Why does my system now have shrill top end.

Will swap the Amp this weekend. If no change I will start looking at AC issues.

To the OP
Did you try replacing the speaker cables yet? Anything will do for a cheap dirty test, zip cord, bell wire even regular SO cord ( no you do not have to use all 3 conductors LoL!).

I may have missed this but did this start at the same time as the kitchen refurb grand opening ceremony? If not then even though all the potential kitchen issues may not be helping overall SQ I doubt that it is the cause of this particular gremlin.
I am thinking most likely cause (after eliminating speaker cables and checking all interconnect integrity) would be the Pass or the P5 but most likely the Pass.
Hoping it is not as yes it is a royal pain and cost to pack up and ship back to Pass for a checkup.

On another note entirely (sic)
Why oh why do we feel the need for openly hostile, rude, antagonistic and generally arrogant posts? Oh and then the additional purely inane ones to boot that serve no usefull purpose whatsoever.
Everybody is a keyboard warrior nowadays........

Jim (Jea48), in my case there's no particular reason I haven't mentioned the preamp.  It's certainly one of many possibilities that can't be ruled out at this point.

Also, +1 to all of the comments by Uberwaltz.

Best regards,
-- Al
 

The cables seem highly unlikely, based on the info provided for a multitude of reasons. It is sudden, it's on both channels and proacman didn't mention messing with cables at all.