Hello, steemians, and welcome to the workshop, eh!
This is another tube amplifier that I've been working on a bit at a time for a fairly long time. This amp started out as the amplifier for an old record player. According to my picture files, this amp was given to me in 2015, and I've been messing with it ever since. I'm pretty sure that I've rebuilt this amp at least 4 times now, trying to get it to sound good as a guitar amp. Before I get too far into this, let's take a look at the amp as it was when I got it. The picture quality is not the best here, my camera doesn't always focus where it should in close up shots.
The first thing I had to do was strip out all of the old parts that couldn't be used as part of a guitar amp. That meant pretty much all the small parts. I started on the first rebuild in January of 2016.
Then I had to drill various holes in the chassis for the extra preamp tube sockets and all the controls, as well as replacing the power supply capacitor can. 50 year old power supply capacitors are quite unreliable.
I replaced the existing preamp tube socket with a new one, and added 2 more preamp sockets for the circuits that I had in mind for the amp. I also replaced the power cord, which was cut off when the amp was given to me.
Then came all the rewiring for the guitar amp circuits. This thing was difficult to work on due to the tight space in the chassis. Here you can see all the internal parts including the back side of the controls.
The front with all the controls, without the knobs.
The first circuit arrangement didn't work out all that well in testing, so I kept tinkering with it off and on when I was in the mood. I don't do very much of this kind of work in the summer, so time went by with out having the amp working the way I wanted it to work.
Since I've been working on other amps this past winter, I finally decided to get it back out and mess with it again to see what I could do with it. I decided to simplify the preamp circuits back to a basic Fender design used in some of their small amps such as the Princeton, except with 3 tone controls instead of 2, because I like having a midrange control as well as a bass and treble control. I also realized that I had been expecting too much from this little amplifier. This is a low power amp, it wasn't designed to get very loud, it probably puts out about 8 watts of power. I don't think it puts out 10 watts because it doesn't get as loud as my little 10 watt amp that I built.
I had to pull some of the parts out of it to rewire it to the simpler design, but that's pretty much the way it goes when you rework one of these amps. This is what it looks like now. It has a gain control, a volume control, and the 3 tone controls.
The inside wiring is a little bit less cluttered and messy, simply because there's a few less parts in it now.
To test it after rewiring it and checking the voltages to make sure everything was working correctly, I plugged one of my 12 inch speakers into it and played the guitar through it. It doesn't get all that loud, but it sounds pretty good for a small amp. Depending on the volume settings, it can sound anywhere from clear to rather distorted, with a fair amount of adjustment within that range of sound. The tone controls don't have quite as much control as I would prefer, but they do have some range of adjustment. I could probably mess with changing certain parts in the tone circuit to see how it affects the sound, but I think I'll just leave it as it is now. I would like to build a cabinet to mount the amp and a speaker in, but that's going to have to wait for warmer weather when I can cut the wood outside.
Well, that's all I have for this post, I hope you found it interesting!
Thanks for stopping by and checking out my post, eh!
Feel free to leave a comment or a question for me if you would like.
May the Steem Force be with you!
Holy Shit!
MacGyver
Yeah, sometimes it feels like that... :-)