My Russound sdb-4.1 selector box suddenly stopped working - no sound can come through it. I had "A" speakers connected directly to front speaker outputs of receiver, and Russound "Amp A" wired to "B" speaker outputs of receiver. (It's a Pioneer VSX-1021k.) "B" speakers were then wired to output #1 of the Russound box. No other speakers are connected as of yet to the Russound unit. All worked fine for a week or so, and then suddenly the "B" speakers, thru the Russound, went silent. Receiver had "A+B" speakers properly set to on, and I am able to show the actual "B" speakers work correctly when I connect directly to receiver "B" outputs and take Russound unit out of the picture. I've tried reconnecting the Russound unit, hitting all button combinations, etc. Any thoughts? My problem is that I have a third set of speakers that I want to wire, and I need independent volume control for all 3 pairs of speakers, so a unit like the Russound is required. Thanks!