I recently purchased a new iMac and a Pioneer stereo receiver. Using either RCA cables or a TosLink optical cable, I can only hear sound out of one channel (left). I have checked the sound settings, don't worry, the balance is fine. What makes it bizzare is that I can plug any other speakers into my iMac and have no problems. On top of that, I can plug any other source (my ipod and my shuffle) into the receiver and have no problems there. Any ideas?