Need Suggestions, have two extra toggles to use

[Ripthorn]

Hi guys, my tube preamp is almost done, but a couple of the features I originally planned on turned out to not work well, so now I come here for suggestions.  My preamp has a clean and dirty channel with switchable boost.  The tone stacks for each channel are different and each one can be disabled via a toggle switch.  Now I have either two spst or spdt toggles that are drilled for on the panel, but currently not being used.  I am trying to think of what I could do with them, but I'm coming up blank.  I tried making the tone stacks switchable, but that didn't work out so well.  Anyone have any good ideas?

[JOHNO]

perhaps a "bright" switch like on the fender bassman or vox AC30

[Ripthorn]

I forgot to mention that the boost has a lead/rhythm switch, but is not a bright switch per se.  That's not a bad idea, though.  Any other ideas?

[JOHNO]

you could switch the cathode bypass caps in and out.

[Mark Hammer]

I'm assuming here that your disabling of the tonestack is essentially a circuit bypass. Correct?

Fender/Marshall-style tonestacks are passive circuits that function by selective bleed.  When the bleeding is stemmed (i.e., the ground connection is open or a high resistance), the amount of passive signal loss is drastically reduced, and the amplitude of the signal hitting the next stage is substantially greater.

There was a nifty amp-mod article in POLYHONY years ago suggesting the lifting of the midrange connection to ground as a "boost".  I installed this on a blackface Tremoloux I had at the time and it worked like a charm, serving to both overdrive the next stage and also cancel the midrange scoop inherent to the circuit, making for a ballsier sound for solos.

The complete cancellation of all passive bleed may be more than some folks want or need, particularly since it renders much of the control of the tonestack much less functional.  Consequently, a 3-way toggle that inserted, say, no resistance, 22k resistance, or 100k resistance, between the midrange pot and ground, could serve as a nice mod to both alter the tone and add a little more drive potential.  Pretty simple mod with big returns.

It is also the sort of thing one can install a footswitch jack for in parallel for remote control.  I.E. set the resistance to ground at 100k, and use the footswitch to stick the resistance of your choice in parallel.

Another potential mod is a "shift" control for the mids and highs, that simultaneously switch the cap values for the treble and mid control.

[Ripthorn]

The disabling of the tonestack is a true bypass, correct.  The idea of changing the resistance to ground is a good idea.  Too bad my footswitch is already occupied (though I suppose I could do a second one or perhaps wire one up using some sort of multi-conductor cable).  One of the tonestacks is a James stack (passive Baxandall), so changing mid resistance to ground wouldn't work, but the other tonestack would work with that.  Hmm, things to think about.

Edit: Now that I think about it, I think my local electronics place carries dpdt switches that would fit in the holes as well, if that open up any further suggestions.

[Mark Hammer]

The tonestack doesn't NEED to be footswitchable.  I just figured that if it COULD be, there would be another option to consider.  Personally, I like it when amp controls provide me the option of using them with or without a footswitch.

[Ripthorn]

I love footswitchable stuff, too.  Luckily, I have space so that I could always put in another footswitch jack if I want (though keeping track of both might be tricky).  Maybe I put a bright switch with the bax and a mid-to-ground resistor on the dirty channel (for all my searing soloes on my 2W BEAST! ).