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previous: bobCT So I starting on my first homebrew ... -- 6/21/1999 12:58 PM

Re: Amp Build....Advice/Opinions

6/22/1999 1:12 PM
Michael Polutta	Re: Amp Build....Advice/Opinions 1. I have one of those Concerts too. I have approx. 500V on the plates. FAR too much for 6V6s. FAR too much. 475 is not much better. You'll definitely have to adjust the bias range as well. I would not make the transition to 6V6s with this amp without replacing the power xfmr. 2. Going to 6V6s will do more to change the tone than changing the phase inverter. It is true, though, that the cathodyne inverter gives less drive to the power tubes than the long-tailed pair. "Toneful" is way too subjective a term to even ask about. 3. Should work w/ 4 6V6s. Just 2 6V6s and you'll really need a higher P-P impedance for a good match. The 6V6 needs approx. double the P-P impedance of the 6L6. 4. The power xfmr has no 5V tap, so you're going to have to make some arrangements to power the tube rectifier filament. Good luck finding room on that chassis for another power xfmr - even a small one. 5. Which do YOU like? Further, how many triodes will you have available? If you don't have enough to do a "blonde-era" vibrato then the question is answered before you ask. I have dramatically rewired my Concert, originally purchased from Torres (never again - UNBELIEVABLY BAD construction!). The distortion channel looks like a Marshall circuit now (except for the lack of solid-state distortion devices!) with a cathode follower and the tone stack last in the chain before the master volume, and I've futzed with the cathode and interstage cap values a lot. The first stage only uses one triode instead of two in parallel. The clean channel's goofy bright switch is now wired like a blackface - with a dramatic improvement in the response (to my ears - not nearly so "honky"). The reverb drive circuit also now looks like a blackface. The phase splitter cap values have been massaged more to my liking. The "Gain" control is now a rotary switch that adds various capacitors in parallel with the treble cap in the distortion tone stack to thicken the sound - this is the ONLY thing remaining from Torres. Good luck, Michael

6/22/1999 1:12 PM

Michael Polutta

Re: Amp Build....Advice/Opinions

1. I have one of those Concerts too. I have approx. 500V on the plates. FAR too much for 6V6s. FAR too much. 475 is not much better. You'll definitely have to adjust the bias range as well. I would not make the transition to 6V6s with this amp without replacing the power xfmr.

2. Going to 6V6s will do more to change the tone than changing the phase inverter. It is true, though, that the cathodyne inverter gives less drive to the power tubes than the long-tailed pair. "Toneful" is way too subjective a term to even ask about.

3. Should work w/ 4 6V6s. Just 2 6V6s and you'll really need a higher P-P impedance for a good match. The 6V6 needs approx. double the P-P impedance of the 6L6.

4. The power xfmr has no 5V tap, so you're going to have to make some arrangements to power the tube rectifier filament. Good luck finding room on that chassis for another power xfmr - even a small one.

5. Which do YOU like? Further, how many triodes will you have available? If you don't have enough to do a "blonde-era" vibrato then the question is answered before you ask.

I have dramatically rewired my Concert, originally purchased from Torres (never again - UNBELIEVABLY BAD construction!). The distortion channel looks like a Marshall circuit now (except for the lack of solid-state distortion devices!) with a cathode follower and the tone stack last in the chain before the master volume, and I've futzed with the cathode and interstage cap values a lot. The first stage only uses one triode instead of two in parallel. The clean channel's goofy bright switch is now wired like a blackface - with a dramatic improvement in the response (to my ears - not nearly so "honky"). The reverb drive circuit also now looks like a blackface. The phase splitter cap values have been massaged more to my liking. The "Gain" control is now a rotary switch that adds various capacitors in parallel with the treble cap in the distortion tone stack to thicken the sound - this is the ONLY thing remaining from Torres.

Good luck,

Michael