Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Pastortom on July 18, 2012, 09:44:13 am
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I'm re3ading a tech report on removing the tick from a Silverface Fender Vibrolux...... (All cable dress issues have been resolved, and other common problems checked.....no change).
I understand the premise of filtering the output of the opto from the 10meg to ground, but it states to use a .02 cap.........Help out a novice here a bit, and give me a second opinion......exactly what cap and type of cap should I use for this purpose? Any specific suggestions ? Anyone done this and had good luck with a specific ? :worthy1: :dontknow:
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I've tried a couple of variations of the ".02 cap from 10 meg to ground" solutions for this, and each time I get my hopes up but find the result is less than spectacular. My experiences with this always end up the same: the cap just makes the ticking darker and at the same time bleeds some of the signal to ground so that the signal through the tremolo channel is degraded to the point where I wouldn't want to use it. I always end up undoing the cap to ground and just living with the ticking because the fidelity is much better without the mod. But that's just been my experience, someone with more expertise may have more of a success story to share.
From what I've gathered, the output tube tremolo that Doug uses in his AB763 circuit variation (refer to the 6G16 Vibroverb, and Doug's project: http://www.el34world.com/Hoffman/images/AB763Old.gif (http://www.el34world.com/Hoffman/images/AB763Old.gif)) apparently sounds way better and wouldn't suffer from the ticking common with the "roach" optocoupler tremolo. Haven't tried taking this route yet, but I'm getting there...
Anyways, I tried using a cap of the prescribed material that Fender suggested, I tried making the leads of the oscillator circuit very very short, lead dress, etc... I'm pretty convinced that with the roach trem circuit you'll just have to live with the ticking.
But hey, maybe someone else has a success story to share?
Good luck! - N
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I remember reading somewhere about adding a diode in the trem path somewhere to stop ticking. I will have to look at home with my notes and saved info and see though. I'll post later if I find it.
Greg