;font-family:inherit;}\/*end:1qggkls*\/ \/*start:hgfgng*\/.css-hgfgng.builder-block{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;position:relative;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;box-sizing:border-box;margin-top:20px;line-height:normal;height:auto;}\/*end:hgfgng*\/ \/*start:ur9nhf*\/.css-ur9nhf.builder-block{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;position:relative;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;box-sizing:border-box;margin-top:20px;height:2px;background-color:rgba(221,221,221,1);}\/*end:ur9nhf*\/ \/*start:1mvsfya*\/.css-1mvsfya.builder-block{height:0;width:0;display:inline-block;opacity:0;overflow:hidden;pointer-events:none;}\/*end:1mvsfya*\/\u003c\/style\u003e\n\u003cdiv class=\"builder-component builder-component-388f596043fb4bbea5c53410dfaff2fe\" data-name=\"product-description\" data-source=\"Rendered by Builder.io\"\u003e\u003cdiv class=\"builder-content\" builder-content-id=\"388f596043fb4bbea5c53410dfaff2fe\" builder-model=\"product-description\"\u003e\u003cdiv data-builder-component=\"product-description\" data-builder-content-id=\"388f596043fb4bbea5c53410dfaff2fe\" data-builder-variation-id=\"388f596043fb4bbea5c53410dfaff2fe\"\u003e\n\u003cstyle data-emotion-css=\"h47494\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-blocks css-h47494\" builder-type=\"blocks\"\u003e\n\u003cstyle data-emotion-css=\"ga7wz6\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-38356bdcea0646d69bd145a185549319 builder-has-component css-ga7wz6\" builder-id=\"builder-38356bdcea0646d69bd145a185549319\"\u003e\n\u003cstyle data-emotion-css=\"1840m1q\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-columns css-1840m1q\"\u003e\n\u003cstyle data-emotion-css=\"1ukkadj\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-column css-1ukkadj\"\u003e\u003cdiv class=\"builder-blocks builder-blocks-child css-h47494\" builder-type=\"blocks\"\u003e\n\u003cstyle data-emotion-css=\"qcdo0v\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-26e45f51c0644bf096a01259fb64c52c builder-has-component css-qcdo0v\" builder-id=\"builder-26e45f51c0644bf096a01259fb64c52c\"\u003e\n\u003cstyle data-emotion-css=\"1qggkls\"\u003e\u003c\/style\u003e\n\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eIntroducing the KR Audio 2A3 matched pair, a set of two expertly crafted tubes designed to elevate your audio experience to new heights. These low-frequency, low-power triodes deliver an impressive 2-5 Watts of pure class-A power, ensuring your music is reproduced with unparalleled clarity and warmth. This matched pair is meticulously engineered to provide the ultimate sonic experience for discerning audiophiles and music enthusiasts alike.\u003c\/p\u003e\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"hgfgng\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-d2f937ac9442480ab742051bf886ecd0 builder-has-component css-hgfgng\" builder-id=\"builder-d2f937ac9442480ab742051bf886ecd0\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eThe KR Audio 2A3 tubes are fully compatible with any well-designed 2A3 amplifier, making them the perfect upgrade for your existing setup. These tubes deliver exactly what owners of these special amplifiers expect: a pure sense of space, perfect subtle timing cues, and a brilliant tone that will transport you to the heart of your favorite recordings.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-b3de35ccf9654ed695e5831d013166c4 builder-has-component css-hgfgng\" builder-id=\"builder-b3de35ccf9654ed695e5831d013166c4\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eThe 2A3 tubes offer a level of performance that sets them apart from the competition, thanks to KR Audio's commitment to quality and attention to detail. Whether you're a seasoned audiophile or simply appreciate the finer things in life, the KR Audio 2A3 tubes are the go-to choice for anyone seeking to elevate their 2A3-based system to new heights. Experience the difference for yourself and discover why these tubes have earned a reputation as the ultimate upgrade for 2A3 enthusiasts worldwide.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-764c61f976d147b886ab39398408f126 builder-has-component css-hgfgng\" builder-id=\"builder-764c61f976d147b886ab39398408f126\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eKR Audio WARRANTY ON TUBES ONLY \u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-67d5f22a389e4904b0a94b7809d50dcc builder-has-component css-hgfgng\" builder-id=\"builder-67d5f22a389e4904b0a94b7809d50dcc\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003ePlease take a moment to return your warranty registration form included with the tubes. Unregistered KR tubes will not be warranted. Customers must return the warranty registration when the tubes have been received. \u003c\/p\u003e\n\u003cp\u003eKR Audio Electronics will respect valid warranty claims. Incorrect claims or late warranty registration will void any guarantee. KR Audio Electronics will replace the tube provided the following conditions are met: \u003c\/p\u003e\n\u003col\u003e\n\u003cli\u003eThe tubes were used according to the technical data sheet enclosed with the KR tube. \u003c\/li\u003e\n\u003cli\u003eAbuse, accident or unauthorized use of the tube will be determined by KR Audio Electronics. \u003c\/li\u003e\n\u003cli\u003eAll tubes to be returned with the original factory box and warranty. \u003c\/li\u003e\n\u003cli\u003eTo obtain a replacement for a faulty tube, KR Audio Electronics reserves the right to obtain dealer or distributor authorization prior to shipping products pre-paid back to us. \u003c\/li\u003e\n\u003c\/ol\u003e\n\u003cp\u003eKR Audio Electronics gives a one-year warranty for your tube from the date of purchase. The purchase date should be written or stamped by the dealer or distributor on the day you buy the tube. Only expert technicians can change the work point of the tube. Improper use of the tube or incorrect application of the tube to a circuit cannot be covered by our warranty. \u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"ur9nhf\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-81a2889fad504de58095da8917a6b28a css-ur9nhf\" builder-id=\"builder-81a2889fad504de58095da8917a6b28a\"\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-1b9013eea0354cef82e14d66dc05944c builder-has-component css-hgfgng\" builder-id=\"builder-1b9013eea0354cef82e14d66dc05944c\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eAbout the 2A3 Tube: A Legendary Directly Heated Power Triode\u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-5e0292970fc74e4892cd0c140f41baef builder-has-component css-hgfgng\" builder-id=\"builder-5e0292970fc74e4892cd0c140f41baef\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eThe 2A3 tube, a directly heated power triode, has been captivating audiophiles and hifi enthusiasts since its introduction by RCA in the 1930s (and brands like Western Electric and Tung-Sol). This vacuum tube is renowned for its ability to deliver a warm, rich, and naturally textured sound in both power amplifiers and preamplifiers.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-bb459dc909cb45f082cfa66a634f3c87 builder-has-component css-hgfgng\" builder-id=\"builder-bb459dc909cb45f082cfa66a634f3c87\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eAs a low-frequency power triode, the 2A3 vacuum tube is capable of producing a modest yet sufficient power output, typically ranging from 2 to 5 watts per tube in single-ended class A configurations. This makes it an ideal choice for high-quality, low-powered tube amplifiers that prioritize sonics over raw power.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-d596d77a1623497a85b3c61ca930e775 builder-has-component css-hgfgng\" builder-id=\"builder-d596d77a1623497a85b3c61ca930e775\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eThe 2A3's filament, which also serves as the cathode, is directly heated (directly heated triode tube), contributing to its unique sonic characteristics. When paired with suitable transformers and circuitry, the 2A3 power vacuum tube can create an incredibly immersive and emotionally engaging listening experience.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-e0a177dbae0d46c6b180fc7ee3badde9 builder-has-component css-hgfgng\" builder-id=\"builder-e0a177dbae0d46c6b180fc7ee3badde9\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eAudiophiles and hifi enthusiasts in the USA and around the world praise the 2A3 for its ability to reproduce music with a sense of warmth, intimacy, and naturalness that solid-state devices struggle to match. Its rich midrange, smooth treble, and well-controlled bass make it a favorite among those seeking the quintessential \"tube sound.\"\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-7689f309e096496ba7e93cc528520739 builder-has-component css-hgfgng\" builder-id=\"builder-7689f309e096496ba7e93cc528520739\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eMany iconic amplifier designs have been built around the 2A3, cementing its position as a legendary tube in the world of high-end audio. These amplifiers often feature minimal components and simple circuits, allowing the 2A3's inherent qualities to shine through. In terms of specs, the 2A3 typically features a maximum plate dissipation of around 15 watts, a filament voltage of 2.5 volts, and a filament current of 2.5 amps. Its amplification factor is approximately 4.2, and its plate resistance is about 800 ohms.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-bc960cde177941edaca730017cae0f8d builder-has-component css-hgfgng\" builder-id=\"builder-bc960cde177941edaca730017cae0f8d\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eDespite its age, the 2A3 tube remains a popular choice among DIY enthusiasts, boutique tube amp manufacturers, and audio purists who appreciate its timeless design and unrivaled sonic performance. Whether you're building a new tube amplifier or upgrading an existing one, the 2A3 is a vacuum tube that deserves serious consideration.