Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Colas LeGrippa on April 02, 2012, 11:43:16 am
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Hi, I just found a Fender amplifier ( story is too long to tell ) SUPER REVERB model and I am looking for nice mods to increase the gain. I don't mind cancelling the reverb if necessary. Any idea ?
Colas
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1. Raw control... Replace MID pot with a 250K pot.
2. Replace 3.3M resistor with 3.3K resistor. Lot's more gain but kills reverb.
3. Replace INT pot with 50K pot with SPST switch wired in series with the pot for a gain boost.
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Disconnect the NFB wire and tape it off, remove the tube in V1 is not using normal input. Lower the cap values. I am assuming you have a silverface non-mv version. Blackface it and get control over you bias. Marsh sells a blackface kit (you don't really have to buy the kit, you can just compare the schematics to an AB763. It is nothing but a few resistors and upping he uf on the filter caps. and Gerald Webers book Hip Vintage Amps has a section on 10 things to do to a super which really work well.
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Also read this as it has great info on doing whatever you want.
http://fenderguru.com/amps/super-reverb (http://fenderguru.com/amps/super-reverb)
Also, I forgot. The speakers is Supers are not really good. I put Weber alnicos 20 watters in the top and 30 watt ceramics in the bottom. If he baffle is particle board, change it to birch. Simple thing to do. I have 4 super reverbs and looking at another one. I collect them. I hope this helps.
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Thanx guys for great infos, I love you.
Colas
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2. Replace 3.3M resistor with 3.3K resistor. Lot's more gain but kills reverb.
1.2-1.5M is a good compromise.
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If you keep the normal channel, cascade the two stages and put the tone stack afterwards. Change shared cathodes, lower coupling cap(s) and cathode bypass caps to taste. Simple and effective. Remove the polarity switch in the back and replace it with a pushpull pot and create a Presence control that can be switched out of circuit too.