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In Reply to: RE: CARY 40M Special ... with Cap Input posted by Caucasian Blackplate on January 25, 2015 at 18:14:48
With 500V B+, how Class A could it be? I always have some misgivings about that claim but never have an answer.
Follow Ups:
It's cathode biased, so once you leave class A, things will fall apart very quickly, and clipping will be severe.
Fixed Biased.
The manual says auto cathode bias.
You are correct about the manual. Delivered amp is a different story: fixed bias. I bought the amp new. The schematic in the manual is far from accurate and I had to trace the circuit. Fortunately not too complicated even for an amateur like me.
Hello,
I have done 31 emails in two days to get this amp documented. NOT YET do I know what is stock !!
BTW, the schemo sent from Aussie land is FIXED bias.
Are there published voltage readings, around the 6SL7 Pins, etc, for this amp ?? My guy in Aussie land is telling me 0.66 VDC of self bias on the input stage's Rk, ............and I say "B.S.", too low.
Have YOU ever recorded all the key voltages of the stock amp ?? If so, would you be kind enough to email me same, so I can figure out what is normal and what might be done to improve this amp ? My email address is above.
I have some great, low risk, medium-cost mod ideas on this, but need to get the stock values and voltages as the starting point, properly documented. Be happy to share ideas on this with you privately. Thanks a lot !!
Jeff Medwin
If it is indeed fixed bias, that would suggest that it is designed to slip out of class A, and in that instance, one would want as little impedance as possible between the OPT center tap and the output of the rectifier diodes.
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