Suggested upgrade paths

@joeycastillo that was my 1st thought to.. especially when he mentioned he didn't think the bass was punchy or good with volume up either. Like when you are really taxing an amp & the bass actually starts getting quieter as you turn up the volume. Clipping the amp would cause high frequency distortion. 

I assumed that the amp couldn't be the issue as I believe it's rated at 200 watts x 2. I've had a couple Rotel amps in the 90's & a 1582mkii I picked up awhile ago. I never noticed an issue but I probably never pushed them hard. Maybe the Super Lintons are tougher to drive or that amp just doesn't have the guts to provide it's specified wattage. 

Your assessment makes more sense but that's a shame if a 400 watt amp can't push a pair of bookshelves to loud volumes. 

@mattw73 

I agree with you as I believe that the amp being 200W has the drive capability. Not owning the Litton's BUT owning a few Rotel, I can only speculate at the power amp as a possible culprit. My Experience with the Rotels (Lacking power) was when I played large ensembles and when music that is being played has a lot of drums and low frequency Organ music, I did notice that vocals and treble became shrill BUT when I lower the volume, the shrillness disappears. The speakers I notice this anomaly where on LRS and ATC speakers. However, it does not seem to be apparent on B&W 

I stumble into the Fix when I got my Pass. All of the above speakers had NOT manifested the shrillness at all. it just plays LOUD and Clear. (a bit of disclosure, I don't listen loud unless I am doing some testing)

That is why I posted my observations on this thread. The OP may benefit on what I have encountered. a Sub is a good add on, so it makes the music bigger, fuller not needing to raise the volume, but it's not the fix

I also assume that the OP has the correct Power sources to supply the amps (good size power cords and clean power outlets) as that too can restrict power to the amps

@joeycastillo yeah after you shared your similar experiences I don't doubt that thé amp is the weak link in this situation. I think you hit the nail on the head. I was just initially surprised due to specs & their decent reputation. But that really means nothing lol. 

Can Op record the shrill sound and post it on YT?  It might make the remote diagnosis easier.

an amplifier change will do it, the unison research are hybrids with a tube front end, combined with a very punchy solid state amplifier. section.

also the subwoofer idea is also a good solution as the room is large and bass augmentation is always a nice improvement.

Dave and Troy

Audio Intellect NJ

Unison Research dealers