Pass X150.5 vs. X250.5

You might also look into your AC power. Is your Amp plugged into a dedicated line?

Update to the problem. As hard as it is to believe, I changed the power going to my pre-amp from a conditioner that had my digital front end plugged into it to one that only had an analog device plugged into it and the harshness was almost completely eliminated. This even though the MFR said the outlets were isolated. Then tried heavy curtains on part of back wall, but that made things too dull, so guess I'll live with the considerable improvement the conditioner switch gave me, until I can get some diffusion for the back wall and try that. Thanks to all! And keep the ideas coming.

Plug your amp right into the wall, and forget the conditioner.

I agree with Swanny. Amps directly into wall.

Ccanino, My Equitech unit has isolated and separate plugs for digital and analog and I still unplug my digital when I spin LPs.

Seems like separate is absolutely the way to go as far as power is concerned. Just wish it would be easier to get a dedicated line into the room, but there is no floor access to the main panel as there is a slab floor. Ceiling is floor to second level. Like I said though , major improvement with separate power sources!