Hum Problem with Grado

I have a similar problem with a Grado Black on a new Rega Planar 3 - the hum really appears as the cartridge end of the tonearm reaches the end of the record - within 4-5" of the spindle.

I turned off the motor and moved the tonearm (not touching the platter) over the spindle, and there was no hum - but with the motor on, the hum appears as the headshell approaches the spindle and gets worse when I move the headshell right over the spindle.

So maybe this points to motor vibration being source of the hum, since the motor is on the side away from the tonearm and as the cartridge approaches the spindle it is always getting closer to the motor. Although in this situation, there is no contact with the LP or platter, so the vibrations would have to be transmitted through the air.

Can anyone advise, do the Rega upgrade kits that include vibration damping mounts help this situation? Do other cartridges have the same degree of problem?

Cserbell,
In your case, it was not caused by motor vibration. It was caused by the electric magnetic field generated by the motor since the Rega placed its motor under the platter near the center. You may try to reduce the hum by lining the underside of the platter with one or two layers of mu-matel sheet. Mu-matel can be cut in shape with a utility knife and can be mounted with double-sided tape. But they have very sharp edges (guess how I know). So handle with care.

Cserbell,
Good detective work, but the hum is not caused by physical vibration of the motor. It's caused by leakage of electromagnetic energy from the AC motor coils. EM energy travels through air pretty readily. That's why radio works.

Most cartridges are electrically shielded aginst EMI. Grado's are not, and are thus famous for humming. If you search here or on Vinyl Asylum for "grado + hum" you'll get a million hits. If you search for "most other cartridge names + hum" you'll get far fewer.

Possible solutions:
- shield the motor, try wrapping some foil around it
- shield the Grado, as mentioned by Ramstl
- dump the Grado

I recently bought my VPI Scout and set it up with a Grado Red just to get me going. I noticed a hum but only after a rather loud listening session where I left the volume way up and went to change a record. I was only a few feet from my speakers and noticed it. Turning the volume way up increases the hum...but I would never even consider listening at those levels. I tried grounding the table to pre-amp, less humm. I switched from my Kimber Hero's to AQ Diamondbacks and got even less hum, but sound was not as good.

Right now I still get an audible hum at high volumes when I am close to the speakers. Normal listening is ok. I'm sure it degrades the sound some and because of this will more than likely change to a new cartridge sooner than I thought.

Same problem for me with my VPI M4 and high output Grado Sonata. Not a huge hum, but motor induced and noticable at high volume levels. I shielded the motor assembly with two layers of mu metal and the hum is pretty much completely gone, I'd say 90% reduced. I could only hear the hum on the last three inches towards the spindle when not actually playing. But you know it's there. Easy to do and effective. A very good tweak for me because the cartridge wasn't cheap. Good listening.

http://www.lessemf.com/mag-shld.html