Taming a SF Champ tone stack bypass mod?

[Jborges]

Hey I was wondering if anyone could help me or make suggestions on some mods I did to a SF Champ. This is what I have done so far.

Build a new bigger pine Cab with a weber Alnico 1x12
Upgrade OT to a Allen T011c
Tone Stack Bypass - pretty much this to a DPDT Switch - http://blueguitar.org/new/schem/fend...aa764-mods.jpg

I have wired the tone stack like that picture. I have also seen a similar one with a 5m resistor wired across the 2 center lugs. Not sure if that is better or not.

I am trying to have the dpdt switch give me something close sounding to a 5f1.
Basically a aa764 and 5f1 in one amp approximately.
My problem is when the stack is bypassed it has that huge DB boost and the gain is a bit too much. It sounds good but is a bit over the top for my tastes. Is there a way to tame it down a bit? I know there will be a volume boost when you bypass the stack. I don't mind some boost, but it is pretty significant.

I am relatively new to this stuff so any help or even other mods suggestions are much appreciated.

[MWJB]

When you switch to 5F1 mode you get the additional gain of the 2nd stage bypass cap, which the 5F1 doesn't have. Convert to the 5F1 feedback loop, connecting the 22K to the top of the 1.5K cathode resistor & lose the 2nd stage bypass cap.

Or, make the 2nd stage bypass cap switchable in/out (bypass the switch with a 100K resistor) and reduce the vale of the 2.7K NFB resistor to closer to the 16:1NFB ratio (680-820ohms), compared to the 58:1 ratio that the SF has stock.

Unless you are going to have 3 or 4 switches, you will need to accept a compromise here & there.

By the way, a big dB boost is normal when bypassing the SF tone stack...You could also try a 5751 preamp tube if the stock 5F1 is too gainy, but this will affect the SF mode performance too.

[ThermionicScott]

How about wiring a big resistor (like 470k or 1M) in series before the 0.02uF cap so that it forms a lossy divider with the volume pot?

Otherwise, the boost in gain is to be expected, and is one of the main reasons people bypass the tone stack in the first place.

- Scott

[Jborges]

Thanks guys. I have been messing with the different variables above and had about settled on using a 3p3t and hook the 2ndstage bypass cap and tone stack lift to it. I ended up Trying out Scotts suggestion and I think that will work out well. You still get the nice gain boost , but it keeps it from getting too out of hand. I keep messing with the different options. Thanks again.