• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Need ideas for my 6V6 from 1946 Blues / rockabilly

I bought a turntable unit from a thrift store this weekend. it turns out to be a modified 1946 philco. The tubes are 5Y3GT, 6V6GT, 6V6GT, 7X7, 7AF7. The transformer is the original Philco 32-8248. there is a seperate preamp unit that was added which is a Calrad model pre-105 that uses a 6SC7.

I am more than proficient in electronics and I am a Ham Radio Operator. So fear not I will not electricute myself.

What I would like to do is to rewire this amp into a nice flexable jazz, blues / rockabilly amp. I would like to have plenty of tuneability to it.

I have a 1967 Hagstrom Viking II that I will be using with the amp.

Currently the amp powers up and runs fine however there is still some remnants of the screw adjustable equalizer in the circut and I dont know what else. there are two knobs controling the volume and possibly a tone control?

the person who modified this unit has it runing three speakers on 12 and two 8's. It play ok with the currents setup, but the sound from the 1st string, the highest notes are very very quiet, I am asuming this is due to a missing part of the screw pot equalizer.

I know that once I rewire everything that this old amp will be rockin, so guys what ideas do you have?


2008-01-08 12:22 am
What I would like to do is to rewire this amp into a nice flexable jazz, blues / rockabilly amp. I would like to have plenty of tuneability to it. ...

Do you mean for playing that genre of recorded music or do you want a blues/jazz guitar amp? Certainly for guitar I'd look at early Fender schematics like the "baseman" and build a lower powered 6v6 versin of that.

For recorded music mid-fi 50's style. It depends do you need a phono preamp
I guess what I am trying to say is that I would like to build an amp that has the capability of producing the sounds of the early bluesmen, early jazz guitar like djanjo reinhardt, and rockabilly like carl perkins, early elvis, johnny cash, Brian Setzen, Reverand Horton Heat.

I have what I have for parts and dont have a lot of money to go outside of what I have so I am hoping that there is an existing schematic for something that will work well with what I have.

Mag. phono preamps, like that Calrad, roll the HF off. That's done to correct for the HF boost/LF cut introduced at mastering time. You need to remove the equalizing caps. and resistors.

The 6SC7 is somewhat tricky to work with, as both cathodes are tied together and connected to single pin on the base. Your Calrad probably follows the GE model and uses grid leak bias to get around that common cathode connection. An alternative to that technique is a red LED between the cathode connection and ground.

The schematic for the Gibson GA-20 Lars suggested is here. It looks straight forward enough, but the tube complement does not match what you have. You could substitute the 6SC7 for the 6SL7 easily enough, but you would have to buy 6SJ7s.

Whatever circuit you decide on, don't forget a proper, safety grounded, 3 wire power cord.
Excelent! I did a little youtube research and YES YES YES!!! thats the sound I would like to have. also the cabinet looks cool and easy to reproduce.

so I guess I will have to come up with a couple of tubes I dont have currently, but those dont seem to be that expensive..

Anyone here built a GA 20? I would like to see some pictures of their build if possible.