This isn't about the 975 but rather my 990 (SN 9900 10051910) which up to now has given flawless service for going on seven years. But now there is sound only in the left channel in all modes except BYPASS (no digital), where there is normal sound in both stereo channels. The problem happened quite suddenly a few days ago and suggests to me that the failure is in the digital processing.
At six years nine months old my unit is out of warranty, but if the problem could be cured by replacement of one circuit board I might be able to do it, since I have assembled home kits (Heath and Dyna)back in previous generations.