Pop suppression on switch

[miltown]

I have built a control unit/footswitch for a Leslile cabinet. The unit has an op-amp. I have a DPDT stomp switch that kills power to the op-amp and also switches inputs so that an external amp can be plugged into the cabinet. When I switch from op-amp off to on there is a pop. On the power side of the sw there is one lead that is open and I have read that I need a cap or resistor that would help to suppress the pop. So which do I choose and how do I size the component. Or if anyone has an idea for a suppression circuit let me know. Thanks

paul

[jrfrond]

Substitute a very high value resistor like 5M or greater for the open circuit to somewhat equalize the potential on both sides of the switch. 10M is pretty common in this application.

[J M Fahey]

The above solution is fine for the *audio* switching but turning *power* on and off while playing is usually bad engineering practice.
Leave it always on (power consumption is nil).
When you turn an amplifier on and off voltages take a certain finite time to stabilize; or, seeing it in other way, amps become "stupid" for a fraction of time, when turned on and off.
The resulting transients are heard as pops or thumps.

[miltown]

So just switch the inputs then, I'll take is what your saying. I can see that there really is no reason to turn the amp off .

[J M Fahey]

Look at what effects pedals do !!
They *are* meant to be switched, so much so that they *live* in a small box with a big footwsitch on top
And they switch signal only; power is turned on by plugging a guitar cord in most cases , and "wastefully" leaving them on for all of the show, even if battery powered.
Anyway apply what JRFrondelli suggested, which is placing high value resistors from each side of the audio switch to ground, to discharge any eventual small DC voltage on capacitors which would be heard as a click (rather than a more serious thump, which usually appears when switching power on and off).

[soundguruman]

The op amp should be on all the time, with a different switching configuration, that accomplishes the same thing.
You can't expect the output of the op amp to remain at 0 / silence, when you are flipping the power on and off.
But you could certainly switch the amp in out of circuit while it is turned on, or make a unity feedback loop to shut down the gain of the amp.
Wasting power of a battery whatever, you need to rethink your power scheme.