So let me start out by saying although i work work electronics for a living, I am fairly uncomfortable with tube amps. Aside from the basics knowing how to drain caps, etc. and replacing a few pio caps that have burnt out, I have very little experience modifying, and essentialy re engineering these vintage circuits.
I have been playing guitar for a couple years, and have acquired a few tube amps,(b52 st6012, 1959 gibson skylark ga-5) and I have fallen in love with everything from the sparkling cleans, to the naturally compressed overdrive, to the straight tube distortion. I would like to modify this amp to give me some, if not all of these characteristics.
The amp is out of a 1951 Silvertone organ. The amp is a simpson-sears, model # 157.47211 tube layout is as follows, two 12ax7a's, 6aq5a, 5y3. The organ worked great when purchased, and my trouble is I cant seem to find a schematic on the amp. I would like a gain, volume, and treble control. Possibly a master volume, but if the amp is around 5-10 watts like I am assuming, it probably isn't necessary. I aprecciate you guys helping me out, and I look forward to any responses.
Thanks
I have been playing guitar for a couple years, and have acquired a few tube amps,(b52 st6012, 1959 gibson skylark ga-5) and I have fallen in love with everything from the sparkling cleans, to the naturally compressed overdrive, to the straight tube distortion. I would like to modify this amp to give me some, if not all of these characteristics.
The amp is out of a 1951 Silvertone organ. The amp is a simpson-sears, model # 157.47211 tube layout is as follows, two 12ax7a's, 6aq5a, 5y3. The organ worked great when purchased, and my trouble is I cant seem to find a schematic on the amp. I would like a gain, volume, and treble control. Possibly a master volume, but if the amp is around 5-10 watts like I am assuming, it probably isn't necessary. I aprecciate you guys helping me out, and I look forward to any responses.
Thanks
It is a little bit of work but you could draw out the schematic by copying the parts in the amp. Put the tubes in the layout they are in, fill in the capacitors and resistors, then redraw it to closer resemble normal schematics. I would say a 6G2 Princeton without the temolo and run cathode biased on the outputs would be a good place to start.
http://ampwares.com/schematics/princeton_6g2.pdf
http://ampwares.com/schematics/princeton_6g2.pdf
I appreciate the response, and advice. So I got a little impatient last night, and where the little "microphone" was, I unsoldered and added a 1/4" guitar jack. Fired it up, let it warm up and nothing. I am suspecting rather than a true microphone, this is actually a peizo crystal? Still kind of confused why I had no input. The input of the "microphone " goes into pin 2 of the first 12ax7 thru a resister, and also another resister goes to ground from the same terminal. I'm hoping that my little experiment didn't cause any harm to the amp, but there was no smoke, noise, or smell so I am hoping it will be OK once the corrections are made. I would like to keep most or the circuit the same, keep the tremolo and power section the way it is, and just hopefully rewire the preamp section to remove unnecessary anti feedback circuits, and maybe make it so I can get some nice grind out it at high volumes. Considering there is two 12ax7's it should be possible. I'll include some pictures, and once again thank you guys for your help on my first build 🙂
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