| Author |
Topic: Twin: Modify the first channel to three reverb c |
Chris Erbacher
From:
Sausalito, California, USA
|
Posted 31 Jan 2006 3:35 pm |
|
| hey guys, just wondering how one would go about modifying the first channel of a twin to instead be a three knob reverb control, tone dwell and mix? i may be going overboard, but why not if the extra channel is there getting no useage? just wondering how i could go about doing that. thanks in advance... |
|
|
 |
Papa Joe Pollick
From:
Swanton, Ohio
|
Posted 31 Jan 2006 4:57 pm
|
|
| Chris,I have done the mod suggested by Gerald Weber, in his book "Tube Amp Talk for the Guitarist and Tech"..Very simple to do.You will have a "mix" control on your "vol".,and tone controls on the reg."tone controls".But no "dwell" unless you want to go farther.At this point the "rev" control will be disconnected.It worked fine for me when I tried it..If you decide to try it, and none of the more knowledgeable guys jump in here to advise you,I'll be glad to pass the info that I have. PJ |
|
|
|
Jerry Erickson
From:
Atlanta,IL 61723
|
Posted 31 Jan 2006 5:36 pm
|
|
| I've added the dwell control to one of my Twins and like it. I like to be able to use both channels as I sometimes double on guitar and steel so I probably wouldn't do the tone control mod. As PJ suggested, get the Weber book. |
|
|
|
J Fletcher
From:
London,Ont,Canada
|
Posted 31 Jan 2006 5:40 pm
|
|
To add a three knob reverb circuit to a Twin Reverb is a pretty big mod, if you are going to do it like a stand alone reverb. Can be done though. Half of the 1st 12AX7 would be the voltage amp to drive the rev driver tube, and the Dwell control would determine how much signal is passed to the 12AT7 rev driver from the voltage amp.The other half of the 1st tube would be the cathode follower for mixing the dry signal with the rev signal.
The reverb recovery tube could then be configured like the stand alone reverb circuit, and that is where the tone control, and the mix control would be, on the output of the rev recovery stage.
You would have to mess around with some resistor and capacitor values to get everything balanced out, and sounding good. Don't know if you would need the 1/2 section of the 12AX7 that would be left over, which is normally used as the rev and dry signal mixer tube. You might have that left over, or you might need it to boost the signal to the rev driver tube, or as another rev recovery stage tube.
Having said all that, it's pretty hard to beat the stock reverb circuit in a Twin. My opinion is that it sounds better than the three knob circuit....Jerry |
|
|
|
Mike Fried
From:
Nashville, TN, USA
|
Posted 31 Jan 2006 10:05 pm
|
|
| A temporary or "poor man's" version of this mod is to disconnect the reverb return lead (which plugs into the "input" RCA back panel jack), extend it and use a 1/4" phone plug adapter to plug it into the normal channel's "2" input. This uses the normal channel as the reverb return amp and provides tone controls. Some gain reduction of that channel may be in order, easily accomplished by replacing its 12AX7/7025 with a lower-gain sub such as a 5751 or a 12AT7. BTW, the original "reverb" control should then be turned off as it is no longer operating and will raise the noise floor if it's on at all. |
|
|
|
Papa Joe Pollick
From:
Swanton, Ohio
|
Posted 31 Jan 2006 11:09 pm
|
|
| Mike, didn't you mean to say,plug in-to the rev. "out" on the back plate? PJ |
|
|
|
Papa Joe Pollick
From:
Swanton, Ohio
|
Posted 1 Feb 2006 7:00 am
|
|
| I stand corrected Mike..It was past my bed time when I posted last night.sry.PJ |
|
|
|
