I built these boxes to try and get some real A / B testing of amps and dacs done. This way, I only need another person to do initial connection of cables.
The first switch uses a DPDT switch, speaker wire, and a radio shack enclosure. I read in a guide from the net that wiring all of the grounds together would be fine, but found it to really screw up the output. I originally wired both input grounds to the output ground. I've now rewired it so that each ground has it's own wire, and they meet at the ends. This is the specific pattern from the guide, but I don't expect it will be functionally different, so I built another.
The second switch uses a 3PDT switch, speaker wire, and a decorative wooden box. The new switch lets the ground lines connect individually, so there is no physical interaction between components from each input. Drilling the recessed holes to mount the jacks on the inside was a nightmare, but well worth it.
Edited by morph2k4 - 10/13/13 at 4:21am