gate signal to different speakers [solved]

I have multiple small speakers each with its own amplifier. I am trying to play sounds on one speaker at a time, which changes every few seconds, from a single sound-card. The trick is that I designed a nice stable power supply for good op-amps, amplifying the signal from a very expensive sound-card. So I'm trying to find a way to gate the signal without distorting it. Do you have suggestions on how to achieve that with an arduino? One idea I had was to gate the power toward the op-amps rather than gating the signal. I'm not sure that would be distortion-free though, which would defy the point of having a stable power supply. If I use the arduino to saturate transistors gating the +12 and -12V from the power supply toward the op-amp, would that work? Do you have other ideas?
Thanks a lot,

Gating the power is unlikely to work well, for several reasons. I would switch the low level audio using an analog multiplexer:

Ok, thanks.
Could I feed the analog switch output to an amplifier? The sound-card is low voltage, so I could amplify the signal after gating it, no?

The lower a signal level. the higher its possible distortion by crosstalk, noise etc.

If you encounter such problems with the multiplexed signal, add amplifiers to the signal inputs.

The sound-card is low voltage, so I could amplify the signal after gating it, no?

Yes, of course. Analog switches are (usually) designed for low-power signals.

You may need some "pull down" resistors to keep unconnected inputs/outputs from floating, which could cause a click or pop when it's switched-on. (See if you can find some audio-related application information for the chips you're considering... Audio can be tricky.)

And... You'll probably have to switch at the audio zero-crossings... If you switch amplifiers/speakers in the middle of a "wave" the speaker that's turned-off is going to jump back to it's neutral position and the speaker that's switched-on is going to jump inward or outward to the position where the 1st speaker was. And, you're probably going to hear a click or pop from both speakers.

A better solution might be short crossfade (maybe 100 milliseconds or more), but that would probably require more circuitry.

I wouldn't expect distortion to be a problem as long as your switches/de-multiplexers can handle AC (negative analog voltages). I'd be more worried about noise... AC power line noise, or other noise from the power supply, or switching noise when the chips switch.

Great. Thanks for all the replies.
I'll try an analog switch first. The speakers will play brief beeps or clicks every few seconds so switching speakers during a sound is not an issue.