Cathode Bias Switching for a Bias Vary Tremolo Amp?

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4/25/2003 11:03 AM

Deltablues

Cathode Bias Switching for a Bias Vary Tremolo Amp? Does anyone know of a mod for Cathode Bias Switching that can be used on an amp that has bias vary tremolo? (e.g. the common "London Power" mod uses a "bias balance" setup and only works with opto-roach tremolo amps. If it's used on a bias vary tremolo amp, the London Power mod requires disabling the tremolo, which I don't want to do).     This is for a Fender 6G16 (brown vibroverb clone) amp.     I've heard that "Sal Trentino" has a patented mod for cathode bias switching that "might" work, but I haven't had any luck finding his mod or getting him to answer emails about how his works...?

 

4/27/2003 12:35 PM
Deltablues	Anyone...?

 

4/29/2003 1:25 AM

Tim Gagan

Larry,   Are you talking about switching between grid bias and cathode bias, and keeping that tremelo circuit active? I've built a couple of cathode bias amps with the bias-vary tremelo circuit. What happens with the intensity pot is the leg that's connected to the bias voltage in the Vibroverb gets grounded in a cathode biased amp. So it seems to me that you'd just need a dpdt switch. Here's a diagram of how I think it should work, if I understand what you're asking:   http://www.gaganbros.com/images/kbiastremeloswitch.bmp   Tim

 

4/29/2003 3:23 AM
Chandler	I used the mod in TUT2(3-21)for my Brown deluxe clone. Good Luck, Chandler

 

4/30/2003 6:30 PM
Deltablues	Tim:     Wouldn't that mod simply allow you to have tremolo while in fixed bias mode and to have cathode bias mode without tremolo? (That's what I'm trying to resolve). I want to be able to have the tremolo working no matter if I'm in cathode or fixed bias mode.     Chandler:     What is: "TUT2(3-21)"

 

4/30/2003 5:10 PM
jason	quote: "What is: "TUT2"     The Ultimate Tone volume 2 by Kevin O'Connor.     jason

 

4/30/2003 7:34 PM

Deltablues

Kevin O'Connor was actually the one that pointed out that the mod in question can't be "completely" done if you want to retain your tremolo.     "One consideration that is not critical for every player, or on every amp, is whether a tremolo feature is present (and used). If a tremolo is used, then we must not disable the fixed-bias supply completely, as it is tied into the tremolo as a "mute" control. In this case, we simply want to disconnect the bias supply from the output stage when cathode-bias is desired."     Chandler: Does your Brown Deluxe tremolo work when you have it in Cathode Bias mode?

 

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