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In Reply to: no more nos 6922s Anyone going back to transistors? posted by yoyo on August 12, 2002 at 09:32:37:
For linestages and drivers the 6CG7/6FQ7 plug in and seem to work very well. In a circuit where plate resistance and gain are critical there is the old/new 6N11P. The 6N11P is much closer to a 6922 than the 6N1P is. In fact the 6N1P is closer to a 6FQ7 than it is to a 6922.
I gave up on most NOS 6DJ8 tubes a decade ago. My preamp then either eat them up, or they became microphonic very quickly. The original Russian 6922 from the 70's to mid 80's worked better.
Luck was with me once and I purchased a supply of NOS Amperex 6DJ8/6922 tubes, about 40 total. Some were BB, some were US manufacture HP, some were PDQ with gold pins. All were great sounding, but the problems with microphonics drove me back to the lowly Russians.
George
Follow Ups:
I'm no expert, but I do know a thing or two, and this sounds like a typo.... Please, someone back me up, correct me, elaborate on this, whatever it takes to shut me up :)
While they're not anywhere near being equivalent tubes, the 6CG7 can sometimes be used in place of a 6922, provided the circuit's designed to handle the extra load, and you don't mind the reduced gain. This is highly circuit dependent, but can give favorable results under the right conditions. Same can be said for some of the lesser known Russian tubes.
> > Same can be said for some of the lesser known Russian tubes. < <The 6N1P is the type most often mentioned. The single biggest issue with subbing a 6FQ7 or 6N1P for a 6922 is heater current draw. The 6922 draws 300 mA., while both the 6N1P and the 6FQ7 draw 600 mA. Unless it is absolutely certain that the power transformer heater winding can tolerate the added demand, these substitutions should not be made
Eli D.
but I think the pinout is the same. The 6CG7 is a lower gain, lower transconductance tube. 6DJ8's have very diferent grid construction and this probably contributes to some of the performance diffferences. If you get a Triode Electronics input board for ST70 it can be configured fo 6CG7 of 12BH7/AU7 etc. I think you could plug in a 6DJ8 but this service would exceed its voltage ratings( well maybe, 450 V total, take away 100 V across the cathode resistor, take away equal 1100 v for plate load and we're looking at 250 V on the plates, probably less due to droping resistor to its supply, maybe 200 V across it. Anyway, there exist a bunch of circuits that could interchange the two tubes with only slight diffs in percieved performance. Having the same basing is probably most likely reason though.
regards,
Douglas
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