Stumped

What would cause my cd to play at very low volume even with the amplifier volume knob at 12 o'clock, while my phono played at a level appropriate for that volume setting?

When I turned off the amp and sources to alternate ICs from one input to another, on restart levels were equal. Turned off amp and returned ICs to original inputs. Started up again and everything was fine and has been since.

The amp is a Cary SLI-80. All tubes are new. ICs are clean and tight. On initial start up I didn't allow much time for the amp to warm, but would that cause the volume to fluctuate from source to source?

Thanks for any insight.