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-5d0cb6e0722e4f2e9c3e43694c35c5a0 css-ur9nhf\" builder-id=\"builder-5d0cb6e0722e4f2e9c3e43694c35c5a0\"\u003e\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"1mvsfya\"\u003e\u003c\/style\u003e\n\u003cimg src=\"https:\/\/cdn.builder.io\/api\/v1\/pixel?apiKey=48d1cdcd52ec4d289f1ef8c4f75da167\" aria-hidden=\"true\" alt=\"\" role=\"presentation\" width=\"0\" height=\"0\" class=\"builder-block builder-pixel-kbluty8e5o8 css-1mvsfya\" builder-id=\"builder-pixel-kbluty8e5o8\"\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\u003c\/div\u003e\u003c\/builder-component\u003e\n\u003cscript async src=\"https:\/\/cdn.builder.io\/js\/webcomponents\"\u003e\u003c\/script\u003e","brand":"KR Audio","offers":[{"title":"Pair ($1150)","offer_id":49668540465466,"sku":"2A3-KRM-1","price":1150.0,"currency_code":"USD","in_stock":true},{"title":"Quad ($2300)","offer_id":49668540498234,"sku":"2A3-KRM-2","price":2300.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0834\/0245\/7402\/files\/KR_Audio_2A3_Tube_Pair__82290.1715874157.1280.1280.jpg?v=1719257330"},{"product_id":"kr-audio-300bxls-tube-pair","title":"300BXLS Vacuum Tube","description":"\u003cbuilder-component rev=\"6de0oihzk2\" api-key=\"48d1cdcd52ec4d289f1ef8c4f75da167\" options='{\"locale\":\"Default\"}' name=\"product-description\" entry=\"2fd675bf3801411aa1c887c22941c157\"\u003e\n\n\u003c!-- ***** Generated by Builder.io on Mon, 08 Jun 2026 19:47:45 GMT ***** --\u003e\n\n\u003cstyle type=\"text\/css\" class=\"builder-styles 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\/*start:121vstx*\/.css-121vstx.builder-block{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;position:relative;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;box-sizing:border-box;margin-top:20px;line-height:normal;height:auto;content-visibility:auto;contain-intrinsic-size:1344px;}@media only screen and (max-width:991px){.css-121vstx.builder-block{content-visibility:auto;contain-intrinsic-size:1344px;}}@media only screen and (max-width:640px){.css-121vstx.builder-block{content-visibility:auto;contain-intrinsic-size:1418px;}}\/*end:121vstx*\/ \/*start:1n465md*\/.css-1n465md.builder-block{height:0;width:0;display:block;opacity:0;overflow:hidden;pointer-events:none;}\/*end:1n465md*\/\u003c\/style\u003e\n\u003cdiv class=\"builder-component builder-component-2fd675bf3801411aa1c887c22941c157\" data-name=\"product-description\" data-source=\"Rendered by Builder.io\"\u003e\u003cdiv class=\"builder-content\" builder-content-id=\"2fd675bf3801411aa1c887c22941c157\" builder-model=\"product-description\"\u003e\u003cdiv data-builder-component=\"product-description\" data-builder-content-id=\"2fd675bf3801411aa1c887c22941c157\" data-builder-variation-id=\"2fd675bf3801411aa1c887c22941c157\"\u003e\n\u003cstyle data-emotion-css=\"h47494\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-blocks css-h47494\" builder-type=\"blocks\"\u003e\n\u003cstyle data-emotion-css=\"rm3vjx\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-f02befaa074446c59e6bcafe1ac45412 builder-has-component css-rm3vjx\" builder-id=\"builder-f02befaa074446c59e6bcafe1ac45412\"\u003e\n\u003cstyle data-emotion-css=\"1840m1q\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-columns css-1840m1q\"\u003e\n\u003cstyle data-emotion-css=\"1ukkadj\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-column css-1ukkadj\"\u003e\u003cdiv class=\"builder-blocks builder-blocks-child css-h47494\" builder-type=\"blocks\" builder-parent-id=\"builder-f02befaa074446c59e6bcafe1ac45412\"\u003e\n\u003cstyle data-emotion-css=\"qcdo0v\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-039ba04ad8cd496788dad845ce63d848 builder-has-component css-qcdo0v\" builder-id=\"builder-039ba04ad8cd496788dad845ce63d848\"\u003e\n\u003cstyle data-emotion-css=\"1qggkls\"\u003e\u003c\/style\u003e\n\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eThe KR Audio 300BXLS Tube Pair is a groundbreaking set of low-frequency, high-power triodes that redefine the limits of what's possible in high-end audio. Designed for the most discerning audiophiles and music enthusiasts, these exceptional tubes deliver an astonishing 15-24 watts of pure class-A power per tube, setting a new standard in performance and musicality.\u003c\/p\u003e\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"hgfgng\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-0ab9f65267cd4b4cbe41beebfb9b6114 builder-has-component css-hgfgng\" builder-id=\"builder-0ab9f65267cd4b4cbe41beebfb9b6114\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eThe KR Audio 300BXLS Tube Pair represents the pinnacle of vacuum tube technology, meticulously crafted to provide an unparalleled listening experience. These state-of-the-art triodes harness the essence of the legendary 300B design while pushing the boundaries of power and finesse to unprecedented levels. With their remarkable power output of 15-24 watts per tube in pure class-A operation, the KR Audio 300BXLS tubes offer an extraordinary level of headroom and dynamic range. This allows your amplifier to effortlessly handle even the most demanding musical passages, reproducing every nuance and detail with breathtaking clarity and authority.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-e269cfddd7284946a1ef7dc3dca66168 builder-has-component css-hgfgng\" builder-id=\"builder-e269cfddd7284946a1ef7dc3dca66168\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eThe 300BXLS's enhanced power delivery is matched by its exceptional linearity and low distortion, resulting in a sound that is both highly transparent and emotionally engaging. These tubes excel at creating a vast and immersive soundstage, placing you at the heart of the musical performance and revealing the subtlest details and textures in your favorite recordings. KR Audio's unwavering commitment to quality is evident in every aspect of the 300BXLS Tube Pair's construction. Each tube is handcrafted using the finest materials and subjected to rigorous testing and matching to ensure optimal performance and reliability. The result is a pair of vacuum tubes that not only sound incredible but also offer the durability and longevity demanded by serious audio enthusiasts.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-7f2049f0a0fa408e8bdc4ea77bf69d5f builder-has-component css-hgfgng\" builder-id=\"builder-7f2049f0a0fa408e8bdc4ea77bf69d5f\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eAbout the 300B Tube: The Legendary Power Triode\u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-1df77ee130e540de8d582ae7eebe3233 builder-has-component css-hgfgng\" builder-id=\"builder-1df77ee130e540de8d582ae7eebe3233\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003e\u003cstrong\u003eNote that the 300BXLS model is a more powerful version of the original 300B, providing 15-24W of power versus the 6-12W of the original.\u003c\/strong\u003e\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"19da917\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-7b053cc57dea48eaad6838139e979614 builder-has-component css-19da917\" builder-id=\"builder-7b053cc57dea48eaad6838139e979614\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003e\u003cstrong\u003eAbout the 300B Tube: The Legendary Power Triode\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe 300B tube, originally designed by Western Electric (WE 300B\/Western Electric 300B) in the 1930s, has become a legendary electron tube in the world of high fidelity audio. Known for its exceptional midrange and high-frequency performance, warm tonal qualities, and ability to deliver a highly musical and engaging listening experience, the 300B has been a favorite among audiophiles and music enthusiasts for decades. As a directly heated power triode, the 300B features a cathode that also serves as the filament, contributing to its unique sonic characteristics. This design allows for a simplified and more efficient electron emission process, resulting in a purer and more lifelike sound quality.\u003c\/p\u003e\n\u003cp\u003eThe 300B's anode, coupled with its high amplification factor and low plate resistance, enables it to deliver a robust and dynamic performance in both single-ended and push-pull amplifier configurations. This versatility has made the 300B a popular choice for a wide range of applications, including power amplifiers, tube amps, integrated amplifiers, and preamplifiers (preamp). While Western Electric's production of the 300B ceased in the 1980s, several manufacturers, such as KR Audio, Electro-Harmonix, and JJ Electronic, have continued to produce high-quality 300B tubes. These new production tubes, like the JJ 300B, aim to capture the essence of the original WE 300B while incorporating modern manufacturing techniques and materials to ensure reliability and consistency. We believe that the KR Audio 300B is the superior version of the 300B tube today.\u003c\/p\u003e\n\u003cp\u003eWhen paired with high-quality transformers and well-designed circuitry, the 300B tube can create an immersive and emotionally engaging listening experience. Its ability to reproduce music with a sense of warmth, smoothness, and natural detail has earned it a reputation as one of the best-sounding power tubes available.\u003c\/p\u003e\n\u003cp\u003eAudiophiles and music lovers in the USA and around the world continue to seek out 300B-based tube amplifiers and preamplifiers for their ability to deliver a truly captivating hi-fi experience. Many manufacturers offer amplifiers designed around the 300B, ranging from single-ended triode (SET) designs to more powerful push-pull configurations.