50's Baldwin tube amp

[baddog]

This amp is a 2 channel amp without a preamp. I would like to add a preamp for each channel.

channel 1 tubes
1 12ax7 inverter
2 7027 power tubes

channel 2 tubes
1 12ax7 inverter
2 6l6 power tubes

The rectufiers are 2 5U4's ran together simular to a fender 5E6 layout

does anyone have a simple design preamp i can put in front of each channel.
I think this is a 50 watt amp from what i read on the net.

[metalangst]

Do it. Put a "champ style" pre-amp in front, simple and dirty. Did you want to shred in stereo? If not, look at some hi-fi schematics. You may find a basic design to use. Or just hook up a receiver, preferably with eight-track. What do you want to use the amp for?

[baddog]

I want to use both channels for guitar . Basicly 2 amps in one. I would like to use 2 diferent preamps so i have 2 different amps. I am more of a blues / blues rock guy. I have pedals for my Metallica moments.

thanks
keith

[metalangst]

A champ pre-amp would work, but you may want more control over tone. I like the ampeg style pre-amp, the bass and treble controls are more defined than the fender/marshall/etc. I built an amp with one each on the two channels. Check out some old tube amp schematics. You use everything up to the phase inverter, or output tube if it's single ended. Those ampeg circuits can be simplified, remove the tone switches. pick any amp you like the tone of and modify the pre-amp to suit your needs.

[Steve Conner]

It can't possibly be stereo, as it only has one output transformer. It must be running all four 6L6 together for 100 watts.

(If two of the sockets are marked 6L6 and the other two 7027, then there's something really weird going on. But if that was just what tubes you found in it, then all four should be the same.)

[baddog]

It has 2 output transformers. One is in the chassi

[Steve Conner]

Hmmmm, so what's the other lump on top of the chassis, a choke? Or is it one of these old amps that had two different OTs, for matrix stereo, or main and reverb channels on an organ or whatever?

[baddog]

HI

yes the one on top is a output transformer also. it has 2 seporate amps on one chassi. Each channel had its own blue framed alnico 15" jensen speaker .

keith

[PRNDL]

In your amp, there's an unused tube socket where you can add a 12AX7 preamp for 2 gain stages with a standard tone stack & volume in between. You can connect the output to both wires currently connected to the two mono input jacks. (Check to make certain there's a coupling cap).

You can neaten the chassis a bit by removing the wires to the speaker connectors on the top of the chassis, since you'll be using the output jacks on the side.

The next issue is the volume pots on the top of the chassis. You may want to move them to the front of the chassis.
You might want to figure out how they are wired, but don't have to. With different speaker transformers, there will be different volumes and this is a handy way to match them. (Another issue is figuring out speaker impedance, which may be different for both sides.)

Figuring out a front panel layout will take some thought.

Those bumble bee caps are another issue. Don't throw them away -- they're collectors items. They sound weird when they get old, and you may get a dramatically different tone by replacing them with yellow mallory or orange drops. That will also free up some room on the front panel.

Also consider replacing those cap cans. Usually they work for a while and then melt nasty black goop everywhere. The easiest is to get direct replacements.