Fender Twin Reverb Modifications
Moderator: jingle_jangle
Fender Twin Reverb Modifications
Charlie: I have a 1970 Fender Twin Reverb that has a fantastic clean channel that I use pretty much exclusively. Before I purchased the amplifier, it underwent a Torres modification in which the vibrato channel was rewired as a distortion channel. My question is, is it a lot of work to have the vibrato channel put back to its original specs and are the parts to do this still available?
Life, as with music, often requires one to let go of the melody and listen to the rhythm
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Yes
A competent tech should be able to "de-mod" the Torres distortion mod to stock. All the parts are available. Some tremolo circuits use a neon bulb and a photocell which can be purchased from parts suppliers like MOJO, or CE Distribution. You will need a schematic of the amp to make sure you get all the parts correct.
In my opinion, it is better to use the original circuit than to modify vintage amps, they lose their value and several of the mods are bogus and sound cheesy.
My experience with working on many guitar amps and having to bring them back to stock, usually makes the player happier in the long run.
A competent tech should be able to "de-mod" the Torres distortion mod to stock. All the parts are available. Some tremolo circuits use a neon bulb and a photocell which can be purchased from parts suppliers like MOJO, or CE Distribution. You will need a schematic of the amp to make sure you get all the parts correct.
In my opinion, it is better to use the original circuit than to modify vintage amps, they lose their value and several of the mods are bogus and sound cheesy.
My experience with working on many guitar amps and having to bring them back to stock, usually makes the player happier in the long run.
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soundmasterg
- RRF Consultant
- Posts: 1923
- Joined: Tue Oct 01, 2002 1:06 pm
Charlie commented
Sage advice Charlie. I am wondering if you would apply this philosophy to the Silverface to Blackface modification. Provided the Blackface sound is what one is after, is the SF to BF modification readily achievable."In my opinion, it is better to use the original circuit than to modify vintage amps, they lose their value and several of the mods are bogus and sound cheesy."
Life, as with music, often requires one to let go of the melody and listen to the rhythm
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When it comes to collector value, the most mint and most electrically original amp is the most valuable.
When it comes to modding from SF to BF, it depends on how far the tech went. Most BF mods do not replace the power transformer which has a center tap for the filaments which the SF xfmr does not.
The BF mod is really quite simple, it involves lowering resistor values in the power supply under the capacitor can which result in higher B+ voltage to the output tubes, changing out a few other resistors in the circuit, etc. If you go all the way, you replace the power transformer with an original or replica BF power xfmr.
This results in a little more power and authority with the amp, including better distortion characteristics and better tone. This of course, depends on the condition of the amp, the speakers, the guitar and of course the player.
When it comes to modding from SF to BF, it depends on how far the tech went. Most BF mods do not replace the power transformer which has a center tap for the filaments which the SF xfmr does not.
The BF mod is really quite simple, it involves lowering resistor values in the power supply under the capacitor can which result in higher B+ voltage to the output tubes, changing out a few other resistors in the circuit, etc. If you go all the way, you replace the power transformer with an original or replica BF power xfmr.
This results in a little more power and authority with the amp, including better distortion characteristics and better tone. This of course, depends on the condition of the amp, the speakers, the guitar and of course the player.
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soundmasterg
- RRF Consultant
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Charles, it will be interesting in the next 20-30 years when all the old vintage amp's power supply caps will finally have failed for sure, and the collectors who want something completely original will have to settle for something with new electrolytic caps in it. I'm sure you've encountered the people who don't want to replace the power supply caps even though they should be done for the amp to operate properly if its a bit old?
Also Peter, I'm not sure about the Twin Reverbs, but on the Silverface Deluxe Reverbs, the power transformer voltages are a lot higher, and they used a different rectifier tube too, so to get back to blackface specs on one of those later Silverface Deluxe Reverbs (early 70's is when they switched), you have to change the power transformer in addition to blackfacing the circuit and changing to the GZ34 rectifier tube. That said though, even without going to that step, the Silverface Deluxe Reverbs can be made to sound very nice, and often seem to worth as much or more as they would be without the mods, as long as lots of holes aren't cut into the chassis anyway. Not sure if that applies to other Silverface Fenders though.
Also Peter, I'm not sure about the Twin Reverbs, but on the Silverface Deluxe Reverbs, the power transformer voltages are a lot higher, and they used a different rectifier tube too, so to get back to blackface specs on one of those later Silverface Deluxe Reverbs (early 70's is when they switched), you have to change the power transformer in addition to blackfacing the circuit and changing to the GZ34 rectifier tube. That said though, even without going to that step, the Silverface Deluxe Reverbs can be made to sound very nice, and often seem to worth as much or more as they would be without the mods, as long as lots of holes aren't cut into the chassis anyway. Not sure if that applies to other Silverface Fenders though.
I will be getting a new Kustom "36 Coupe" all-tube amp in the next couple of weeks. Once I get it in and try it out against my vintage tube amps, I will post my impressions. I do already have one of the recent TRT series, but it arrived with a bum reverb tank that I need to replace before I try it out.
It is better, of course, to know useless things than to know nothing. - Seneca
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trancedental
- Junior Member
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I blackfaced my battered '72 SF Dual Showman Reverb top & removed the Master Volume switch/ & a few other mods including the negative feedback mod.
Installed Brimars/Mullards & a NOS set of GE 6L6's for the tubes.
It's sounds much warmer, breaks up earlier as well. Before was sterile & harsh sounding.
Restored it & put it in a Twin Reverb 2x12 cab new grillcloth etc tolex, it looks like a TR 65, reissue now LOL!
Bet it sounds better than one as well!
Installed Brimars/Mullards & a NOS set of GE 6L6's for the tubes.
It's sounds much warmer, breaks up earlier as well. Before was sterile & harsh sounding.
Restored it & put it in a Twin Reverb 2x12 cab new grillcloth etc tolex, it looks like a TR 65, reissue now LOL!
Bet it sounds better than one as well!
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Another great mod for the solid state rectifier Twins and Bassmans is to replace the 1N4007 silicon diodes with IXYS HEXFREDs, the 1200V 11 amp ones. They are very quiet, smooth and sound excellent. Lower noise levels, and better regulation.
Easy to install, just use a heat sink or hemostat when soldering the leads in place.
We have them for $7.00 each. You can buy them cheaper if you get 50 pieces or more.
Easy to install, just use a heat sink or hemostat when soldering the leads in place.
We have them for $7.00 each. You can buy them cheaper if you get 50 pieces or more.