I've been waiting a few months but now its finished, it can switch the audio from three PC sound cards and three sound modules (MT32, SC55 mk1, SC55 mk2) I went all out on this one and bought gold plated RCA jacks and gold plated RCA plugs even though I know gold plated doesn't really make much of a difference from normal metal/steel/tin plated. I made all the cables as well and everything works very well, I was going to buy a 3.5mm audio switch box on Ebay that looks like a bare bones PCB but I thought there's enough room in these old parallel switch boxes for another switch and this is the result.... try one for yourself the parallel switch boxes are cheap on Ebay and some have more than three inputs.