I'm trying to build a really simple passive summing circuit for combining two line-level stereo audio sources (iPod + laptop or iPod + iPod), and I really want to be able to fade between the sources.
Basically, this would be between the audio source and the "tape input" on a PA.
I'm considering a dual gang slide potentiometer -- would that be enough, as long as I converted the stereo signals to mono first?
What about using a replacement crossfader from a DJ mixer? I imagine a lot of them are proprietary to a specific mixer, but are there any that I could just drop into a passive circuit?