Building amp from an old tube radio

[flintrock]

Hey guys, I'm wanting to build a guitar amp from an old 1941 Silvertone (Zenith) radio. Its a 6K6 PP with a 5Y3 rectifier. I have a few extra chassis laying around, and really I may only use the transformers from this radio. I have 372v off the PT, and 289v at the 6K6 plates. Would like a TMB tonestack and a couple of gain stages. If the PT is sufficient I wouldn't mind using 6v6's for more output. Maybe something early Gibson for that heavenly blues sound. Anyone have any ideas or schematics/layouts that might work?

[Leo_Gnardo]

I don't see why your B+ drops from 372V at the PT and only 289V at the 6K6 plates. No matter - looks like your iron would support a 6V6 PP amp. You could go to a 5AR4 rectifier or silicon for more power. OTOH the older amps often had a mellower tone partially due to lower supply voltages. Your choice, or you could put in a switch to select tube or SS rectifier.

Could do a Princeton style circuit, with an added midrange control.

[flintrock]

Definitely could do that, looks simple. I would omit the vibrato though. Hmm...Fender or Gibson..

[flintrock]

Original rectifier tube is a 5Y3, I am interested in more output is it as simple as changing the rectifier circuit? I'd like to keep it tube rectified for that vintage vibe.

[Leo_Gnardo]

Unless the limiting factor is the power transformer, you can expect a bit more hi voltage, therefore power will rise, by using a 5AR4/GZ34. Advantages also - only a 2 amp draw on the 5V filament and slow warmup so you could leave out a standby switch.

[darryl_h]

I have 372v off the PT, and 289v at the 6K6 plates.

This seems to be a remarkable drop. Does the radio's speaker have a field coil magnet perchance? That would explain the voltage drop.

[flintrock]

Yep good guess! It does have a field coil speaker. However I won't be using it since the cone is toast.