Help -- my system is too bright

I appreciate the interesting feedback.

The old amp was an anthem MCA-50, which I still use
for the Center and Surrounds. It was a nice mellow amp, but not as detailed or extended as the Krell. I bought the Krell used, so I'm assuming it was broken in by the previous owner, but it may need more break-
in time. I am using a Proceed AVP2 pre-amp and a Yamaha s2300 Universal Player.

Does "digital hash" or noisy AC cause high end brightness?

Your system may now be so good that it's revealing how many bad recordings there are. After all, that is your system's "job-1". It's amusing when someone suggest using this-or-that tweek to make the sound "warmer" or whatever.
If a recording sounds bad either accept it or find a better one.

The Yamaha is not a good choice with the Krell, It is, as all universal players are: A little to universal sounding and your Krell can reveal poor upstream source with ease. I have two Krell amps and went through the same thing.

Now, this brings up another point. Already, some posters are counseling cable and power cord adjustments to give this system ___. This, IMO, is how people get
duped into blowing a lot of unneccessary money on cables.
Cables will not produce ___ in speakers that are not built to accomodate it.

This the Krell sound that I also experienced - hyperdetailed. I SHOULD have experimented with various cabling & tweaks before selling the amp for something different, but I *thought* that I knew better. I didn't listen though & now I wish that I had. Because that *next* amp, while not sounding hyperdetailed, exhibited some other issues, as did the next one & the one following that.
Possibly a different amp (but only possibly) yours may synergise better when everything else is tweaked in. I would approach the fine tuning issues by trying & applying some tweaks instead.
Here are some possible examples:
cones under your speakers
Speaker cables.
Interconnects.
Upgrade AC cords.
AC line conditioning.
Shelving.
Cones.
Footers & Pods.

If you have tried the Cardas Golden Reference interconnects but you still get the harshness and/or brightness then you should consider Shunyata Black Mamba or Python power cord and need to use Black Diamond Racing shelves or cones to eliminate the brightness. Good luck.