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  #331  
Old 11-20-2018, 04:27 PM
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W9TR W9TR is offline
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Hi Dan,
I'm testing the tubes in a Stark 9-66 tester. It's a Canadian Hickock. I am losing a little bit of the awesome dynamics. Not much, but enough to notice when I put in new tubes. The Transconductance tests less than 75% of new, around 3500 uMho. Gain and emissions seem ok, not much change there if any. I don't understand the mechanism that is causing the transconductance to drop when the gain and emissions are still good.
Tom
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  #332  
Old 11-20-2018, 04:59 PM
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jdandy jdandy is offline
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Quote:
Originally Posted by W9TR View Post
Hi Dan,
I'm testing the tubes in a Stark 9-66 tester. It's a Canadian Hickock. I am losing a little bit of the awesome dynamics. Not much, but enough to notice when I put in new tubes. The Transconductance tests less than 75% of new, around 3500 uMho. Gain and emissions seem ok, not much change there if any. I don't understand the mechanism that is causing the transconductance to drop when the gain and emissions are still good.
Tom
Tom.......Even at 75% transconductance the 12AT7's should still be fully operational. My Siemen's ECC801S tubes tested just over 75% transconductance at 2000 hours when compared to brand new tubes. I don't notice any loss of dynamic range, but then I am not rolling in brand new tubes with the intent of making back to back comparison.

I have four Gold Lion gold pin 12AT7's that have about 50 hours on them, four new Tung-Sol 12AT7's, and four new Siemens E81CC tubes with the three mica support. I should probably order a new quad of the Siemens ECC801S tubes while TubeMonger still has them. They sound excellent in the MC2301 amps.
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STUDIO - McIntosh C1000C/P, MC2301 (2), MR88, Aurender N10, Esoteric K-01X, Shunyata Sigma spdif digital cable, Sonos Connect, PurePower 2000, Stillpoints, Furutech Flux 50, Michell Gyro SE, Michell HR Power Supply, SME 309, Ortofon Cadenza Black, Wireworld, Sonus faber Amati Anniversario
LIVING ROOM - McIntosh C2300, MC75 (2), MR85, Magnum Dynalab 205, Simaudio MOON Neo 260D-T, Schiit Audio Yggdrasil, Aurender N100H, Shunyata Sigma USB cable, Micro Seiki DD40, Ortofon Cadenza Blue, Nakamichi BX-300, Sony 60ES DAT, PS Audio P10, Furutech Flux 50, Sonos Connect, Stillpoints, Wireworld, Kimber, PMC EB1i, JL Audio f113
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