{"product_id":"6550-ge-by-tung-sol-type-2-4th-generation-amplitrex-matched-quad-made-in-usa","title":"6550 GE by TUNG-SOL Type 2 – 4th Generation - AMPLITREX Matched Quad - Made in USA","description":"\u003cp\u003e\u003cmeta charset=\"utf-8\"\u003e\u003cstrong\u003e6550 GE by TUNG-SOL Type 2 - 4th Generation Gray Plates Triple Halo Getter Three Holes Matched Quad Tubes MADE IN USA\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cspan style=\"text-decoration: underline;\"\u003e\u003cstrong\u003eImportant note on conditions\u003c\/strong\u003e\u003c\/span\u003e\u003cbr\u003eOne of the four valves has the central plastic key glued on (mechanical defect visible in the photograph).\u003cbr\u003eThe flash getter appears aesthetically irregular, as visible in the photo.\u003cbr\u003eThere is no internal gas and these aspects do not affect electrical operation, safety or sound performance in any way.\u003cbr\u003eThe quartet is fully operational and stable.\u003c\/p\u003e\n\u003cp\u003eThe price transparently takes into account the conditions described above, despite the presence of VERY STRONG electrical tests and full functionality of the set.\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eDescription:\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp data-start=\"386\" data-end=\"909\"\u003eThis \u003cstrong data-start=\"393\" data-end=\"437\"\u003ematched quartet of 6550 GE by Tung-Sol\u003c\/strong\u003e , Made in USA, belongs to the \u003cstrong data-start=\"468\" data-end=\"495\"\u003eType 2 – 4th generation\u003c\/strong\u003e , one of the most mature and musically balanced versions of the historic American 6550.\u003cbr data-start=\"583\" data-end=\"586\"\u003eThe construction with \u003cstrong data-start=\"605\" data-end=\"620\"\u003egray plates\u003c\/strong\u003e , \u003cstrong data-start=\"622\" data-end=\"644\"\u003etriple halo getter\u003c\/strong\u003e and \u003cstrong data-start=\"647\" data-end=\"675\"\u003ethree ventilation holes\u003c\/strong\u003e reflects a production phase oriented towards maximum electrical stability, controlled thermal dissipation and long operational reliability, maintaining intact the authoritative sound character typical of the best vintage 6550s.\u003c\/p\u003e\n\u003cp data-start=\"911\" data-end=\"1259\"\u003eThe set was \u003cstrong data-start=\"926\" data-end=\"959\"\u003eselected as Matched Quad\u003c\/strong\u003e and tested with professional equipment, resulting \u003cstrong data-start=\"1015\" data-end=\"1030\"\u003eVERY STRONG\u003c\/strong\u003e , with homogeneous behavior and consistent response on all tubes.\u003cbr data-start=\"1099\" data-end=\"1102\"\u003eThis is a quartet designed for medium-high and high-end amplifiers, where balance, control and solidity of tone are fundamental requirements.\u003c\/p\u003e\n\u003chr data-start=\"1261\" data-end=\"1264\"\u003e\n\u003ch3 data-start=\"1266\" data-end=\"1286\"\u003eSound Character\u003c\/h3\u003e\n\u003cp data-start=\"1288\" data-end=\"1487\"\u003e\u003cstrong data-start=\"1288\" data-end=\"1297\"\u003eBass\u003c\/strong\u003e\u003cbr data-start=\"1297\" data-end=\"1300\"\u003eDeep, compact, and perfectly controlled. The low end is authoritative but never intrusive, with excellent articulation and the ability to handle complex loads without losing definition.\u003c\/p\u003e\n\u003cp data-start=\"1489\" data-end=\"1677\"\u003e\u003cstrong data-start=\"1489\" data-end=\"1497\"\u003eMedium\u003c\/strong\u003e\u003cbr data-start=\"1497\" data-end=\"1500\"\u003eBalanced, full, and natural. The vocals are solid and well-focused, with a rich yet composed harmonic texture. They perform excellently on jazz, classic rock, and orchestral repertoire.