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previous: Mike Instead of the doubler setup, will ... -- 10/27/1999 7:09 PM

Re: Why change the PS (voltage doubler) setup?

10/28/1999 12:12 AM
Farrow	Re: Why change the PS (voltage doubler) setup? If the PT doesn't have a CT then I wouldn't try to "fake it." It's much easier and safer to make a full wave bridge rectifier setup. Use the 2 diodes in th GZ34 for the "forward" diodes in the bridge and 4 1N4007s for the reverse diodes. (2 in series x 2) This way you still get the sag of a rectifier tube (tho not all that much from a GZ34) but you don't need the CT for the full-wave rectifier. This also works GREAT in 80's Rose-Morris AC30s, BTW. Although there I'd use a GZ32 (5U4) which is a little easier on pwoer tubes. Pumpstein, I usually remove the doubler because it takes up more than half the real estate inside the amp, involves lots of components and can be unreliable and dangerous. YMMV, of course, but simply replacing the PT with one that can deliver the needed B+ voltage in the first place is MUCH more elegant. The thread was originally "mods for the Twin Twelve." BTW if you want to see some amazing amp design, check out the old Wards Airline amps with 4x6L6s and 2 OTs! They use 12AX7 heaters as cathode resistors -- you get free DC heaters on your preamp tubes. Plus they sound AWESOME esp. into a 6x10 cab. Eat your heart out! Farrow http://surf.to/pharaohamps

10/28/1999 12:12 AM

Farrow

Re: Why change the PS (voltage doubler) setup?

If the PT doesn't have a CT then I wouldn't try to "fake it." It's much easier and safer to make a full wave bridge rectifier setup. Use the 2 diodes in th GZ34 for the "forward" diodes in the bridge and 4 1N4007s for the reverse diodes. (2 in series x 2) This way you still get the sag of a rectifier tube (tho not all that much from a GZ34) but you don't need the CT for the full-wave rectifier. This also works GREAT in 80's Rose-Morris AC30s, BTW. Although there I'd use a GZ32 (5U4) which is a little easier on pwoer tubes.

Pumpstein, I usually remove the doubler because it takes up more than half the real estate inside the amp, involves lots of components and can be unreliable and dangerous. YMMV, of course, but simply replacing the PT with one that can deliver the needed B+ voltage in the first place is MUCH more elegant. The thread was originally "mods for the Twin Twelve."

BTW if you want to see some amazing amp design, check out the old Wards Airline amps with 4x6L6s and 2 OTs! They use 12AX7 heaters as cathode resistors -- you get free DC heaters on your preamp tubes. Plus they sound AWESOME esp. into a 6x10 cab. Eat your heart out!

Farrow
http://surf.to/pharaohamps