Someone with a L75........
Sold mine 25 years ago, so I can not replicate the problem. Anyway, you had a ground loop of some sort, and removing the ground on the TT may be the second best approach.
Best would be to find out why, but that takes time and effort, and can be maddening. Culprit may have been a cap from the AC line to the chassis. They can inject noise in a system. Which is why one might be best to use "medical grade" filters, if anyone is in the market for one. They do not use the problematic caps that can cause the problem.
Jensen Transformers have some interesting papers on that subject. You can find them on their webiste. Good reading.
Sold mine 25 years ago, so I can not replicate the problem. Anyway, you had a ground loop of some sort, and removing the ground on the TT may be the second best approach.
Best would be to find out why, but that takes time and effort, and can be maddening. Culprit may have been a cap from the AC line to the chassis. They can inject noise in a system. Which is why one might be best to use "medical grade" filters, if anyone is in the market for one. They do not use the problematic caps that can cause the problem.
Jensen Transformers have some interesting papers on that subject. You can find them on their webiste. Good reading.