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

[fazeka]

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.

[sluckey]

Should work.

[fazeka]

Should work.

Hi Steve,

Thanks.

Was hoping to use the ground switch position to do this. Any issue with the leads running there?

Also, would your LED trem mod help in this regard as far as the 6G16 trem is concerned?

[sluckey]

No problems using the ground switch. The LED will definitely help. Do that first. You may not need the bias switch.

[fazeka]

OK!

Assuming it would look something like this?



Is it better to use a shorting switch or does it even matter? I believe the stock Fender (Carling) ground switch is non-shorting?

[tubeswell]

You can get great bias-vary trem AND great tone with 6L6s if you set the LFO up with decent current buffer. A MOSFET source follower using an IRF820 is ideal for this.

[fazeka]

You can get great bias-vary trem AND great tone with 6L6s if you set the LFO up with decent current buffer. A MOSFET source follower using an IRF820 is ideal for this.

Where can I get more info on implementing this into my build?

[sluckey]

Is it better to use a shorting switch or does it even matter?

Doesn't matter.

[sluckey]

Where can I get more info on implementing this into my build?

6G16 already has a current buffer.

[Esquirefreak]

The 6G9-B I owned had the best bias trem I've heard. I think that both the colder bias (37mA) and the lower B+ (roughly 400vdc) contributes to that.

A very deep and bold tremolo. No "thumping" in that amp

/Max

[tubeswell]

You can get great bias-vary trem AND great tone with 6L6s if you set the LFO up with decent current buffer. A MOSFET source follower using an IRF820 is ideal for this.

Where can I get more info on implementing this into my build?

Here's one I did about 10 years ago. Trem works like a charm

[fazeka]

Here's one I did about 10 years ago. Trem works like a charm

Thank you!

[sluckey]

6G16 already has a current buffer.

[fazeka]

6G16 already has a current buffer.

It appears you are emphasizing this for a reason. Cool.

I'd be interested in how this translates to the build that I am planning. Is there a mod of some kind involved or are you saying that none is needed because the original design is already adequate?

Apologies that's it's not clear to me which of the two it is (or if it's something else completely different) and that I'm not tracking what you're trying to get at; I'm a newbie still trying to learn a lot.

Thanks for your time, patience and understanding.

[sluckey]

... are you saying that none is needed because the original design is already adequate?

BINGO!

Tubeswell's trem circuit is identical to the stock 6G16, except he replaced the tube cathode follower with a MOSFET source follower. Still gonna have the same issues driving 6L6s.