Switching bias on a bias-vary trem 6L6 Fender (e.g., 6G16, 6G11/A, etc.)

[seveneves]

Hi all,

I'm semi-interested in a 6G16 brown Vibroverb build. I've done a Super Reverb AB763 build about a dozen or so years ago so not a complete stranger to Fender builds.

But, I am learning that one of the big issues with bias-vary trem for the 6L6 based amps (e.g., 6G16, 6G11/A, etc.) is that the amp is either biased to have a great tone (hotter bias) or great trem (colder bias).

IOW, I can't "have my cake and eat it too", apparently... or can I?

Stupid idea/question but I was thinking to have a switch (DPDT) to toggle between cold and hot bias settings. Then, I could have my cake and eat it too?

I would most certainly be interested as to why this would be stupid/wouldn't work.

Thank you in advance.

[LOUDthud]

I would simply add a resistor (or make it a resistor and a trim pot) to ground from the output of the bias filter network with a switch between the resistor and ground. That way the output tubes never see a condition with no bias. If you were really clever, you could make it so the hotter bias is activated by the tremolo footswitch when the tremolo is switched off.

[Reeltarded]

A fairly low bias is your friend with brown amps.

Overbiased Fenders. Yuck.

[seveneves]

I would simply add a resistor (or make it a resistor and a trim pot) to ground from the output of the bias filter network with a switch between the resistor and ground. That way the output tubes never see a condition with no bias. If you were really clever, you could make it so the hotter bias is activated by the tremolo footswitch when the tremolo is switched off.

Cool. Thanks for that.

Would a shorting type toggle switch help?

[seveneves]

I would simply add a resistor (or make it a resistor and a trim pot) to ground from the output of the bias filter network with a switch between the resistor and ground. That way the output tubes never see a condition with no bias. If you were really clever, you could make it so the hotter bias is activated by the tremolo footswitch when the tremolo is switched off.

A picture = 1k words.

Am I on the right track here?

[LOUDthud]

That would work except you might get a loud thump when you throw the switch. Leave one resistor connected all the time, then connect the second resistor for hotter bias.

[seveneves]

OK. Do you mean the second resistor switched in parallel?