Hum on my turntable

Hum on my tutable

When the motor is on I get a hum on my turntable that increases the closer the tonearm gets to the center of the record.

Equipment:
Project Phono Box
Project RM-4 Turntable
Grado Gold

HK 2.0 Preamp
HK 2.1 Amp

Is this inherent in this set-up, or is there something I can do about it.

The hum goes away IMMEDIATELY when the motor is turned off. I've tried plugging them into the same outlets, different outlets, etc. I think it's in the tonearm.

-Tom

 

I've read that Grados can be sensitive to noise/interference coming from the motor. I think it may be electromagnetic in nature, not vibration. You may have to get another cart or somehow shield the motor. I saw an article where they did that with MuMetal (I believe).

P.S. "Hum on my tutable" reads vaguely suggestive. But so did "How do I know if I've blown my speaker?", so it could just be me. I'm a twisted pair.

 

More details

1)This is a new set up for me, had it maybe 40 days, but very little listening time.

2)It's is not my speakers for sure.

3)There is a hum from my speakers that IS volume dependent when I have the turntable on, the TT preamp on and the Main Preamp and the tonearm is over the platter. The closer I get to the motor the louder the hum is.

Maybe some sort of shielding is what I need, I jsut want to make sure it's not a defective cartridge or tonearm.

I'd lvoe to see the shielding article.

-Tom

 

I could not afford the MuMetal (I think) electromagnetic shielding for my huge tweeter that turned my TV green - So I added a piece of steel between the tweeter and the TV and it works.

Just think that PCs use steel chassis for EMI shielding so of course it would work. The MuMetal is like $15 a square foot and the steel is available at the local hardware store for a few $$.

You could cut two pieces in like a "C" shape and then insert them on top of the motor from both sides. Make sure it goes past the point towards the tonearm where it starts to hum.

I will post the link to buy the expensive shielding if I find the link.

 

Here is a link where you can buy MuMetal for $18.95 a linear foot 16" wide.
http://www.lessemf.com/wiring.html

I just found it on Google so I can not vouch for the company.

 

Re: Hum on my tutable

This is not that unusual, and others describe the problem exactly as you have. Contact the turntable manufacturer or your dealer for a recommended course of action. A different cartridge would surely work, but there could be a shielding solution as others suggest.

Regards,
Geoff

 

Be sure everything is grounded to the same ground. I am not familiar with your TT, does it have an outboard motor. The motor, the tonearm, the spindle and the phono preamp should all be grounded to the same ground and it should be a good ground connection to earth.