\u003c\/p\u003e\n\u003cp\u003eWhether you're building a new tube amplifier or upgrading an existing one, the 300B tube is an excellent choice for those seeking the ultimate in musical performance, emotional engagement, and the best sound quality. With its rich history, legendary status, and unrivaled sonic qualities, the 300B continues to be a cornerstone of high-end audio.\u003c\/p\u003e\n\u003cp\u003eEnter KR Audio. \u003c\/p\u003e\n\u003cp\u003eKR Audio is one of the world’s top manufacturers of vacuum tubes and high-end vacuum tube amplifiers, all crafted with care right in the beautiful Czech Republic. KR Audio specializes in producing low-frequency power triodes and high-end audio equipment, all made by hand! From selecting the glass to their meticulous artisan work in metal and glass blowing, every step is done with the utmost attention to detail. Their commitment to quality means they never use automated lines—this is what sets KR Audio apart and ensures our products are truly exceptional.\u003c\/p\u003e\n\u003cp\u003eA bit about KR Audio history: KR Audio's journey started in the late 1950s when a young Riccardo Kron, while assisting his professor, became curious about why even the best tubes tended to drift over time. This sparked a lifelong quest to enhance tube performance, a passion he carried through his time at Deutsche Grammophon and Magnadyne. Following the fall of communism, Riccardo teamed up with a talented research and development group from TESLA LABORATORIES in the Czech Republic. Together, they pioneered the creation of hand-crafted vacuum tubes designed specifically for audio, utilizing improved materials, higher vacuum levels, and rigorous quality control. The result? Tubes that deliver incredible dynamics, finer resolution, and an almost tangible sound experience.\u003c\/p\u003e\n\u003cp\u003eKR AUDIO Electronic SRO began as a tube manufacturer and has since evolved into a developer of world-class amplifiers, employing a unique reverse hybrid system to enhance your listening experience. Thank you for considering KR Audio—we're excited to share KR Audio's passion for high-quality sound with you!\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"15auezb\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-b9c7c5f20e2a43b9a2f2a7bffe341888 builder-has-component css-15auezb\" builder-id=\"builder-b9c7c5f20e2a43b9a2f2a7bffe341888\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eKR Audio WARRANTY ON TUBES ONLY\u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"r6fcn8\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-b15340b081e44a13815c2640e72b5e09 builder-has-component css-r6fcn8\" builder-id=\"builder-b15340b081e44a13815c2640e72b5e09\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003ePlease take a moment to return your warranty registration form included with the tubes. Unregistered KR tubes will not be warranted. Customers must return the warranty registration when the tubes have been received. \u003c\/p\u003e\n\u003cp\u003eKR Audio Electronics will respect valid warranty claims. Incorrect claims or late warranty registration will void any guarantee. KR Audio Electronics will replace the tube provided the following conditions are met: 1) The tubes were used according to the technical data sheet enclosed with the KR tube. 2) Abuse, accident or unauthorized use of the tube will be determined by KR Audio Electronics. 3) All tubes to be returned with the original factory box and warranty. 4) To obtain a replacement for a faulty tube, KR Audio Electronics reserves the right to obtain dealer or distributor authorization prior to shipping products pre-paid back to us. \u003c\/p\u003e\n\u003cp\u003eKR Audio Electronics gives a one-year warranty for your tube from the date of purchase. The purchase date should be written or stamped by the dealer or distributor on the day you buy the tube. Only expert technicians can change the work point of the tube. Improper use of the tube or incorrect application of the tube to a circuit cannot be covered by our warranty.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"rkf76a\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-29bac790a9e84351a8a5a8de772c3f65 builder-has-component css-rkf76a\" builder-id=\"builder-29bac790a9e84351a8a5a8de772c3f65\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eMoon Audio Tube Testing Process\u003c\/h3\u003e\n\u003cp\u003eOur high-end audio systems achieve sonic purity through the use of carefully selected NOS vacuum tubes. We take time to search for NOS tubes, understanding their unique potential for audio reproduction. Each tube is rigorously tested using legendary HICKOK 800K 600K Dynamic Mutual Conductance Tube Tester and TV7-A\/U Vacuum Tube Testers to measure critical parameters, including mutual conductance, emission, and gas levels. By precisely matching tubes based on these measurements, we deliver balanced, dynamic, and lifelike audio that elevates your listening experience to an art form.  \u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-b5ccb4ed36074009ae6ec517ed2be230 builder-has-component css-15auezb\" builder-id=\"builder-b5ccb4ed36074009ae6ec517ed2be230\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eFAQ\u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"121vstx\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-dd80f2ab081543d79c7296a659cc9fe0 builder-has-component css-121vstx\" builder-id=\"builder-dd80f2ab081543d79c7296a659cc9fe0\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003e\u003cstrong\u003eWhat is a 300B tube and how does it work?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe 300B is a directly heated triode vacuum tube used in audio amplification. It operates by passing an electric current through a heated cathode to emit electrons, which are then controlled by a grid to amplify the input signal.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat amplifiers use the 300B tube?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe 300B tube is commonly found in single-ended triode (SET) amplifiers renowned for their rich, warm sound signature. Many high-end audio manufacturers like \u003ca href=\"https:\/\/www.moon-audio.pro\/brands\/kr_audio.html\" rel=\"noopener noreferrer\" target=\"_blank\"\u003eKR Audio\u003c\/a\u003e produce amplifiers utilizing the 300B tube for audiophile-grade sound reproduction.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat are the sonic characteristics of the 300B tube?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe 300B tube is prized for its lush midrange, smooth treble, and natural timbre. It delivers a musical, euphonic sound signature with a captivating sense of realism and intimacy.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I replace the 300B tube in my amplifier with a different type?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eWhile some amplifiers allow tube rolling, it's essential to consult the manufacturer's specifications and recommendations. Substituting the 300B tube with a different type may alter the \u003ca href=\"https:\/\/www.moon-audio.pro\/headphone-amplifiers-dacs\/amplifiers.html\" rel=\"noopener noreferrer\" target=\"_blank\"\u003eamplifier's\u003c\/a\u003e performance and sound characteristics.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow long does a 300B tube typically last?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA: The lifespan of a 300B tube varies depending on usage, operating conditions, and tube quality. On average, a well-maintained 300B tube can last several thousand hours before requiring replacement.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow do I bias a 300B tube amplifier?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA: Biasing a 300B tube amplifier involves adjusting the bias voltage to ensure proper operating conditions and optimal performance. Consult the \u003ca href=\"https:\/\/www.moon-audio.pro\/headphone-amplifiers-dacs\/amplifiers.html\" rel=\"noopener noreferrer\" target=\"_blank\"\u003eamplifier's\u003c\/a\u003e user manual or seek assistance from a qualified technician for precise biasing procedures. Feel free to \u003ca href=\"https:\/\/www.moon-audio.pro\/contact-us\" rel=\"noopener noreferrer\" target=\"_blank\"\u003eContact Us\u003c\/a\u003e and we'll be more than happy to assist you.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat are the pros and cons of using a 300B tube amplifier?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eA: Pros include exceptional sound quality, musicality, and compatibility with high-efficiency speakers. Cons may include higher cost, lower power output compared to other tube types, and the need for occasional tube replacement.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eAre there different brands or versions of the 300B tube?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eYes, various manufacturers produce 300B tubes, each with unique construction, materials, and sonic characteristics. Popular brands include Western Electric, \u003ca href=\"https:\/\/www.moon-audio.pro\/brands\/kr_audio.html\" rel=\"noopener noreferrer\" target=\"_blank\"\u003eKR Audio\u003c\/a\u003e, TJ Full Music, Sophia Electric, and Shuguang.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat are the differences between vintage and modern production 300B tubes?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eVintage 300B tubes are highly sought after for their historical significance and reputed sound quality. Modern production tubes offer advancements in manufacturing techniques and may provide improved reliability and consistency.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow do I select the right 300B tube for my amplifier?