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BrandNoob
The REALAmerican Hero!



Registered: 07/15/07
Posts: 717
Loc: Potland, OR
Last seen: 13 years, 9 months
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Amp Tech? Someone who knows about modding guitar amps?
#7534565 - 10/19/07 09:08 AM (16 years, 3 months ago) |
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I think this is the correct forum for this, if not - mods please help me move it to where it belongs.
A guy showed me this cool trick once. If you have a tube amp with a reverb tank, but want an extra gain stage more than you want reverb, you can remove the RCAs and place the appropriate value resistor through the plugs. Like literally stick its legs into the RCA jacks - no soldering.
I need to know what an appropriate value for that resistor would be. Not just the ohms, but the minimum wattage handling for it. I think I need a 1 watt resistor at around 100 ohms. Can anyone confirm this?
This trick was first shown to me on a silver-face Fender Twin Reverb with a master-vol. Will this work on a 70's Carvin?
The reason I'm asking is that we have an old Carvin head at my work - but the entire reverb tank is missing. I figure an extra footswitchable gain-stage would be a good trade-off, since most people don't use reverb on their half-stacks anyway. I hope I didn't bore anyone, thanks for any suggestions.
-------------------- All posts were channeled through the user by typing the thoughts of telepathic beings. All photos are of paranormal origin and do not represent the physical world, as we know it. BrandNoob shall not be held accountable for the actions of deceased or hyperdimensional individuals.
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El Zorro
in heaven
Registered: 03/21/07
Posts: 902
Last seen: 2 years, 26 days
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Re: Amp Tech? Someone who knows about modding guitar amps? [Re: BrandNoob]
#7535185 - 10/19/07 12:13 PM (16 years, 3 months ago) |
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The fender reverb tapped a signal between the second and third gain stage ran it through a 12at7 then the tank and reinserted it before the third gain stage. So what you were doing is using the 12at7 which is a medium gain tube to amplify a small portion of the dry signal then pumping it back in before the final gain stage. I don't know how your Carvin is designed but it may or may not work.
However, A 12at7 typically runs about 2.5 watts. So I wouldn't use a 1 watt resitor for this. I don't know off hand what the impedence of the reverb tank is but you can get an idea by measuring the dc resistance.
Actually I wouldn't do this at all. Doesn't sound like a good idea. There are much better ways to use the unneeded reverb channel. Besides I wouldn't trade onboard reverb for gain, ever. Just use a pedal.
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WhiskeyClone
Not here


Registered: 06/25/01
Posts: 16,509
Loc: Longitudinal Center of Canada ...
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Re: Amp Tech? Someone who knows about modding guitar amps? [Re: BrandNoob]
#7535470 - 10/19/07 01:27 PM (16 years, 3 months ago) |
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-------------------- Welcome evermore to gods and men is the self-helping man. For him all doors are flung wide: him all tongues greet, all honors crown, all eyes follow with desire. Our love goes out to him and embraces him, because he did not need it. ~ R.W. Emerson, "Self-Reliance"
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BrandNoob
The REALAmerican Hero!



Registered: 07/15/07
Posts: 717
Loc: Potland, OR
Last seen: 13 years, 9 months
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Re: Amp Tech? Someone who knows about modding guitar amps? [Re: El Zorro]
#7536904 - 10/19/07 07:37 PM (16 years, 3 months ago) |
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Quote:
El Zorro said: The fender reverb tapped a signal between the second and third gain stage ran it through a 12at7 then the tank and reinserted it before the third gain stage. So what you were doing is using the 12at7 which is a medium gain tube to amplify a small portion of the dry signal then pumping it back in before the final gain stage. I don't know how your Carvin is designed but it may or may not work.
However, A 12at7 typically runs about 2.5 watts. So I wouldn't use a 1 watt resitor for this. I don't know off hand what the impedence of the reverb tank is but you can get an idea by measuring the dc resistance.
Actually I wouldn't do this at all. Doesn't sound like a good idea. There are much better ways to use the unneeded reverb channel. Besides I wouldn't trade onboard reverb for gain, ever. Just use a pedal.
Wow. Thanks for the info. It was just a cheap trick someone showed me once - I knew that it sounded too good to be true. Oh, well! Come to think of it, that guy's Twin sounded like garbage. I just blamed it on CBS at the time, but he was probably pretty close to meltdown. Those amps aren't really voiced for high-gain anyway.
The Carvin head is just sitting around right now. It's got channel switching, plus a footswitchable lead boost so if I did add another gain stage, it would probably just self-oscillate anyway.
Maybe I'll just try and score a cheap accutronics tank off Ebay and toss it in the box. And then raise the price and compensate myself for the labor, of course 
Either way, I'm gonna go rate the shit out of you now.
   
-------------------- All posts were channeled through the user by typing the thoughts of telepathic beings. All photos are of paranormal origin and do not represent the physical world, as we know it. BrandNoob shall not be held accountable for the actions of deceased or hyperdimensional individuals.
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