{"product_id":"5u4gb-5as4a-rca-black-plates-tube-top-side-square-getter-rectifier-made-in-usa-56","title":"5U4GB 5AS4A RCA NOS Black Plates Tube Top Side Square Getter Rectifier Made in USA '56","description":"\u003cp\u003e\u003cstrong\u003e5U4GB 5AS4A RCA NOS Black Plates Tube Top Side Square Getter Rectifier Made in USA '56\u003c\/strong\u003e\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eDescription:\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThe \u003cstrong\u003eRCA 5U4GB \/ 5AS4A\u003c\/strong\u003e , in this 1956 version with \u003cstrong\u003eblack plates\u003c\/strong\u003e , \u003cstrong\u003esquare getter\u003c\/strong\u003e in the \u003cstrong\u003etop and side\u003c\/strong\u003e position, represents one of the most stable and balanced variants of the classic RCA rectifier, fully compatible with high-end audio use.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eBass\u003c\/strong\u003e : precise and controlled. The bass extension is solid but never intrusive, with a tight and coherent response even under complex loads. The bass structure contributes to rhythmic stability without introducing inaccuracies or bloat.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eMids\u003c\/strong\u003e : Clean and well-articulated. The midrange is presented in a neutral and uncluttered manner, with particular attention to the tonal coherence of vocals and acoustic instruments. There is no tendency to harden or thin out, which favors the overall balance.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHighs\u003c\/strong\u003e : Sober and natural. The high range is well-integrated, without excessive brightness or obvious grain. Detail is present but never invasive, leaving room for musicality and reducing listening fatigue even during prolonged listening.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDynamics\u003c\/strong\u003e : linear and stable. Transient response is smooth, with predictable and well-balanced behavior even under variable load conditions. No \"pumping\" effect, just an organic dynamic progression.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eSoundstage\u003c\/strong\u003e : Coherent and well-structured. The stereo image is clear and stable, with good definition of the soundstage. The soundstage develops naturally in depth and width, without forced expansion.\u003c\/p\u003e\n\u003cp\u003e🎧 \u003cstrong\u003eUse in Headphone Amplifiers and Hi-Fi Driver Stages\u003c\/strong\u003e\u003cbr\u003ePerfect for tube DACs and reference preamps, this tube offers clean delivery and extremely low noise. Its tonal balance and transparency are ideal for enhancing microdynamics and depth with demanding headphones like \u003cstrong\u003ethe Focal Utopia\u003c\/strong\u003e , \u003cstrong\u003eSennheiser HD800S\u003c\/strong\u003e , and \u003cstrong\u003eZMF Atrium\u003c\/strong\u003e .\u003c\/p\u003e\n\u003cp\u003e🎸 \u003cstrong\u003eUse in Guitar and Bass Amplifiers\u003c\/strong\u003e\u003cbr\u003eOften installed in \u003cstrong\u003evintage Fender\u003c\/strong\u003e amplifiers (such as the Twin Reverb, Bandmaster and Showman) and their boutique derivatives, this rectifier provides \u003cstrong\u003enatural progressive compression\u003c\/strong\u003e , with a \u003cstrong\u003econtrolled musical sag\u003c\/strong\u003e , perfect for cleans, blues and the dynamic crunch typical of the 60s American sound.\u003c\/p\u003e\n\u003cp\u003e🎯 \u003cstrong\u003eNote for audiophiles and technicians\u003c\/strong\u003e\u003cbr\u003eA technically robust and musically neutral tube, ideal for those looking for a stable, silent and reliable electric base.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch3\u003e\u003cstrong\u003eTest Results\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eTubes Tested\u003c\/strong\u003e on \u003cstrong\u003eFunke W19\u003c\/strong\u003e Tube Tester:\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eVoltage Test:\u003c\/strong\u003e Va = 100V, Vf = 5V \u003cstrong\u003e\u003cbr\u003eGood from:\u003c\/strong\u003e Ia = 78 mA \u003cstrong\u003e\u003cbr\u003eAverage 100%:\u003c\/strong\u003e Ia = 120 mA \u003cstrong\u003e\u003cbr\u003eTEST RESULT:\u003c\/strong\u003e VERY STRONG\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eValve\u003c\/strong\u003e :\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eSection 1\u003c\/strong\u003e : Ia = 140 mA\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eSection 2\u003c\/strong\u003e : Ia = 130 mA\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cdiv\u003e\u003cstrong\u003e\u003c\/strong\u003e\u003cbr\u003e\u003c\/div\u003e\n\u003cdiv\u003e\u003cstrong\u003eAdditional Tests Performed:\u003c\/strong\u003e\u003c\/div\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eOperation:\u003c\/strong\u003e Stable valve, quiet in operation, and suitable for regular and controlled power supply. Tested with a Funke W19 tester.\u003c\/li\u003e\n\u003cli\u003e\u003cspan\u003e\u003cstrong\u003eOutput Quality:\u003c\/strong\u003e Excellent – Very strong and stable output, no fluctuations.\u003c\/span\u003e\u003c\/li\u003e\n\u003cli\u003e\u003cspan\u003e\u003cstrong\u003eShort circuits and GAS:\u003c\/strong\u003e Absent.\u003c\/span\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr\u003e\n\u003ch3\u003e\u003cstrong\u003eConditions:\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eCondition:\u003c\/strong\u003e NOS - New Old Stock - Tested and working - Supplied in our custom box for optimal protection.\u003cstrong\u003e\u003cbr\u003e\u003c\/strong\u003e\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eFunctionality:\u003c\/strong\u003e Fully functional.\u003cstrong\u003e\u003cbr\u003e\u003c\/strong\u003e\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eCosmetic condition:\u003c\/strong\u003e \u003cspan\u003eExcellent – Excellently preserved lettering, minimal signs of wear. See photos for details.\u003c\/span\u003e\u003cstrong\u003e\u003cbr\u003e\u003c\/strong\u003e\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eManufacturing Code:\u003c\/strong\u003e 56-43 → RMA\/EIA Open Date Code → manufactured week 43 of 1956\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cmeta charset=\"utf-8\"\u003e \u003ca href=\"https:\/\/vacuumtubestreasures.com\/blogs\/notizie\/perche-le-nostre-valvole-sono-diverse\" title=\"Why our tubes are different – the VTT protocol that improves sound, reliability and durability\" rel=\"noopener\" target=\"_blank\"\u003e\u003cstrong\u003eFind out why our valves are different →\u003c\/strong\u003e\u003c\/a\u003e\u003c\/p\u003e","brand":"RCA","offers":[{"title":"Default Title","offer_id":56567919182172,"sku":"03379","price":7800.0,"currency_code":"ALL","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0616\/3775\/5127\/files\/1_8dc8e58c-50b3-40c3-943e-c56c645b5249.jpg?v=1769428190","url":"https:\/\/vacuumtubestreasures.com\/en-al\/products\/5u4gb-5as4a-rca-black-plates-tube-top-side-square-getter-rectifier-made-in-usa-56","provider":"Vacuum Tubes Treasures","version":"1.0","type":"link"}