Multiple Drive Pots, 1 effect?

[GibsonGM]

Hi,

I'm having ideas about pre-setting an overdrive rhythm sound and a very high gain lead sound using the same distortion ckt - same as just turning the drive control, but it would be stomp-switched between 2 pots coming off the gain loop of an OA.  Does anyone know if the different voltages between the pots in that part of a gain control would cause huge popping when going back & forth?  And if so, what to do to minimize it?
Thanks, I think this idea has some potential... 

[Mark Hammer]

It can work in pop free manner.  The easiest way to do it is to use the ground leg and have two pots in series, wired up as variable resistors.  A SPDT switch (or DPDT if you want status LEDs) can be used.  The common lug of the switch goes to the junction of the two pots, and each outside lug of the switch goes to the "far" side of one of the pots.  Step once, and Pot 1 gets shunted, making Pot 2 set the resistance and gain.  Step again, and the switch now shunts pot 2, making Pot 1 set the resistance to ground and gain.

The odds of this producing pops are much less than the odds of popping should you decide to set gain via a feedback resistor. Why?  Because during that VERY brief instant when neither Pot 1 or Pot 2 is being shunted, their series resistance is higher.  In the feedback loop, that increased resistance momentarily sets the gain much higher.  In the ground leg, a higher series resistance decreases gain.

I've used this method successfully with fixed resistors, where a switch selects between two gain settings via the ground leg resistance.  At the same time, I switched a resistor in series with the output pot in and out of circuit so that volume level stayed constant even though drive was changed.  When the drive was goosed on the gain stage, a resistor was added i series with the volume pot, effectively decreasing volume.  When the drive got reduced, the series resistor on the volume pot was shunted, eliminating that preset attenuation.  Worked like a charm

[GibsonGM]

Hey, good call, Mark! Thank you.  Makes infinitely more sense than fiddling with ground switching, and uses a simpler (cheaper) switch!