Why does my system now have shrill top end.

OP last commented saying he was going to swap the amp this weekend and if not that then look at ac.
This weekend could well be late tonight, we do not know his work schedule.
However if not the amp, I certainly hope he does not jump straight to ac possibilities without at least swapping speaker cables no matter how unlikely that scenario may be. Its cheap, quick and easy.
I am thinking the amp swap will reveal plenty but we just have to wait for now.

Thank you
Kevin

Thanks for all the great suggestions. I turned off all lights in the house and it made no change. For the HOI I changed the power cord from a PS Audio AC5 to the stock cord that came with the amp and although it had no effect on the upper registers it seemed to focus the sound stage more. I guess this is left for another discussion.

I wanted to switch amps but the 5 channel unit I use for the surround sound room is much too heavy for me to easily move. Hopefully I can get a friend to help me and will report back afterwards. I too think it must be the amp but this test will tell for sure.

I too think it must be the amp but this test will tell for sure.

Hopefully Kosst will take my response to this in the constructive spirit in which it is offered: If the problem goes away when the amp is changed, while it would substantially increase the likelihood that the Pass amp is the culprit, it would not by any means be a conclusive indication. It could simply be that the other amp is less sensitive to the effects of a speaker cable having very high capacitance.

Also, can you answer a couple of questions I had raised earlier:

1)What is the full model name of the Ortofon Black cartridge?

2)Do the OCOS cables have a "red" termination network, a "black" termination network, or neither.

Good luck. Regards,
-- Al

About a year ago I was experiencing system symptoms virtually identical to those the OP has described. At some point after much thought, frustration and experimentation, I replaced my speaker cables and the harshness disappeared. 

30 feet of Monster Cable or 12 gauge TW cable from the hardware store will be an easy and inexpensive experiment. Hope this helps.