\u003c\/p\u003e\n\u003cp data-start=\"1679\" data-end=\"1866\"\u003e\u003cstrong data-start=\"1679\" data-end=\"1687\"\u003eHigh\u003c\/strong\u003e \u003cbr data-start=\"1687\" data-end=\"1690\"\u003eClean, extended, and uncluttered. The highs are present but never aggressive, with a balance that favors prolonged listening and delivers air and detail without fatiguing.\u003c\/p\u003e\n\u003cp data-start=\"1868\" data-end=\"2017\"\u003e\u003cstrong data-start=\"1868\" data-end=\"1880\"\u003eDynamics\u003c\/strong\u003e\u003cbr data-start=\"1880\" data-end=\"1883\"\u003eConvincing and stable. Transient response is prompt yet controlled, with a sense of always-available power reserves.\u003c\/p\u003e\n\u003cp data-start=\"2019\" data-end=\"2175\"\u003e\u003cstrong data-start=\"2019\" data-end=\"2033\"\u003eSoundstage\u003c\/strong\u003e\u003cbr data-start=\"2033\" data-end=\"2036\"\u003eWide and well-structured, with a solid and credible soundstage. Excellent separation of levels and stable imaging even at high volumes.\u003c\/p\u003e\n\u003chr data-start=\"2177\" data-end=\"2180\"\u003e\n\u003ch3 data-start=\"2182\" data-end=\"2215\"\u003e🎧 Use in Hi-Fi Amplifiers\u003c\/h3\u003e\n\u003cp data-start=\"2216\" data-end=\"2227\"\u003eIdeal for:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli data-start=\"2230\" data-end=\"2262\"\u003e6550 push-pull amplifiers\u003c\/li\u003e\n\u003cli data-start=\"2265\" data-end=\"2305\"\u003efinal and integrated courses in American schools\u003c\/li\u003e\n\u003cli data-start=\"2308\" data-end=\"2383\"\u003esystems that require \u003cstrong data-start=\"2331\" data-end=\"2371\"\u003ebalance, control and reliability\u003c\/strong\u003e over time\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-start=\"2385\" data-end=\"2525\"\u003eAn excellent choice for those who want the classic 6550 sound in a more modern and balanced version than the very first generations.\u003c\/p\u003e\n\u003chr data-start=\"2527\" data-end=\"2530\"\u003e\n\u003ch3 data-start=\"2532\" data-end=\"2567\"\u003e🎸 Use in Music Applications\u003c\/h3\u003e\n\u003cp data-start=\"2568\" data-end=\"2583\"\u003eAppreciated for:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli data-start=\"2586\" data-end=\"2638\"\u003ehigh-powered bass and guitar amplifiers\u003c\/li\u003e\n\u003cli data-start=\"2641\" data-end=\"2732\"\u003eprofessional applications where stability, headroom and predictable response are required\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-start=\"2734\" data-end=\"2825\"\u003eThey offer a solid, defined and resistant sound even under demanding conditions of use.\u003c\/p\u003e\n\u003chr data-start=\"2827\" data-end=\"2830\"\u003e\n\u003ch3 data-start=\"2832\" data-end=\"2869\"\u003e🎯 Note for audiophiles and technicians\u003c\/h3\u003e\n\u003cp data-start=\"2870\" data-end=\"2953\"\u003eThis \u003cstrong data-start=\"2877\" data-end=\"2940\"\u003eMatched Quad of 6550 GE by Tung-Sol Type 2 – 4th Generation\u003c\/strong\u003e represents:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli data-start=\"2956\" data-end=\"3033\"\u003eone of the most reliable and musically balanced versions of the 6550 USA\u003c\/li\u003e\n\u003cli data-start=\"3036\" data-end=\"3094\"\u003eRobust construction with triple halo getters and gray plates\u003c\/li\u003e\n\u003cli data-start=\"3097\" data-end=\"3125\"\u003eaccurate matched selection\u003c\/li\u003e\n\u003cli