rega p2 hum

[mpmarino]

I have a rega p2 (the NAD one) and I'm bothered by hum. It is fitted with a Linn Basik Plus arm and a Grado Black. I have tried a few pre/riaa stages and the symptoms stick. This is at med to high volume only and seems to be a 60Hz hum.

This hum is induced when the cartridge is in proximity of the motor. I've removed the arm and used it like a wand to prove that the internal arm wiring isn't shorting as I swing the arm. It's definitely a proximity issue. I've tried the arm grounded and not...no help.

Could I have issue with the motor? There is a board with a cap and resistor...could that be bad? What does it do? Geez, there is nothing to this thing!

I'm at a loss. I've actually considered putting MU metal under the platter but I'd rather not

please suggest

Thanks,
Marc

[jeff spall]

Hi Marc
The Grados are really great cartridges, but they do have a reputation, especially amongst Garrard owners, for being very susceptible to picking up hum. Having said that, I've used Grado-based cartridges for years (even on a 401) without a problem. I think that bit of gold metal stuff they wrap round them is for more than show!

A cople of toughts:

Assuming the hum's always been there rather than just appeared, maybe you have to take some steps to make sure it's well shielded. First I'd check that the original arm ground is working OK - I think earth grounding for an arm is really important. It might be worth taking an earth connection right up to the headshell.

Perhaps a bit of motor and electrics shielding? - like even some grounded aliuminium foil, nerdy by effective!

regards, Jeff

[mpmarino]

Thanks Jeff,

I recvd the table minus arm and the arm from two different sources. I have had the hum since I put it together... that's all I can say 'bout that.

I have tried a seperate earth and pre ground directly to the arm...not a lick of difference.

Maybe if I stuff the alu foil in my ears

Thanks for the reply

[jeff spall]

Hi, well, I have a p2 and a Grado cartridge around, so I'll put the two together tommorow and see if they hum. If they do , I gues you gotta shield the motor, If not, there must be a fault.

regards, jeff

[mpmarino]

That would be going above and beyond....and appreciated!

Thanks Jeff!

[tubenut]

Grado's are very susceptible to hum and the problem you describe is a common Rega/Grado ailment. (The non metal platter offering no shielding from the motor could be the reason for other TTs with metal platters not giving the problem.)
I am afraid that changing the Grado is gonna be your best bet....

Sorry to bear bad news....

[mpmarino]

Thanks tubenut,

It's OK...I can take it The Grado was cheap anyway.

[maxro]

Maybe you could run a sheet of mu metal between the glass platter and the mat. Or just shield the motor itself with mu metal.

Max