Hum from Grado on LP12.. Better carts to consider?


I've had a problem with hum on my LP12 for as long as I can remember. The table (bought used) came with a Grado Signature 8MZ and I've since tried a Grado Z+ that I had from another table. Both have the same amount of hum. I have a lot of RF and noisy AC in my house. The hum is noticeable when I switch to phono and gets louder as I move the cart over the rim of the platter. From there it decreases as I move the arm towards the spindle. (The table is 80's vintage with Ittok and Circus/Lingo upgrades).

A (non-Linn) dealer said 'oh Grados do that on LP12s - lack of shielding'. My Linn dealer didn't nave a strong opinion. He suggested a Benz Ace H given my under- $700 budget. From reading the Agon forums, some think an AT150 M series has better sound for less $. I've also heard good things about the Dynavector DV-20X. Does MM/MI vs. HOMC matter in terms of hum or is the degree of 'shielding' a variable from cartridge to cartridge no matter which type? Does a good review on a MC necessarily extend to the HO version, as opposed to the LO/MO versions?

My system: ARC PH1 (48 dB gain, variable loading via soldering iron)
ARC LS2BII
PSE Studio IV/V's
Audio Physic Tempo III's
FWIW: Meridian 508 CD player is dead quiet in this system.

Music: from Joni Mitchell to Ian Dury and the Blockheads, Monk to Mozart.

Thanks for any knowledge you can impart!
geor
Thanks everyone. Does anyone know how to attach a ground wire to a Linn motor? I'll ask my Linn 'mechanic' but I can already see the look on his face.
If the motor is made of a metal that can be soldered, then solder it. Otherwise a wire with a lug, placed under a nut and bolt should do the job.
A ground wire will NOT shield the motor and there will be no effect on the hum. Your Linn dealer will look at you funny for a reason, it will not work and maybe even create a ground loop which will make any cartridge you install hum. The only way to shield the motor is to isolate it, surround it with a magnetic shielding material.
Thanks Atmasphere and Snfrosten. I will take my LP12 to the Linn dealer and ask them to try it on their system. I'll keep you posted.