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Hum in an Suminko Project RM-4 Turntable.

I hope somebody has some knowledge to help me out. In my second rig I have an Project RM-4 turntable with a Grado Prestige Gold Cartridge. The turntable sounds very good but it has an small but audible hum. It not caused by a ground. Ive got it grounded six ways to Sunday.

Could it be the Grado Cartridge, I've heard rumors that they are susceptible to motor noise, especially if the motor is mounted within the plinth. Is this true, or just some blarney started by one of Grado's competitors.
walkertm

Showing 1 response by newbee

newbee
4,751 posts
 
It is true. I have a Grado and use it in an Oracle TT/MMT arm combo - the motor is shielded, no hum! Same cartridge used in a Mission TT, same arm, with unshielded motor - when the cartridge is on the outside edge of an LP hum is minimal but as it moves toward the center where the motor is the hum increases and becomes fairly noticible.

It is possible to jerry rig shielding of the TT's motor (which I've never done) but it is just easier to get a different cartridge which is shielded.
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