Little update here on the Nobsound passive 4-1 mixers...I got some email back from Nobsound, and while I didn't get any feedback on whether or not these can pass DC, the designer says that these LOVE higher voltages...you can safely pump 10VRMS thru 'em and they'll be happy as a clam! So at the very least, they'll function admirably as drop-ins for audio paths.