Grounding problem: I'm clueless

Grado Prestige Gold is unshielded cartridge. Unfortunately with DD turntable always to hear hum.
Sorry for my poor english.

Zenek is correct. A few years back, Stereophile magazine had an article which described applying sheets of magnetic sheilding to the plinthe of the turntable (I beleive the TT they were sheilding to be a Rega) which solved the problem well, but may not result in the best cosmetic appearance. They also gave information on just where to buy the sheilding material which was sticky on one side. FWIW, I hope this helps. Someone out there may have more info on which issue addressed this problem with Grado cartridges.

Are you sure the phono stage doesn't need to be re-tubed?

A couple of things to try -

ISOLATE THE CAUSE: Remove the TT from the system with the phono stage still in line and see if the hum is still there.
If so - you know the problem is related to the Phono Stage.
If not - Remove the phono stage and connect the TT directly through to the preamp, turn it on, and see if the hum is coming from the TT.

If no hum from the TT either (with preamp volume at Max.) then you know the issue is the relationship between the TT and Phono Stage.

If the power plugs on either the TT, PS, or Preamp are the old 2-prong, non-polarized type (both prongs the same size), try different combinations of flipping them over in the outlet (reversing the polarity). With 3 non-polarized plugs there should be 6 possible combinations - only 1 of which is really "polarity correct".

Keep in mind when running external ground wires that the chassis/case of any equipment with a 2-prong, non-polarized plug is NOT a valid ground point. It is totally isolated from the electronics within. Running a ground a wire from/to the chassis of any such equipment is the same as trying to ground a turntable to an armchair.

Hope this helps.

YOu have somje RFI if you can hear radio through your system. Some Phono stages are prone to this. The 47Labs is one in particular. Where are you hookig the ground/drain wire to on your turntable?

Hi folks, thanks for the advice.

Opalchip, I just tried to isolate the cause as you suggested. The phonostage without the TT going through it is reaaallly loud. When I plugged the TT directly into the amp, it was silent. Does this mean that my phonostage and amp aren't getting along? Is there anything I can do?

Thanks again.