Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: roseblood11 on October 21, 2017, 02:51:59 am
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Hello,
I'm planning a small two channel amp with a Friedman BE channel and a Fender Brownface channel (like 6g3, but with switchable TMB tonestack). Power amp will be two 6v6 with fixed bias and an OT with 6.6k primary.
How would you choose the values for the ltp phase imverter and why? I think the PI plays an important role in the overdriven sound of both channels. So, what would be a good compromise?
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Power amp will be two 6v6 with fixed bias and an OT with 6.6k primary.
I consider the PI to be part of the power amp. So, I'd just copy the entire poweramp of a Fender AB763 Deluxe Reverb. May as well copy the power supply too.
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Why do you recommend the AB763 Deluxe Reverb? The power amp is quite different from a 6G3 or other small brownface amps.
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Because the AB763 circuit is probably the most successful and popular amp Fender ever made. Anytime someone mentions p/p 6V6 with fixed bias the DR pops to the top of the list in my mind.
The power amp schematic is exactly the same as the 6G3 except for the NFB and PI tail resistor values and the use of a 12AX7 rather than 12AT7. I'd say the power amps are nearly identical, not quite different.
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We'll see...
Maybe I'll even try a cathode biased power amp, as Marshall did in the P.A. 20 (1917)
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Excellent idea. Once you decide not to use fixed bias 6V6s you should have plenty of choices for power amps. It should be easy to marry the Fender preamp to most any power amp. Can't say about the Friedman. Never seen a schematic.
The 1917 uses EL84s, not 6V6s.