Find the Problem

I think it may be your VTA. Try lowering the arm.

Mistracking.

Can we assume that the cartridge is also “newish”?  If so, and If you haven’t already, try increasing the tracking force to the upper end of the recommended range.  Of course, make sure the stylus is very clean.  Please report back.  Good luck. 

This problem isn’t present with my digital sources (Pioneer Universal player, television, even Apple TV playing old compressed iTunes files) .

Do you mean you don't have the issue on your main system, or that digital sources in the basement are unaffected? If the latter, we can rule out room effects.

Could be tinnitus.

Ototoxicity.

Doesn’t the AVR digitize the signal from the phono pre?  If so, maybe its the ADC that’s causing the problem. 

If it hardens in the same place regardless of volume it's the TT/Cartridge.  If it only hardens after turning the volume control to a certain point it's more likely to be the amp.

A dirty stylus can ruin a normally enjoyable LP experience. 

I have a technics tt as well, started out with a Pickering cartridge which had the harshness you were talking about. Then I went to the ortofon blue which made a huge difference, but what when I really noticed a difference was switching the headshell from plastic technics to the ortofon, going to the bronze cartridge, and proper positioning of the cartridge in the headshell. Also clean your LPs get all the dust and debris out. 

How many hours do you have on the stylus?  Have you used a test record to verify your setup?

The digital sources in the system that has the turntable, my basement system, do not show this problem.  I believe that narrows the issue down to the turntable, arm, cartridge/stylus, phono pre amp, or perhaps the LPs.

  I have hardly listened to the analog system for the last 2 months, primarily because we were out of town caring for my mother in law who was in hospice at home.  I don’t recall noticing the problem previously.

  Regarding the cartridge alignment, why would that only cause an issue during the loudest passages?  I had purchased the table from Music Direct in Chicago and had them mount the cartridge.  I don’t have the tools to do an alignment and it’s been half a century since I’ve done this, and frankly I don’t trust my eyesight to much at this point to detect a minor misalignment.  I have another dealer 20 miles away who will check it if I bring it in, and I might do that, but as a last resort.

  The record that really made me notice this (Jascha Horenstein/London Symphony Orchestra in Mahler Third Symphony) hasn’t gotten the deluxe cleaning treatment.  I have my LPs cleaned by a local guy with an Ultrasound machine who gives a bulk discount.  I am waiting to take possession of some LPs that my in laws possessed and have him do the lot so that might take several weeks.  I’ll spin some other cleaner LPs in the interim 

I went through the problem of harshness on sopranos and forceful brass recently and discovered the problem was dirty power.

I had a 30-year old power conditioner on the line and thought I had no problems caused by power.  Then I borrowed a modern power conditioner from my dealer and was pleasantly surprised to find the harshness went away.  I actually tried three different new power conditioners before I found the one that totally eliminated the harshness.

Interesting.  I played a few albums today that I have had cleaned with Ultrasound, all with lots of treble and orchestral climaxes.  No problems.

Dirty power, dirty records, dirty stylus. Something is dirty, or all of those.

I personally used to have this from time to time, the cause was dirty power.

Maybe if you bought a new puppy it would change things

I’m allergic to dogs.  Not sure how sneezing all over the ls would make them sound better