Hum Issues - Rega P-25 w/ Grado Reference Platnum


My friend just put a Grado Reference Platinum cartridge on his Rega P-25. As the cartridge tracks toward the center of the records, the hum increases from non-existant to unacceptable.

Is there anything that can be done about this?

Is it possible to put some type of shielding between the motor and the platter? Or perhaps coat the underside of the platter with a copper-based paint to shield the cart from the inductive interference from the motor?

Has anyone else experienced this?

Thoughts?
128x128nrenter
I'm surprised that TAS didn't title the following article "Two great tastes that *don't* taste great together."

Affordable Gear from Two Veteran Companies

From what is implied in this article, and if I didn't know better, a Rega / Grado combo would be a *huge* bang for the buck. Note that they don't talk about the synergy of the two together.

I'll back Jim up on the sound of his combo (especially with the RB-1000 arm)...it sounds great and is getting better over time (his cartridge is out-of-the-box brand spankin' new). But if this problem is well known, someone *has* to have a tweak / mod to address this issue.

Jim, maybe you should fire off an e-mail to Rega.
Here's more info on one solution that was recommended above:

Well, here is one from the archive : (for Rega 2/3, from an article in Audio 1998 by Cory Greenberg)

The material used comes from Magnetic Shield Corporation and is called Mu-Metal. There is a lab kit that contains several sheets for $80, CO-NETIC AA for low intensity fields and NETIC for high intensity fields.

Shielding the motor with the NETIC didn't work so he tried placing the CO-NETIC sheets on the base under the platter, and this did it.

He recommends is to remove the cart from the arm and the glass outer platter and plastic inner spindle from the turntable. Be careful when cutting the hole for the bearing, because the sheets can bend and may scrape the underside of the plastic inner spindle. Fix it with double-sided tape. If you don't like the color, you an paint it without changing it's shielding properties.

One can buy directly from the company 630/766-7800; ask for product LK-110.

This was pulled from an AA archive.
Hello,

Your problem is normal with your grado cartridge because it is not protected against the magnetic and electric fields from the motor. You have two solutions. First, put a metal cover under the turntable between the motor and the plinth. Finnally, change your cartridge and choose one which is well protected against the magnetic and electric fields. An example, the rega Elys or the old Linn K9.