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Old 21st January 2012, 04:17 AM   #1
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Default old console amp

My first tube amp... I mainly mess around with SS car audio. I Just saved a little 1962 Admiral tube amp from a console that was getting thrown out. The owners manual and schematics were tucked away inside the console. Its a stereo tube amp model 3G2- it has one 12AX7A and two 50EH5 tubes on it. No power transformer? The output transformers stick off each end of the casing. After studying the schematics and nervously adding a switch and power plug I was able to fart around with it and get it going on the test bench with a couple of bookshelf speakers and an ipod. It doesnt have much output, but the sound is perfectly listenable. I think I will clean it up, and upgrade it some and just enjoy it for what it is. It has a big ol honking dry electrolytic cap sticking up off the top right next to the tubes that will have to go somewhere else to make it presentable. Anyone have anything similar or have any suggestions as to what would be reasonable upgrades? I can already see that a larger tube amp is somewhere in my future. This little thing is really neat.
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Old 21st January 2012, 04:47 AM   #2
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Turn it off!!!!

Now, fit an isolating transformer in the line supply, replace the 'lytics and thank whichever god you acknowledge for your own continuing existence...
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Old 21st January 2012, 04:48 AM   #3
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That honking dry electrolytic cap has to go to trash bin, of course. And you need an isolation transformer, please don't power it on without isolation from the power outlet!
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Old 21st January 2012, 05:15 AM   #4
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Mine wasn't so up-market (only had 2 x 50EH5) Note that it has an isolation transformer.

5-Buck Amp

Click the image to open in full size.

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Old 21st January 2012, 05:26 AM   #5
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Im listening guys- please educate me about the isolation trans. Im not real knowledgeable about the tube amps but I did notice there did not seem to be a third transformer anywhere in the console or on the schematics. The way I wired it duplicated exactly the original power feeds from the schematics... unless I'm missing something.
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Old 21st January 2012, 05:29 AM   #6
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I did realize the case was 'hot' and was careful. I'm comfortable enough working around with it on the bench.
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Old 21st January 2012, 05:32 AM   #7
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I believe 50EH5 should be exceptionally nice in triode, while in pentode it looks quite curved.
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Old 21st January 2012, 05:42 AM   #8
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I never ran mine in triode, but it sounded quite good in pentode/no feedback (a current amp i realize now).

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Old 21st January 2012, 05:42 AM   #9
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Quote:
Originally Posted by hollbrow View Post
I did realize the case was 'hot' and was careful. I'm comfortable enough working around with it on the bench.
yeah, well, electrons are not too concerned about your care - or the ignorance of others. Fit a power transformer to isolate the circuit from the line supply. You don't have the economic imperative excuse of the manufacturer.
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Old 21st January 2012, 06:10 AM   #10
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Will do on the isolation transformer. I recognized there were some issues there- just wasnt sure what needed to be done about it. I appreciate you guys pointing that out. So in tube amp jargon, what exactly would this amp be called?
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