Distortion as note fades out.

[TomCarlos]

Check the Headphone jack, to make sure there is a solid connection on the sleeves. If these are dirty or not making proper contact, it could affect the output.

And while the PC board is out, check the solder joints. Lyle at Psionic Audio has a short video on this amp. He does a repair on the plus and minus 16 volt rails and the headphone jack.

https://www.youtube.com/watch?v=KzwhY8mWeSQ