I had the same problem with my Linn LP-12 Grado combination. If it is not a feedback issue, it can be as in my case a compliance mismatch with the tonearm and cartridge. I put on a new Shure V15vxmr and its 95% better!I have an article written by John Grado in the 70's that explains tonearm compliance further. It is kind of out there. I can fax it next week if you would like to read it.
driver moving too much
I have recently bought a turntable for my audio system. It is a music hall 2.1 and I have noticed that when playing some recordings the driver in my speakers moves a lot especially at high volume levels. Even when there is silence in the recording the driver moves without producing sound. I was wondering if anyone can tell me what causes this and if it is bad for my system in any way. ANy inputs will be appreciated.