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6L6 famility to KT88 and 2A3.. Re: Actually, I did not say that

Posted by wlee (A) on June 24, 2006 at 23:10:59

In Reply to: Actually, I did not say that posted by j rodney on June 24, 2006 at 22:13:34:

For the good part of last 1 year, I did try from 6L6GC EH/JJ, KT66 GEC clear glass brown base/Sovtek, EL37 smoked small bottle, 7581A, EL34 (EH/JJ/Matshusita/old Tesla_Brimar, Old Svet, philips metal based),6CA7 EH, KT77 GEC and JJ, old and new TS 6550, KT88 GEC 3 and top getters and Sino, Ei KT90, and finally Sino EL156.... Biasing to sweet spot which tend to be 24Ma for the 6L6Gc to 45 Ma for Ei KT90.
I used Hadley 601, Fisher 100, and an Eastern Electric EL34 amp modified to have just EF86 driving the output tubes in Long Tailed Push Pull configuration with the cathode resistor ranging from 300 Ohms to 600 Ohms, un-bi-passed. For speakers mainly I used Altec 755A in 1 ch, the other ch various speakers though all not as nice sounding as the 755A.
Roughly nice tubes to listen to are Ei KT90, GEC KT88, TS 6550, Sino EL156, JJ KT77, and perhaps Tesla EL34 and 7581A. Ok tubes are matsushita EL34, JJ and EH 6L6GC, GEC KT77, EL37. The OK tubes req more works to make them good sounding. Perhaps as they are more difficult to drive. the rest are not so nice sounding, meaning a bit hard sounding.
I find the sound of those tubes depends a lot on the G2 voltage. SO the not so good souning tubes above, if given better g2 supply, along the line of Jeff Dr Low Mu research, but adjustable to give the tube sweet spot working condition, that migh solve the problem. mine is fixed to the same as the B= which is around 420V. My Eastern Electric PT secondary has about 40 Ohms...

In general, I find that I like the penthode driver better then the triode, for sweeter sound. Triode front end has cleaner sound, but could be boring after a while. For Triode I like 12AX7/TS ECC803S best, but I just tried the JJ ECC81 gold pin and find the sound to be quite nice too, unlike the rest of the 12AT7 which is harder sounding.
How is you guys' amp working condition?
So far I have good result with JJ 2A3 driven by TS ECC803S, but it could sound a bit boring in really long term listening, meaning playing non stop for more then 48 hours. So I might try some penthode. Advise I got is C3M, but as I don't want to change the tubes socket, I may try 12BY7 first... BTW for SE it seemed the sweet spot is at the highest or near highest bias.

Tks and bets rgds

William Lee

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