Hi, I have a Yamaha RX-V657 receiver, with a center channel, front left+right, surround left+right and sub hooked up.
When I watch DTS or Dolby Digital movies the subwoofer does its thing, its awesome.
However, when I play music from my media center, which comes in as 2 channel stereo (PCM) over S/PDIF, the sub doesn't do anything.
If I put the amp in 'straight' mode, I only hear sound out of the front left+right speakers. However, if I put it in standard-surround, or 7-channel-stereo, then I hear music out of the surround speakers and the center channel, but not the sub.