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eConsider factors such as brand reputation, sonic preferences, budget, and compatibility with your amplifier. Researching reviews, seeking advice from audio enthusiasts, and experimenting with different tubes can help you find the perfect match for your system. We consider the version by \u003ca href=\"https:\/\/www.moon-audio.pro\/brands\/kr_audio.html\" rel=\"noopener noreferrer\" target=\"_blank\"\u003eKR Audio\u003c\/a\u003e to be one of the best on the market.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"1n465md\"\u003e\u003c\/style\u003e\n\u003cimg src=\"https:\/\/cdn.builder.io\/api\/v1\/pixel?apiKey=48d1cdcd52ec4d289f1ef8c4f75da167\" aria-hidden=\"true\" alt=\"\" role=\"presentation\" width=\"0\" height=\"0\" class=\"builder-block builder-pixel-0mkklfbcqcpi css-1n465md\" builder-id=\"builder-pixel-0mkklfbcqcpi\"\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\u003c\/div\u003e\u003c\/builder-component\u003e\n\u003cscript async src=\"https:\/\/cdn.builder.io\/js\/webcomponents\"\u003e\u003c\/script\u003e","brand":"KR Audio","offers":[{"title":"Pair ($1600)","offer_id":49668486988090,"sku":"300BXLS-KRM-1","price":1600.0,"currency_code":"USD","in_stock":true},{"title":"Quad ($3200)","offer_id":49668487020858,"sku":"300BXLS-KRM-2","price":3200.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0834\/0245\/7402\/files\/KR_Audio_300BXLS_Tube_Pair__59600.1715880141.1280.1280.jpg?v=1719257335"},{"product_id":"kr-audio-5u4g-tube-single","title":"5U4G Rectifier Vacuum Tube","description":"\u003cbuilder-component rev=\"d8zq5u3tlu\" api-key=\"48d1cdcd52ec4d289f1ef8c4f75da167\" options='{\"locale\":\"Default\"}' name=\"product-description\" entry=\"97a6e9bd3b8b40fb8e1f54c90e7dce79\"\u003e\n\n\u003c!-- ***** Generated by Builder.io on Mon, 08 Jun 2026 19:46:32 GMT ***** --\u003e\n\n\u003cstyle type=\"text\/css\" class=\"builder-styles 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\/*start:1t1j4rm*\/.css-1t1j4rm.builder-block{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;position:relative;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;box-sizing:border-box;margin-top:20px;line-height:normal;height:auto;content-visibility:auto;contain-intrinsic-size:1104px;}@media only screen and (max-width:991px){.css-1t1j4rm.builder-block{content-visibility:auto;contain-intrinsic-size:1104px;}}@media only screen and (max-width:640px){.css-1t1j4rm.builder-block{content-visibility:auto;contain-intrinsic-size:1035px;}}\/*end:1t1j4rm*\/ \/*start:1n465md*\/.css-1n465md.builder-block{height:0;width:0;display:block;opacity:0;overflow:hidden;pointer-events:none;}\/*end:1n465md*\/\u003c\/style\u003e\n\u003cdiv class=\"builder-component builder-component-97a6e9bd3b8b40fb8e1f54c90e7dce79\" data-name=\"product-description\" data-source=\"Rendered by Builder.io\"\u003e\u003cdiv class=\"builder-content\" builder-content-id=\"97a6e9bd3b8b40fb8e1f54c90e7dce79\" builder-model=\"product-description\"\u003e\u003cdiv data-builder-component=\"product-description\" data-builder-content-id=\"97a6e9bd3b8b40fb8e1f54c90e7dce79\" data-builder-variation-id=\"97a6e9bd3b8b40fb8e1f54c90e7dce79\"\u003e\n\u003cstyle data-emotion-css=\"h47494\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-blocks css-h47494\" builder-type=\"blocks\"\u003e\n\u003cstyle data-emotion-css=\"rm3vjx\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-9d258df253e049a7bd2b46ca1df595ae builder-has-component css-rm3vjx\" builder-id=\"builder-9d258df253e049a7bd2b46ca1df595ae\"\u003e\n\u003cstyle data-emotion-css=\"1840m1q\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-columns css-1840m1q\"\u003e\n\u003cstyle data-emotion-css=\"1ukkadj\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-column css-1ukkadj\"\u003e\u003cdiv class=\"builder-blocks builder-blocks-child css-h47494\" builder-type=\"blocks\" builder-parent-id=\"builder-9d258df253e049a7bd2b46ca1df595ae\"\u003e\n\u003cstyle data-emotion-css=\"hgfgng\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-4d4cb20376c64b79bfc01630be7ee375 builder-has-component css-hgfgng\" builder-id=\"builder-4d4cb20376c64b79bfc01630be7ee375\"\u003e\n\u003cstyle data-emotion-css=\"1qggkls\"\u003e\u003c\/style\u003e\n\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eThe KR Audio 5U4G rectifier tube is a high-end full-wave thermionic vacuum tube that sets the standard for exceptional performance and audiophile-grade sound quality. This meticulously crafted tube is designed to elevate your audio experience by providing a stable, regular voltage and superior current rectification, ensuring that your amplifier delivers the rich, detailed sound you demand. Ideal for use in tube amps, guitar amps (Fender, Mesa Boogie), preamp tubes, and pedals, the KR Audio 5U4G is a versatile addition to any hi-fi setup.\u003c\/p\u003e\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-2878dd26fc444b299f57e71752579f97 builder-has-component css-hgfgng\" builder-id=\"builder-2878dd26fc444b299f57e71752579f97\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eThe KR Audio 5U4G is the result of years of research and development, combining advanced engineering with the finest materials and filaments to create a rectifier tube that stands head and shoulders above the competition. Its superior design ensures long life and reliable operation, making it the perfect choice for discerning audiophiles who refuse to compromise on sound quality. At the heart of the KR Audio 5U4G's outstanding performance is its ability to deliver a stable, regular voltage to your amplifier's circuit. By providing a clean and consistent power supply, this tube allows your amplifier to operate at its full potential, reproducing music with unparalleled clarity, dynamics, and emotional impact. \u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-3b04d58bbd0f4d6f9508f96fd2fa1b63 builder-has-component css-hgfgng\" builder-id=\"builder-3b04d58bbd0f4d6f9508f96fd2fa1b63\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eThe 5U4G's excellent current rectification capabilities ensure that your amplifier has the necessary power to handle even the most demanding musical passages with ease. This tube's superior rectification process minimizes voltage drops and reduces noise, resulting in a cleaner, more transparent sound that brings out the best in your favorite recordings. Available in variations such as the jj5u4gb rectifier vacuum tube, 5U4GA, and GE 5U4GB RCA, and produced by renowned manufacturers like Electro-Harmonix, KR Audio, Sylvania, Mullard, JJ Electronic, and Tung-Sol, this new production tube maintains the heritage of high-quality USA-made power tubes. We consider the KR Audio version one of the best on the market. \u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"ur9nhf\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-f85d7cfcf3f248038ac9a0e470dba576 css-ur9nhf\" builder-id=\"builder-f85d7cfcf3f248038ac9a0e470dba576\"\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-2905baeb8f2d497996ca5fb40a443cbb builder-has-component css-hgfgng\" builder-id=\"builder-2905baeb8f2d497996ca5fb40a443cbb\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eThe Legacy and Popularity of the 5U4 Tube\u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"1xes42u\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-b89806d718314b4fb8aed5e474a8a612 builder-has-component css-1xes42u\" builder-id=\"builder-b89806d718314b4fb8aed5e474a8a612\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eThe 5U4 tube, a venerable component in the world of audio electronics, boasts a rich history that dates back to the golden age of tube amplifiers. First introduced in the early 20th century, the 5U4 tube quickly became a standard for full-wave rectification in high-fidelity audio systems and professional audio equipment. Its ability to convert alternating current (AC) to direct current (DC) efficiently and reliably made it an indispensable component in ensuring the smooth operation of tube amplifiers.\u003c\/p\u003e\n\u003cp\u003eOver the decades, the 5U4 tube has earned a reputation for its durability, stability, and superior performance. Its robust design allows it to handle high current loads while maintaining a steady and regular voltage output, which is crucial for preserving the integrity of audio signals. This reliability has made the 5U4 a favorite among audiophiles and audio engineers who seek to maintain the highest standards in sound quality.\u003c\/p\u003e\n\u003cp\u003eThe resurgence of interest in vintage audio equipment and high-fidelity sound systems has further cemented the 5U4 tube's popularity. Audiophiles appreciate the tube's ability to contribute to a warm, rich sound that many find lacking in modern solid-state devices. The 5U4 tube is often lauded for its role in delivering a natural, detailed audio experience that enhances the subtleties of music playback.\u003c\/p\u003e\n\u003cp\u003eToday, the 5U4 tube remains a sought-after component for those looking to achieve an authentic, high-quality audio experience. Its enduring legacy is a testament to its exceptional performance and the timeless appeal of tube-based audio technology. As more audiophiles continue to seek out the best possible components for their systems, the 5U4 tube's popularity shows no signs of waning, solidifying its place as a cornerstone in the world of high-fidelity audio.