Is LP distortion the record or the cartridge?

Cartridge alignment is paramount.


If the LPs are damaged, there won't be anything you can do.

Sorry to report, distortion and mistracking are the bane of the vinyl universe. If possible, drag the turntable to a reputable dealer/tech and have them set it up. Or have 'em come by! If you decide to do it yourself, don't drink too much coffee before you attempt your own adjustments, You don't wanna have the shakes. And attach suitable magnifying lenses to your eyeballs.

I really only noticed this distortion after inserting my new Atma-Sphere MP-1. Could its sensitivity be part of the cause?
But my records are old and were played on a not so good TT before...
I did get Tri to help me on the phone with set up. Assume it is good.

you need a new reference disc in good shape and the inventor of your phono stage weighed in a few posts ago....

"the inventor of your phono stage weighed in a few posts ago...."

And was spot on...  "Cartridge alignment is paramount". 

When your system becomes more transparent (as in your case the addition of the MP-1), you'll hear some of the "sins" that were previously masked. The same thing happen to me when I changed from Tekton to Wilson speakers. In that case, I checked the cartridge alignment & found it off ever so slightly. Once fixed, the distortion problem went away.