data-start=\"3128\" data-end=\"3146\"\u003eVERY STRONG test\u003c\/li\u003e\n\u003cli data-start=\"3149\" data-end=\"3231\"\u003eexcellent compromise between \u003cstrong data-start=\"3176\" data-end=\"3231\"\u003esound performance, durability and collectible value\u003c\/strong\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp data-start=\"3233\" data-end=\"3388\" data-is-last-node=\"\" data-is-only-node=\"\"\u003eAn ideal quartet for those looking for \u003cstrong data-start=\"3267\" data-end=\"3360\"\u003ereal performance, tonal coherence and the authentic character of the great American 6550s\u003c\/strong\u003e , without unnecessary compromises.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch3\u003e\u003cstrong\u003eTest Results:\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eTested on \u003cstrong\u003eAMPLITREX AT-1000\u003c\/strong\u003e Tube tester: \u003cbr\u003e\u003cstrong\u003eTest Conditions:\u003c\/strong\u003e Va = 450V ; Vg2 = 300V ; Vg = -30V\u003cbr\u003eMeasurements are taken after 10 minutes of preheating the tubes.\u003cbr\u003e\u003cstrong\u003e100% average:\u003c\/strong\u003e Gm = 6.50 ; Ia = 50 mA\u003cbr\u003e\u003cstrong\u003eTEST RESULT:\u003c\/strong\u003e VERY STRONG\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eValve 1:\u003c\/strong\u003e Gm = 6.50 ; Ia = 56 mA\u003cbr\u003e\u003cstrong\u003eValve 2:\u003c\/strong\u003e Gm = 5.81 ; Ia = 54 mA\u003cbr\u003e\u003cstrong\u003eValve 3:\u003c\/strong\u003e Gm = 6.15 ; Ia = 54 mA\u003cbr\u003e\u003cstrong\u003eValve 4:\u003c\/strong\u003e Gm = 6.10 ; Ia = 47 mA\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdditional Tests Performed:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cspan\u003e\u003cstrong\u003eMicrophonics:\u003c\/strong\u003e\u003cmeta charset=\"utf-8\"\u003e Standard. Tested and approved for use in hi-fi and guitar amplifiers.\u003c\/span\u003e\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 Vintage tubes - Tested and in perfect working order. Shipped 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\u003eAesthetic condition:\u003c\/strong\u003e Very good – Clearly legible writing with slight signs of aging.\u003cmeta charset=\"utf-8\"\u003e One of the four valves has the central plastic key glued on (mechanical defect visible in the photograph).\u003cbr data-end=\"635\" data-start=\"632\"\u003eThis intervention does not affect the electrical operation, safety, or sound performance of the valve in any way, which remains fully operational and stable. See photos for details.\u003cstrong\u003e\u003cbr\u003e\u003c\/strong\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eManufacturing Code:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eNC → two-letter code → production October 1970\u003c\/li\u003e\n\u003cli\u003e\u003cmeta charset=\"utf-8\"\u003e MZ → two-letter code → production September 1969\u003c\/li\u003e\n\u003cli\u003e\u003cmeta charset=\"utf-8\"\u003e IC → two-letter code → production May 1970\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\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":"GE","offers":[{"title":"Default Title","offer_id":56498939232604,"sku":"03369","price":929.0,"currency_code":"EUR","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0616\/3775\/5127\/files\/1_768c5087-f7e3-419f-b060-cc4e6bb9ef4f.jpg?v=1768825894","url":"https:\/\/vacuumtubestreasures.com\/en-hr\/products\/6550-ge-by-tung-sol-type-2-4th-generation-amplitrex-matched-quad-made-in-usa","provider":"Vacuum Tubes Treasures","version":"1.0","type":"link"}