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-63f9ad7dc84b4adebe5eab494c410a0d css-ur9nhf\" builder-id=\"builder-63f9ad7dc84b4adebe5eab494c410a0d\"\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"5yng5f\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-6d00a93682044e16acebb28df2ad200c builder-has-component css-5yng5f\" builder-id=\"builder-6d00a93682044e16acebb28df2ad200c\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eKR Audio WARRANTY ON TUBES ONLY\u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"qj5sun\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-97ff6ce109ba406b9828269999fa4be8 builder-has-component css-qj5sun\" builder-id=\"builder-97ff6ce109ba406b9828269999fa4be8\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003ePlease take a moment to return your warranty registration form included with the tubes. Unregistered KR tubes will not be warranted. Customers must return the warranty registration when the tubes have been received. \u003c\/p\u003e\n\u003cp\u003eKR Audio Electronics will respect valid warranty claims. Incorrect claims or late warranty registration will void any guarantee. KR Audio Electronics will replace the tube provided the following conditions are met: \u003c\/p\u003e\n\u003col\u003e\n\u003cli\u003eThe tubes were used according to the technical data sheet enclosed with the KR tube. \u003c\/li\u003e\n\u003cli\u003eAbuse, accident or unauthorized use of the tube will be determined by KR Audio Electronics. \u003c\/li\u003e\n\u003cli\u003eAll tubes to be returned with the original factory box and warranty. \u003c\/li\u003e\n\u003cli\u003eTo obtain a replacement for a faulty tube, KR Audio Electronics reserves the right to obtain dealer or distributor authorization prior to shipping products pre-paid back to us. \u003c\/li\u003e\n\u003c\/ol\u003e\n\u003cp\u003eKR Audio Electronics gives a one-year warranty for your tube from the date of purchase. The purchase date should be written or stamped by the dealer or distributor on the day you buy the tube. Only expert technicians can change the work point of the tube. Improper use of the tube or incorrect application of the tube to a circuit cannot be covered by our warranty. \u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-96e625b451374a96aa994e4c68de4e08 builder-has-component css-hgfgng\" builder-id=\"builder-96e625b451374a96aa994e4c68de4e08\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eMoon Audio Tube Testing Process\u003c\/h3\u003e\n\u003cp\u003eOur high-end audio systems achieve sonic purity through the use of carefully selected NOS vacuum tubes. We take time to search for NOS tubes, understanding their unique potential for audio reproduction. Each tube is rigorously tested using legendary HICKOK 800K 600K Dynamic Mutual Conductance Tube Tester and TV7-A\/U Vacuum Tube Testers to measure critical parameters, including mutual conductance, emission, and gas levels. By precisely matching tubes based on these measurements, we deliver balanced, dynamic, and lifelike audio that elevates your listening experience to an art form.  \u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-758d3691bd614a8e9908040a05a1af5f css-ur9nhf\" builder-id=\"builder-758d3691bd614a8e9908040a05a1af5f\"\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-a1df7b4c908e459292e78124b9e721be builder-has-component css-5yng5f\" builder-id=\"builder-a1df7b4c908e459292e78124b9e721be\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eFAQ\u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"1t1j4rm\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-03cfd6af833845d585fb5f1b82a21d40 builder-has-component css-1t1j4rm\" builder-id=\"builder-03cfd6af833845d585fb5f1b82a21d40\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003e\u003cstrong\u003eWhat is a 5U4 rectifier tube and what does it do?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe 5U4 rectifier tube is a full-wave thermionic tube used to convert AC to DC, providing stable voltage for audio equipment and ensuring smooth operation of tube amplifiers.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat are the differences between 5U4 and other rectifier tubes?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe 5U4 tube is known for its robustness and ability to handle high current loads, while other rectifier tubes like the 5AR4 or GZ34 might offer different voltage drops or current capacities.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhy is the 5U4 tube popular among audiophiles?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eAudiophiles favor the 5U4 tube for its ability to contribute to a warm, rich sound quality and its reputation for reliability and long life in high-fidelity audio systems.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow do I know if my equipment is compatible with a 5U4 rectifier tube?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eCheck the specifications of your audio equipment or consult the manufacturer's documentation to ensure compatibility with the 5U4 tube.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat are the benefits of using a 5U4 rectifier tube in my amplifier?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eBenefits include stable voltage output, improved sound quality, and enhanced performance and longevity of the amplifier.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow long does a 5U4 rectifier tube typically last?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe lifespan of a 5U4 tube varies based on usage and operating conditions but can often last several years due to its robust construction.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I replace a 5U4 rectifier tube myself, or do I need a professional?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eWhile some experienced users can replace a 5U4 tube themselves, it is often recommended to seek professional assistance to avoid damaging the equipment or the new tube.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat are the signs that my 5U4 rectifier tube needs replacing?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSigns include noticeable drops in audio performance, increased hum or noise, or visible damage to the tube itself, such as burn marks or cracks.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eAre there different versions or brands of 5U4 tubes, and do they vary in quality?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eYes, various manufacturers produce 5U4 tubes, and quality can vary. Researching and selecting reputable brands is crucial for optimal performance. We believe the KR Audio version of the 5U4G tube is one of the best on the market.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"1n465md\"\u003e\u003c\/style\u003e\n\u003cimg src=\"https:\/\/cdn.builder.io\/api\/v1\/pixel?apiKey=48d1cdcd52ec4d289f1ef8c4f75da167\" aria-hidden=\"true\" alt=\"\" role=\"presentation\" width=\"0\" height=\"0\" class=\"builder-block builder-pixel-0io6q0o11k64 css-1n465md\" builder-id=\"builder-pixel-0io6q0o11k64\"\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\u003c\/div\u003e\u003c\/builder-component\u003e\n\u003cscript async src=\"https:\/\/cdn.builder.io\/js\/webcomponents\"\u003e\u003c\/script\u003e","brand":"KR Audio","offers":[{"title":"Single ($675)","offer_id":49668337074490,"sku":"5U4G-KR-1","price":675.0,"currency_code":"USD","in_stock":true},{"title":"Matched Pair ($1350)","offer_id":49668337107258,"sku":"5U4G-KR-2","price":1350.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0834\/0245\/7402\/files\/5U4GTubeSingle.jpg?v=1780514559"},{"product_id":"kt88-tube-pair","title":"KT88 Vacuum Tube","description":"\u003cbuilder-component rev=\"t0nt535te\" api-key=\"48d1cdcd52ec4d289f1ef8c4f75da167\" options='{\"locale\":\"Default\"}' name=\"product-description\" entry=\"20da574fba79419b8c4764b345472f5e\"\u003e\n\n\u003c!-- ***** Generated by Builder.io on Mon, 08 Jun 2026 19:45:24 GMT ***** --\u003e\n\n\u003cstyle type=\"text\/css\" class=\"builder-styles builder-api-styles\"\u003e\/*start:h47494*\/.css-h47494{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;-webkit-align-items:stretch;-webkit-box-align:stretch;-ms-flex-align:stretch;align-items:stretch;}\/*end:h47494*\/ 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\/*start:1k5hlgl*\/.css-1k5hlgl.builder-block{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;position:relative;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;box-sizing:border-box;margin-top:20px;line-height:normal;height:auto;content-visibility:auto;contain-intrinsic-size:1152px;}@media only screen and (max-width:991px){.css-1k5hlgl.builder-block{content-visibility:auto;contain-intrinsic-size:1152px;}}@media only screen and (max-width:640px){.css-1k5hlgl.builder-block{content-visibility:auto;contain-intrinsic-size:1125px;}}\/*end:1k5hlgl*\/ \/*start:1n465md*\/.css-1n465md.builder-block{height:0;width:0;display:block;opacity:0;overflow:hidden;pointer-events:none;}\/*end:1n465md*\/\u003c\/style\u003e\n\u003cdiv class=\"builder-component builder-component-20da574fba79419b8c4764b345472f5e\" data-name=\"product-description\" data-source=\"Rendered by Builder.io\"\u003e\u003cdiv class=\"builder-content\" builder-content-id=\"20da574fba79419b8c4764b345472f5e\" builder-model=\"product-description\"\u003e\u003cdiv data-builder-component=\"product-description\" data-builder-content-id=\"20da574fba79419b8c4764b345472f5e\" data-builder-variation-id=\"20da574fba79419b8c4764b345472f5e\"\u003e\n\u003cstyle data-emotion-css=\"h47494\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-blocks css-h47494\" builder-type=\"blocks\"\u003e\n\u003cstyle data-emotion-css=\"rm3vjx\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-f6a11e12500645a68b927c7fe183224e builder-has-component css-rm3vjx\" builder-id=\"builder-f6a11e12500645a68b927c7fe183224e\"\u003e\n\u003cstyle data-emotion-css=\"1840m1q\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-columns css-1840m1q\"\u003e\n\u003cstyle data-emotion-css=\"1ukkadj\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-column css-1ukkadj\"\u003e\u003cdiv class=\"builder-blocks builder-blocks-child css-h47494\" builder-type=\"blocks\" builder-parent-id=\"builder-f6a11e12500645a68b927c7fe183224e\"\u003e\n\u003cstyle data-emotion-css=\"hgfgng\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-f98086868c1c446aa4535816406fca21 builder-has-component css-hgfgng\" builder-id=\"builder-f98086868c1c446aa4535816406fca21\"\u003e\n\u003cstyle data-emotion-css=\"1qggkls\"\u003e\u003c\/style\u003e\n\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eThe KR Audio KT88 Tube Pair is a low-frequency power beam tetrode that delivers an impressive 15-25 watts of pure class-A power per tube. Designed for audiophiles and music enthusiasts who demand the very best in sound quality and performance, these power tubes are the perfect choice for those seeking to elevate their audio experience to new heights. The KR Audio KT88 Tube Pair is meticulously crafted using the finest materials and state-of-the-art manufacturing techniques, ensuring exceptional durability and reliability. Each tube undergoes rigorous testing and quality control measures to guarantee optimal performance and consistency, making them a trusted choice for discerning audio enthusiasts.