Stereo volume control with a single pot

[IO390]

I'm rebuilding my amp, and out of interest I began to wonder if there's any practical (analogue) way of attenuating two separate signals using a single pot.

I played with a few circuits that just attenuated the signal using a transistor as the bottom half of a voltage divider, but it didn't really work. So yeah, can anyone think of anything?

[grumpydoc]

You could just use a single pot as a voltage divider, then drive the control voltage of a pair of VCAs, or perhaps digital pots but I can't quite see the advantage.

[Richard Crowley]

I'm rebuilding my amp, and out of interest I began to wonder if there's any practical (analogue) way of attenuating two separate signals using a single pot.

Clearly you can't DIRECTLY attenuate two different signals with a single pot.  So you must use the pot to control two (or more) separate voltage-controlled amplifiers or attenuators.

I played with a few circuits that just attenuated the signal using a transistor as the bottom half of a voltage divider, but it didn't really work.

What does "didn't really work" mean exactly?  That leaves us with far more questions than it purports to answer.  Do you mean you couldn't get the attenuation range you need (which is also not revealed here)?  Or do you mean the performance (IM distortion, noise ratio, or whatever) didn't meet your requirements (also not revealed)?

In any case attempting to use a single pot (especially if it is the original log-taper pot) to control stereo signals will be far more extrordinarily challenging to do than simply replacing the single-section pot with a dual ("stereo") pot.  Is there some overwhelming reason why you can't simply replace the pot?