After much soldering I think I might be done. I have two OD gain stages that can be switched in front of the Fender-like clean channel. In OD mode there is a good amount of gain available. Here is the schematic:
Since this used to be a Dumble type amp I had some switches available so, of course, I have to come up with something. The Brit/American switch in the tone stack is actually pretty handy. It changes the tone stack from something close to a Blackface type to something close to a Marshall. I’ve found that in OD mode in the American setting you can turn down the mids and get close to that high gain, scooped mids Mesa sound or in Marshall mode you can get a pretty good high gain Marshall sound. I think that somewhat strange topology lends it self to being able to go Marshall or Mesa.
Another good sound is with the tone stack in American mode and switching in the OD circuit with the the OD set to low. With a strat you can get some really nice, just breaking up sounds. With this setting having the tone control on the overdrive comes in handy too.
It’s a pretty versatile amp and can get a lot of good tones but my problem now is that its a combo and I’m not crazy about the speakers I have. I’m not going to go buy 2 12s just for this so I think I’m going to build some sort of head cab for it so I can use it with my good speaker cabinets.
I’m also considering putting a choke in it. I think it would really be a good addition.
Here is a gut shot. It could be cleaner but not too bad considering how much experimenting went in to this one (and that is started out as a Crate Blue Voodoo).
That transformer inside the chassis is a “bucking” transformer to bring the voltages down a bit. The stock Crate power transformer got me a little over 500v on the plates and I wanted to lower it. The bucking transformer works great.