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previous: Darren If you wanted to stay with the AB76... -- 1115004233 View Thread

Re: ab763 tremolo replacement

5/1/2005 10:08 PM
Greg SimonRe: ab763 tremolo replacement
You could also just stay with the trem you have and move it in the circuit. Add a couple 220k resistors to isolate bleed back from each channel and inject the trem before the reverb. As you go earlier in the circuit, you'll get more depth to the trem, but also may get thumping and have to change resistor values, cap values, and/or voltages that the trem operates at. Unless you use a switch to isolate the trem from channel to channel, then basically by making the trem work on both channels, you make the reverb work on both channels too.  
 
I added trem and reverb to both channels on my brother's Silvertone. The amp already had a roach trem that sounded good, but they only had it on channel 2. I did a 3 prong grounding mod which freed up the ground switch, so I can flick the switch and the trem operates on one channel or the other. This way I don't need the 220k isolating resistors. The trem injects after the first gain stage on both channels and is a very deep and pleasing effect. The other benfit to having the switch there is that the gain drop doesn't happen to channel 1 when the trem is selected on channel 2 and vice versa. The reverb was changed to the Fender reverb circuit and it works on both channels too. I have a couple more bugs to fix but it is sounding nice and looking like it will work well.  
 
 
The diode clamp is an idea thats been suggested for the Princeton trem among others and I've not tried it yet myself, although I am using it in a build...it just isn't done yet. It is supposed to work well though. The only difference when using the diode is that the thumping goes away, and the plate voltage actually goes up when the trem is in use by about 15 volts if I remember correctly whereas without the diode, the plate voltage drops by around that same amount.  
 
Greg

 
Replies:
Darren heh cool, glad my diode clamp idea ... -- 5/1/2005 10:51 PM