Preamp inputs - different quality

This may be a long shot, but is each input individually adjustable for gain? My Levinson preamp has this feature so that all inputs can be adjusted for uniform volume.
If so, it may be that the inferior sounding input simply is set a tad lower in gain, which we preceive as sounding veiled?

is it possible that there may be some oxidation in one of the input ? try cleaning with a tooth pick and cramolin, or the cleaner of your choice and see if the "sound" becomes uniform across all inputs.

Inputs are adjustable and set to the same level. Could be oxidation--I have not cleaned the terminals.

My ARC LS3-B has a multiple inputs but one is labeled direct input and activated with a toggle switch.It is better sounding.
George

bigamp, I had the same experience with a Krell KBL. I had been using input 1 but because of system rearranging it was moved to input 4 which was seldom used and it sounded different. Not sure if it was better but different. After some time it seemed to settle in and I didn't notice it any more. Could it be just some settling in time is needed for your ears?