Perhaps completely unrelated, but my Clearaudio Symphony cartridge (VPI TT) paired with the 9200 may be requiring a separate phono stage w/ gain adjustment. I wouldn't have thought so, using the hi-gain setting with this 0.7 output, but it presents a buzzing sound that increases with volume that isn't there using low gain with a previous Clearaudio Aurum cartridge or (as a check) with the Symphony at low gain. Checked about every other possible source of that noise. Wasn't present in any combo other than the TT and amp.
At this point, it could also just be a problem with the amp. I'm going to be hooking up a separate phono stage w/ adjustable gain in the next few days to see if indeed that solves the problem.