\u003c\/p\u003e\n\u003cp\u003eWith their remarkable power output of 15-25 watts per tube in pure class-A operation, the KR Audio KT88 tubes provide ample headroom and dynamic range, allowing your amplifier to effortlessly handle even the most demanding musical passages. This robust power delivery, combined with the KT88's inherent linearity and low distortion, results in a listening experience that is both engaging and true to the original recording. The KR Audio KT88 Tube Pair excels at reproducing music with exceptional clarity, warmth, and detail. These tubes offer a wide and deep soundstage, precise imaging, and a natural, lifelike presentation of instruments and vocals. Whether you're enjoying your favorite jazz trio, a symphony orchestra, or a rock band, the KT88 tubes deliver a captivating and immersive audio experience.\u003c\/p\u003e\n\u003cp\u003eThe versatility of the KR Audio KT88 Tube Pair makes them suitable for a wide range of amplifier designs, from single-ended to push-pull configurations. Their compatibility with various circuit topologies allows audio engineers and DIY enthusiasts to explore the full potential of these exceptional power vacuum tubes in their projects. Perfect for tube amps, guitar amplifiers (Ampeg, Marshall, etc.), and hi-fi systems, the brand new KT88 tubes reissue brings the best of both vintage and modern sound to your preamp or power amp setup. Made in the Czech Republic, these tubes stand out for their superior performance and reliability, making them a valuable addition to any high-fidelity audio system.\u003c\/p\u003e\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"ur9nhf\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-1f52433fdc594d739a2410e6c4633938 css-ur9nhf\" builder-id=\"builder-1f52433fdc594d739a2410e6c4633938\"\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"f0aiah\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-7097e2d9d2b248a39c87c8ae8ea8c316 builder-has-component css-f0aiah\" builder-id=\"builder-7097e2d9d2b248a39c87c8ae8ea8c316\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eA Short History of the KT88\u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"1vz5vg3\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-a45d8ca3d5c44ce2bde5169fba5a16bf builder-has-component css-1vz5vg3\" builder-id=\"builder-a45d8ca3d5c44ce2bde5169fba5a16bf\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eThe KT88 tube has a storied history and an enduring popularity among audiophiles and music enthusiasts. Introduced in 1956 by the British company GEC (General Electric Company), the KT88 was designed to compete with the American 6550 tube, offering higher power output and improved performance characteristics. Its robust construction and high power-handling capabilities made it an immediate favorite in the world of high-fidelity audio.\u003c\/p\u003e\n\u003cp\u003eOver the decades, the KT88 became synonymous with powerful, clear, and dynamic sound, making it a staple in many high-end tube amplifiers. Audiophiles particularly appreciate the KT88 for its ability to deliver rich, warm tones with excellent midrange clarity and extended bass response. This tube's sonic qualities are especially prized in both stereo and monoblock amplifier configurations, where its high output and low distortion can be fully appreciated.\u003c\/p\u003e\n\u003cp\u003eThe KT88's popularity surged again in the late 20th and early 21st centuries with the revival of interest in vacuum tube audio equipment. Modern manufacturers such as KR Audio, JJ Electronic, Electro-Harmonix, Telefunken, and Shuguang have continued to produce high-quality KT88 tubes, ensuring their availability for contemporary audio enthusiasts. These new production tubes maintain the legacy of their predecessors while incorporating advancements in materials and manufacturing techniques to enhance reliability and performance.\u003c\/p\u003e\n\u003cp\u003eAudiophiles often seek out the KT88 (KR Audio KT88, JJ KT88, Mullard KT88, Genalex Gold Lion KT88, KT88-T) for its ability to bring out the best in high-fidelity audio systems, whether for listening to vinyl records, streaming high-resolution audio, or enhancing the sound of electric guitars and basses. Its versatility and superior sound quality have cemented the KT88's place as a legendary component in the audiophile community, continuing to inspire and satisfy listeners around the world.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-c758bc7ccf0f4ba2bfcc1c05b060b204 css-ur9nhf\" builder-id=\"builder-c758bc7ccf0f4ba2bfcc1c05b060b204\"\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"15auezb\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-ec80df22289549cf8bbbc6850e9e8fac builder-has-component css-15auezb\" builder-id=\"builder-ec80df22289549cf8bbbc6850e9e8fac\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eKR Audio WARRANTY ON TUBES ONLY\u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"1etrf42\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-57d68413d65743c1b499fe2a74bd0bf8 builder-has-component css-1etrf42\" builder-id=\"builder-57d68413d65743c1b499fe2a74bd0bf8\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003ePlease take a moment to return your warranty registration form included with the tubes. Unregistered KR tubes will not be warranted. Customers must return the warranty registration when the tubes have been received. \u003c\/p\u003e\n\u003cp\u003eKR Audio Electronics will respect valid warranty claims. Incorrect claims or late warranty registration will void any guarantee. KR Audio Electronics will replace the tube provided the following conditions are met: \u003c\/p\u003e\n\u003col\u003e\n\u003cli\u003eThe tubes were used according to the technical data sheet enclosed with the KR tube. \u003c\/li\u003e\n\u003cli\u003eAbuse, accident or unauthorized use of the tube will be determined by KR Audio Electronics. \u003c\/li\u003e\n\u003cli\u003eAll tubes to be returned with the original factory box and warranty. \u003c\/li\u003e\n\u003cli\u003eTo obtain a replacement for a faulty tube, KR Audio Electronics reserves the right to obtain dealer or distributor authorization prior to shipping products pre-paid back to us. \u003c\/li\u003e\n\u003c\/ol\u003e\n\u003cp\u003eKR Audio Electronics gives a one-year warranty for your tube from the date of purchase. The purchase date should be written or stamped by the dealer or distributor on the day you buy the tube. Only expert technicians can change the work point of the tube. Improper use of the tube or incorrect application of the tube to a circuit cannot be covered by our warranty. \u003c\/p\u003e\n\u003ch3\u003e\u003cbr\u003e\u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"p548tv\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-42b01bf785cf4611a3465525faba6e63 builder-has-component css-p548tv\" builder-id=\"builder-42b01bf785cf4611a3465525faba6e63\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eMoon Audio Tube Testing Process\u003c\/h3\u003e\n\u003cp\u003eOur high-end audio systems achieve sonic purity through the use of carefully selected NOS vacuum tubes. We take time to search for NOS tubes, understanding their unique potential for audio reproduction. Each tube is rigorously tested using legendary HICKOK 800K 600K Dynamic Mutual Conductance Tube Tester and TV7-A\/U Vacuum Tube Testers to measure critical parameters, including mutual conductance, emission, and gas levels. By precisely matching tubes based on these measurements, we deliver balanced, dynamic, and lifelike audio that elevates your listening experience to an art form.  \u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-075c5296b9314e4093dce582ac139b60 css-ur9nhf\" builder-id=\"builder-075c5296b9314e4093dce582ac139b60\"\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-9199972f680d417283c02d3364e0f3b0 builder-has-component css-15auezb\" builder-id=\"builder-9199972f680d417283c02d3364e0f3b0\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eFAQ\u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"1k5hlgl\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-06abd69b190641c88738b82a94f9003d builder-has-component css-1k5hlgl\" builder-id=\"builder-06abd69b190641c88738b82a94f9003d\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003e\u003cstrong\u003eWhat is a KT88 tube?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe KT88 is a beam tetrode vacuum tube known for its high power output and excellent sound quality, often used in high-fidelity audio amplifiers and some guitar amps.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow does the KT88 compare to the 6550 tube?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe KT88 typically offers higher power output, better bass response, and a warmer sound compared to the 6550, which is often more neutral and has a slightly different tonal character.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat are the best KT88 tubes available today?