{"product_id":"6c6-ck108-nu-national-union-nos-nib-grafite-glass-matched-pair-tubes-made-in-usa","title":"6C6 ( CK108 ) NU National Union NOS NIB Graphite Glass Matched Pair Tubes Made in USA","description":"\u003cp\u003e\u003cmeta charset=\"utf-8\"\u003e \u003cstrong\u003e6C6 ( CK108 ) NU National Union NOS NIB Graphite Glass Matched Pair Tubes Made in USA\u003c\/strong\u003e\u003cbr\u003e\u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eDescription:\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp data-end=\"818\" data-start=\"376\"\u003eA true expression of the American school of construction, these \u003cstrong data-end=\"481\" data-start=\"444\"\u003e6C6s (military designation CK108)\u003c\/strong\u003e produced by \u003cstrong data-end=\"512\" data-start=\"494\"\u003eNational Union\u003c\/strong\u003e are distinguished by their characteristic graphite glass, designed to reduce internal light interference and improve thermal stability.\u003cbr data-end=\"658\" data-start=\"655\"\u003e\u003cstrong data-end=\"679\" data-start=\"668\"\u003eNOS NIB\u003c\/strong\u003e examples, selected and supplied in matched pairs, ideal for both high-end audio applications and for philological restorations of vintage equipment.\u003c\/p\u003e\n\u003ch3 data-end=\"877\" data-start=\"825\"\u003eTimbre characteristics and sound description\u003c\/h3\u003e\n\u003cp data-end=\"1042\" data-start=\"879\"\u003e\u003cstrong data-end=\"889\" data-start=\"879\"\u003eBass:\u003c\/strong\u003e \u003cbr data-end=\"892\" data-start=\"889\"\u003eClean and compact, with a dry and well-controlled timbre. The low end is never intrusive, but integrates seamlessly into the musical fabric.\u003c\/p\u003e\n\u003cp data-end=\"1213\" data-start=\"1044\"\u003e\u003cstrong data-end=\"1053\" data-start=\"1044\"\u003eMedium:\u003c\/strong\u003e\u003cbr data-end=\"1056\" data-start=\"1053\"\u003eRefined and natural, with excellent reproduction of vocals and acoustic instruments. The harmonics are rich and coherent, giving a sense of realistic presence.\u003c\/p\u003e\n\u003cp data-end=\"1365\" data-start=\"1215\"\u003e\u003cstrong data-end=\"1224\" data-start=\"1215\"\u003eHighs:\u003c\/strong\u003e\u003cbr data-end=\"1227\" data-start=\"1224\"\u003eExtended yet silky, with controlled brightness and no harshness. The high-frequency response is pleasant even over long listening sessions.\u003c\/p\u003e\n\u003cp data-end=\"1477\" data-start=\"1367\"\u003e\u003cstrong data-end=\"1380\" data-start=\"1367\"\u003eDynamics:\u003c\/strong\u003e\u003cbr data-end=\"1383\" data-start=\"1380\"\u003eResponsive and fluid, capable of rendering micro and macro details without perceptible compression.\u003c\/p\u003e\n\u003cp data-end=\"1634\" data-start=\"1479\"\u003e\u003cstrong data-end=\"1494\" data-start=\"1479\"\u003eSoundstage:\u003c\/strong\u003e\u003cbr data-end=\"1497\" data-start=\"1494\"\u003eWell-focused scene, with stable positioning of the sources and a realism that enhances both mono and stereo recordings.\u003c\/p\u003e\n\u003ch3 data-end=\"1676\" data-start=\"1641\"\u003e🎧 Use in Hi-Fi Amplifiers\u003c\/h3\u003e\n\u003cp data-end=\"1906\" data-start=\"1677\"\u003ePerfect for vintage amplifiers and preamps requiring 6C6, where the graphite glass contributes to a clean, interference-free sound. Ideal for high-efficiency systems and those seeking natural tonal quality.\u003c\/p\u003e\n\u003ch3 data-end=\"1945\" data-start=\"1908\"\u003e🎸 Use in Music Applications\u003c\/h3\u003e\n\u003cp data-end=\"2108\" data-start=\"1946\"\u003eSuitable for vintage radios and instrument amplifiers, they deliver a warm, defined and harmonically rich sound, ideal for authentic vintage contexts.\u003c\/p\u003e\n\u003ch3 data-end=\"2147\" data-start=\"2110\"\u003e🎯 Note for audiophiles and technicians\u003c\/h3\u003e\n\u003cp data-end=\"2413\" data-start=\"2148\"\u003eThe graphite-glass \u003cstrong data-end=\"2173\" data-start=\"2151\"\u003eNational Union 6C6s\u003c\/strong\u003e are a particularly stable and quiet version. Matched pairing ensures consistent and reliable performance, making them an excellent option for high-end restorations or specialized hi-fi projects.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch3\u003e\u003cstrong\u003eTest Results:\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eTested with \u003cstrong\u003eAMPLITREX AT-1000\u003c\/strong\u003e Tube tester:\u003cbr\u003eMeasurements taken \u003cstrong\u003eafter 10 minutes\u003c\/strong\u003e of preheating.\u003cbr\u003e\u003cmeta charset=\"utf-8\"\u003e \u003cstrong\u003eTest Conditions:\u003c\/strong\u003e \u003cspan\u003eVa = 250V ; Vg2 = 100V ; Vg = 3V\u003c\/span\u003e \u003cbr\u003e\u003cstrong\u003eAVERAGE 100%:\u003c\/strong\u003e Gm = 1200 ; Ia = 2 mA\u003cbr\u003e\u003cstrong\u003eTest Result:\u003c\/strong\u003e VERY STRONG\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eValve 1: Gm = 1000 ; Ia = 1.3 mA\u003cbr\u003e\u003c\/li\u003e\n\u003cli\u003e\u003cmeta charset=\"utf-8\"\u003e Valve 2: Gm = 1100 ; Ia = 1.5 mA\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cdiv\u003e\u003cstrong\u003eAdditional Tests Performed:\u003c\/strong\u003e\u003c\/div\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cspan\u003e\u003cstrong\u003eMicrophonics:\u003c\/strong\u003e Low. 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 \u003cspan\u003eNOS - NIB - New Old Stock, New In Box - Tested and working - Supplied in original box.\u003c\/span\u003e\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:\u003cspan\u003e\u0026nbsp;\u003c\/span\u003e\u003c\/strong\u003eMR IR - undecipherable\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cmeta charset=\"utf-8\"\u003e\u003ca rel=\"noopener\" title=\"Why our tubes are different – the VTT protocol that improves sound, reliability and durability\" href=\"https:\/\/vacuumtubestreasures.com\/blogs\/notizie\/perche-le-nostre-valvole-sono-diverse\" target=\"_blank\"\u003e\u003cstrong\u003eFind out why our valves are different →\u003c\/strong\u003e\u003c\/a\u003e\u003c\/p\u003e","brand":"NATIONAL UNION","offers":[{"title":"Default Title","offer_id":55225005506908,"sku":"03045S","price":47.9,"currency_code":"EUR","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0616\/3775\/5127\/files\/1_3b6c7431-e391-4f38-b799-338d8bef0fc2.jpg?v=1754991606","url":"https:\/\/vacuumtubestreasures.com\/en-lv\/products\/6c6-ck108-nu-national-union-nos-nib-grafite-glass-matched-pair-tubes-made-in-usa","provider":"Vacuum Tubes Treasures","version":"1.0","type":"link"}