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003ePopular KT88 tubes include those made by JJ Electronic, KR Audio, Electro-Harmonix, Tung-Sol, and Gold Lion, each offering variations in tonal characteristics and build quality. We think the version by KR Audio is one of the best on the market.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I use KT88 tubes in my amplifier?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eIt depends on your amplifier's design and specifications. Many amplifiers can use KT88 tubes, but it’s important to check with the manufacturer or refer to the amplifier's manual.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is the typical lifespan of a KT88 tube?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eWith proper use and maintenance, a KT88 tube can last between 2,000 to 5,000 hours, though this can vary based on factors such as usage patterns and amplifier settings.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow do KT88 tubes affect sound quality?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eKT88 tubes are known for their rich, warm sound with excellent midrange clarity and powerful bass. They enhance the overall sound quality by providing detailed and dynamic audio reproduction.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eAre KT88 tubes interchangeable with EL34 tubes?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo, KT88 and EL34 tubes are not directly interchangeable due to differences in pin configuration, power requirements, and electrical characteristics. However, some amplifiers are designed to accommodate both with adjustments.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow do I bias KT88 tubes in my amplifier?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eBiasing KT88 tubes requires setting the correct bias voltage according to your amplifier’s specifications. It’s best done using a multimeter and following the amplifier manufacturer’s instructions or by a qualified technician.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat are the signs that my KT88 tubes need replacing?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eSigns that KT88 tubes may need replacing include a noticeable drop in sound quality, increased noise or distortion, reduced output power, or visible signs of wear and tear such as discoloration or internal component damage.\u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"1n465md\"\u003e\u003c\/style\u003e\n\u003cimg src=\"https:\/\/cdn.builder.io\/api\/v1\/pixel?apiKey=48d1cdcd52ec4d289f1ef8c4f75da167\" aria-hidden=\"true\" alt=\"\" role=\"presentation\" width=\"0\" height=\"0\" class=\"builder-block builder-pixel-cx5xhqfkd6j css-1n465md\" builder-id=\"builder-pixel-cx5xhqfkd6j\"\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\u003c\/div\u003e\u003c\/builder-component\u003e\n\u003cscript async src=\"https:\/\/cdn.builder.io\/js\/webcomponents\"\u003e\u003c\/script\u003e","brand":"KR Audio","offers":[{"title":"Pair ($800)","offer_id":49668425449786,"sku":"KT88-KRM-1","price":800.0,"currency_code":"USD","in_stock":true},{"title":"Quad ($1600)","offer_id":49668425482554,"sku":"KT88-KRM-2","price":1600.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0834\/0245\/7402\/files\/KR_Audio_KT88_Tube_Pair__02149.1715881604.1280.1280.jpg?v=1719257638"},{"product_id":"274b-vacuum-tube","title":"274B Rectifier Vacuum Tube","description":"\u003cbuilder-component rev=\"dg6zwep6g1e\" api-key=\"48d1cdcd52ec4d289f1ef8c4f75da167\" options='{\"locale\":\"Default\"}' name=\"product-description\" entry=\"fce05cc567b44bf5a38c469ad843e87c\"\u003e\n\n\u003c!-- ***** Generated by Builder.io on Fri, 18 Jul 2025 14:47:17 GMT ***** --\u003e\n\n\u003cstyle type=\"text\/css\" class=\"builder-styles builder-api-styles\"\u003e\/*start:h47494*\/.css-h47494{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;-webkit-align-items:stretch;-webkit-box-align:stretch;-ms-flex-align:stretch;align-items:stretch;}\/*end:h47494*\/ \/*start:1t2m0n6*\/.css-1t2m0n6.builder-block{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;position:relative;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;box-sizing:border-box;margin-top:0px;margin-right:200px;margin-left:200px;}@media only screen and (max-width:640px){.css-1t2m0n6.builder-block{margin-right:0px;margin-left:0px;}}\/*end:1t2m0n6*\/ \/*start:1840m1q*\/.css-1840m1q{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;}@media (max-width:999px){.css-1840m1q{-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;-webkit-align-items:stretch;-webkit-box-align:stretch;-ms-flex-align:stretch;align-items:stretch;}}\/*end:1840m1q*\/ \/*start:1ukkadj*\/.css-1ukkadj{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;-webkit-align-items:stretch;-webkit-box-align:stretch;-ms-flex-align:stretch;align-items:stretch;line-height:normal;width:calc(100% - 0px);margin-left:0;}.css-1ukkadj \u003e .builder-blocks{-webkit-box-flex:1;-webkit-flex-grow:1;-ms-flex-positive:1;flex-grow:1;}@media (max-width:999px){.css-1ukkadj{width:100%;margin-left:0;}}\/*end:1ukkadj*\/ \/*start:hgfgng*\/.css-hgfgng.builder-block{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;position:relative;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;box-sizing:border-box;margin-top:20px;line-height:normal;height:auto;}\/*end:hgfgng*\/ \/*start:1qggkls*\/.css-1qggkls{outline:none;}.css-1qggkls p:first-of-type,.css-1qggkls .builder-paragraph:first-of-type{margin:0;}.css-1qggkls \u003e p,.css-1qggkls .builder-paragraph{color:inherit;line-height:inherit;-webkit-letter-spacing:inherit;-moz-letter-spacing:inherit;-ms-letter-spacing:inherit;letter-spacing:inherit;font-weight:inherit;font-size:inherit;text-align:inherit;font-family:inherit;}\/*end:1qggkls*\/ \/*start:ur9nhf*\/.css-ur9nhf.builder-block{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;position:relative;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;box-sizing:border-box;margin-top:20px;height:2px;background-color:rgba(221,221,221,1);}\/*end:ur9nhf*\/ \/*start:1mvsfya*\/.css-1mvsfya.builder-block{height:0;width:0;display:inline-block;opacity:0;overflow:hidden;pointer-events:none;}\/*end:1mvsfya*\/\u003c\/style\u003e\n\u003cdiv class=\"builder-component builder-component-fce05cc567b44bf5a38c469ad843e87c\" data-name=\"product-description\" data-source=\"Rendered by Builder.io\"\u003e\u003cdiv class=\"builder-content\" builder-content-id=\"fce05cc567b44bf5a38c469ad843e87c\" builder-model=\"product-description\"\u003e\u003cdiv data-builder-component=\"product-description\" data-builder-content-id=\"fce05cc567b44bf5a38c469ad843e87c\" data-builder-variation-id=\"fce05cc567b44bf5a38c469ad843e87c\"\u003e\n\u003cstyle data-emotion-css=\"h47494\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-blocks css-h47494\" builder-type=\"blocks\"\u003e\n\u003cstyle data-emotion-css=\"1t2m0n6\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-a38d2a740bf04ec2ac6740a031a0a20f builder-has-component css-1t2m0n6\" builder-id=\"builder-a38d2a740bf04ec2ac6740a031a0a20f\"\u003e\n\u003cstyle data-emotion-css=\"1840m1q\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-columns css-1840m1q\"\u003e\n\u003cstyle data-emotion-css=\"1ukkadj\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-column css-1ukkadj\"\u003e\u003cdiv class=\"builder-blocks builder-blocks-child css-h47494\" builder-type=\"blocks\"\u003e\n\u003cstyle data-emotion-css=\"hgfgng\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-78f1063421e844a58772a6254f4094de builder-has-component css-hgfgng\" builder-id=\"builder-78f1063421e844a58772a6254f4094de\"\u003e\n\u003cstyle data-emotion-css=\"1qggkls\"\u003e\u003c\/style\u003e\n\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003eThe KR Audio 274B rectifier tube is a high-end full-wave thermionic vacuum tube that sets the standard for exceptional performance and audiophile-grade sound quality. This meticulously crafted tube is designed to elevate your audio experience by providing a stable, regular voltage and superior current rectification, ensuring that your amplifier delivers the rich, detailed \u0026amp; Musical sound you demand. Ideal for use in tube amplifiers \u0026amp; preamplifiers, the KR Audio 274B is a versatile addition to any hi-fi setup.\u003c\/p\u003e\n\u003cp\u003eThe KR Audio 274B is the result of years of research and development, combining advanced engineering with the finest materials and filaments to create a rectifier tube that stands head and shoulders above the competition. Its superior design ensures long life and reliable operation, making it the perfect choice for discerning audiophiles who refuse to compromise on sound quality. At the heart of the KR Audio 274B's outstanding performance is its ability to deliver a stable, regular voltage to your amplifier's circuit. By providing a clean and consistent power supply, this tube allows your amplifier to operate at its full potential, reproducing music with unparalleled clarity, dynamics, and emotional impact.\u003c\/p\u003e\n\u003cp\u003eThe 274B's excellent current rectification capabilities ensure that your amplifier has the necessary power to handle even the most demanding musical passages with ease. This tube's superior rectification process minimizes voltage drops and reduces noise, resulting in a cleaner, more transparent sound that brings out the best in your favorite recordings. Available in variations such as the 5U4G rectifier vacuum tube, GE 5U4GA, and RCA 5U4GB, and produced by renowned manufacturers like Electro-Harmonix, Western Electric, Sophia Electric, Sylvania, and Takatsuki, this new production tube maintains the heritage of high-quality USA-made power tubes. We consider the KR Audio version one of the best on the market.\u003c\/p\u003e\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"ur9nhf\"\u003e\u003c\/style\u003e\n\u003cdiv class=\"builder-block builder-13c7f99af1594f23803e772997ef2365 css-ur9nhf\" builder-id=\"builder-13c7f99af1594f23803e772997ef2365\"\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-c2353908ee8b4c9f96d9133aa3ab9159 builder-has-component css-hgfgng\" builder-id=\"builder-c2353908ee8b4c9f96d9133aa3ab9159\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eKR Audio WARRANTY ON TUBES ONLY\u003c\/h3\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-b07acea0cb4241e1be9c06f5ec2685f9 builder-has-component css-hgfgng\" builder-id=\"builder-b07acea0cb4241e1be9c06f5ec2685f9\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003cp\u003ePlease take a moment to return your warranty registration form included with the tubes. Unregistered KR tubes will not be warranted. Customers must return the warranty registration when the tubes have been received. \u003c\/p\u003e\n\u003cp\u003eKR Audio Electronics will respect valid warranty claims. Incorrect claims or late warranty registration will void any guarantee. KR Audio Electronics will replace the tube provided the following conditions are met: \u003c\/p\u003e\n\u003col\u003e\n\u003cli\u003eThe tubes were used according to the technical data sheet enclosed with the KR tube. \u003c\/li\u003e\n\u003cli\u003eAbuse, accident or unauthorized use of the tube will be determined by KR Audio Electronics. \u003c\/li\u003e\n\u003cli\u003eAll tubes to be returned with the original factory box and warranty. \u003c\/li\u003e\n\u003cli\u003eTo obtain a replacement for a faulty tube, KR Audio Electronics reserves the right to obtain dealer or distributor authorization prior to shipping products pre-paid back to us. \u003c\/li\u003e\n\u003c\/ol\u003e\n\u003cp\u003eKR Audio Electronics gives a one-year warranty for your tube from the date of purchase. The purchase date should be written or stamped by the dealer or distributor on the day you buy the tube. Only expert technicians can change the work point of the tube. Improper use of the tube or incorrect application of the tube to a circuit cannot be covered by our warranty. \u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-c7d11dd9ae114a818dfd35ac3c7666a4 builder-has-component css-hgfgng\" builder-id=\"builder-c7d11dd9ae114a818dfd35ac3c7666a4\"\u003e\u003cspan class=\"builder-text css-1qggkls\"\u003e\u003ch3\u003eMoon Audio Tube Testing Process\u003c\/h3\u003e\n\u003cp\u003eOur high-end audio systems achieve sonic purity through the use of carefully selected NOS vacuum tubes. We take time to search for NOS tubes, understanding their unique potential for audio reproduction. Each tube is rigorously tested using legendary HICKOK 800K 600K Dynamic Mutual Conductance Tube Tester and TV7-A\/U Vacuum Tube Testers to measure critical parameters, including mutual conductance, emission, and gas levels. By precisely matching tubes based on these measurements, we deliver balanced, dynamic, and lifelike audio that elevates your listening experience to an art form.  \u003c\/p\u003e\u003c\/span\u003e\u003c\/div\u003e\n\u003cdiv class=\"builder-block builder-7526801cef4b485599db20a5a2cbad31 css-ur9nhf\" builder-id=\"builder-7526801cef4b485599db20a5a2cbad31\"\u003e\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"1mvsfya\"\u003e\u003c\/style\u003e\n\u003cimg src=\"https:\/\/cdn.builder.io\/api\/v1\/pixel?apiKey=48d1cdcd52ec4d289f1ef8c4f75da167\" aria-hidden=\"true\" alt=\"\" role=\"presentation\" width=\"0\" height=\"0\" class=\"builder-block builder-pixel-v9o5jdjw2n css-1mvsfya\" builder-id=\"builder-pixel-v9o5jdjw2n\"\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\u003c\/div\u003e\u003c\/builder-component\u003e\n\u003cscript async src=\"https:\/\/cdn.builder.io\/js\/webcomponents\"\u003e\u003c\/script\u003e","brand":"KR Audio","offers":[{"title":"Single ($675)","offer_id":49976888131898,"sku":"274b-KR-S","price":675.0,"currency_code":"USD","in_stock":true},{"title":"Matched Pair ($1350)","offer_id":49976888164666,"sku":"274b-KR-P","price":1350.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0834\/0245\/7402\/files\/KR-274B-KR-Audio-274B-01.jpg?v=1728669967"},{"product_id":"kr-audio-el34d-tube","title":"EL34D Tube","description":"\u003c!-- ***** Generated by Builder.io on Tue, 26 May 2026 19:55:56 GMT ***** --\u003e\n\u003cstyle class=\"builder-styles builder-api-styles\" type=\"text\/css\"\u003e\/*start:h47494*\/.css-h47494{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;-webkit-align-items:stretch;-webkit-box-align:stretch;-ms-flex-align:stretch;align-items:stretch;}\/*end:h47494*\/ \/*start:1rq6f32*\/.css-1rq6f32.builder-block{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;position:relative;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;box-sizing:border-box;margin-top:20px;height:auto;margin-left:200px;margin-right:200px;padding-bottom:30px;}@media only screen and (max-width:991px){.css-1rq6f32.builder-block{margin-left:20px;margin-right:20px;}}\/*end:1rq6f32*\/ \/*start:hgfgng*\/.css-hgfgng.builder-block{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;position:relative;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;box-sizing:border-box;margin-top:20px;line-height:normal;height:auto;}\/*end:hgfgng*\/ \/*start:1qggkls*\/.css-1qggkls{outline:none;}.css-1qggkls p:first-of-type,.css-1qggkls .builder-paragraph:first-of-type{margin:0;}.css-1qggkls \u003e p,.css-1qggkls .builder-paragraph{color:inherit;line-height:inherit;-webkit-letter-spacing:inherit;-moz-letter-spacing:inherit;-ms-letter-spacing:inherit;letter-spacing:inherit;font-weight:inherit;font-size:inherit;text-align:inherit;font-family:inherit;}\/*end:1qggkls*\/ \/*start:1n465md*\/.css-1n465md.builder-block{height:0;width:0;display:block;opacity:0;overflow:hidden;pointer-events:none;}\/*end:1n465md*\/\u003c\/style\u003e\n\u003cstyle data-emotion-css=\"h47494\"\u003e\u003c\/style\u003e\n\u003cstyle data-emotion-css=\"1rq6f32\"\u003e\u003c\/style\u003e\n\u003cstyle data-emotion-css=\"hgfgng\"\u003e\u003c\/style\u003e\n\u003cstyle data-emotion-css=\"1qggkls\"\u003e\u003c\/style\u003e\n\u003cdiv data-source=\"Rendered by Builder.io\" data-name=\"product-description\" class=\"builder-component builder-component-8ac5cdbc46694aff9ba17bea89f14d8a\"\u003e\n\u003cdiv class=\"builder-content\"\u003e\n\u003cdiv data-builder-variation-id=\"8ac5cdbc46694aff9ba17bea89f14d8a\" data-builder-content-id=\"8ac5cdbc46694aff9ba17bea89f14d8a\" data-builder-component=\"product-description\"\u003e\n\u003cdiv class=\"builder-blocks css-h47494\"\u003e\n\u003cdiv class=\"builder-block builder-c0d0cbfeb4c44f3a81a625e003511587 css-1rq6f32\"\u003e\n\u003cdiv class=\"builder-block builder-ea8be73a8a1045a689e1a54e2aee7bb8 builder-has-component css-hgfgng\"\u003e\n\u003cp\u003eThe KR Audio EL34D is an ultra-premium, handcrafted vacuum tube engineered in the Czech Republic, designed explicitly for audiophiles who demand uncompromising sonic luxury. Built with an exceptionally robust glass envelope and heavy-duty internal components, this tube delivers the classic EL34 signature tone elevated to a reference-grade performance level. Sellers can confidently highlight its breathtaking audio profile, which features an incredibly liquid, detailed midrange, velvety smooth highs, and a highly articulated, quick low-end response. It is a highly coveted upgrade for high-end stereo systems, offering a massive leap in soundstage depth, instrument separation, and overall structural durability compared to standard mass-produced alternatives.\u003c\/p\u003e\n\u003cp\u003eTechnically, the KR Audio EL34D offers seamless integration across diverse amplifier topologies. It is fully compatible with EL34 straight pentode design circuit amplifiers, as well as versatile toggle design amplifiers that feature user-selectable switches between ultra-linear and pentode modes. For listeners seeking the ultimate in sonic purity, utilizing a triode-only connection or selecting the triode mode on switchable circuits yields the best possible linearity, drastically reducing distortion and delivering unmatched musical accuracy. Whichever configuration is used, implementing these drop-in upgrades provides listeners with an enhanced, deeply immersive musical experience marked by expanded dynamic headroom and exceptional acoustic realism.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cstyle data-emotion-css=\"1n465md\"\u003e\u003c\/style\u003e\n\u003cdiv data-source=\"Rendered by Builder.io\" data-name=\"product-description\" class=\"builder-component builder-component-8ac5cdbc46694aff9ba17bea89f14d8a\"\u003e\n\u003cdiv class=\"builder-content\"\u003e\n\u003cdiv data-builder-variation-id=\"8ac5cdbc46694aff9ba17bea89f14d8a\" data-builder-content-id=\"8ac5cdbc46694aff9ba17bea89f14d8a\" data-builder-component=\"product-description\"\u003e\n\u003cdiv class=\"builder-blocks css-h47494\"\u003e\u003cimg class=\"builder-block builder-pixel-ias9mqjezi css-1n465md\" height=\"0\" width=\"0\" role=\"presentation\" alt=\"\" aria-hidden=\"true\" src=\"https:\/\/cdn.builder.io\/api\/v1\/pixel?apiKey=48d1cdcd52ec4d289f1ef8c4f75da167\"\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cp\u003e \u003c\/p\u003e","brand":"KR Audio","offers":[{"title":"Pair ($750.00)","offer_id":53532895019322,"sku":"EL34D-Pair","price":750.0,"currency_code":"USD","in_stock":true},{"title":"Quad ($1500)","offer_id":53532895052090,"sku":"EL34D-Quad","price":1500.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0834\/0245\/7402\/files\/EL34DPair.jpg?v=1780514602"}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0834\/0245\/7402\/collections\/download_20_282_29_1715947570__19560_25f323f3-4c79-4c89-b446-588fc8a0adc4.png?v=1723059239","url":"https:\/\/www.moon-audio.pro\/collections\/brands-kr-audio.oembed","provider":"Moon Audio","version":"1.0","type":"link"}