Grounding problem: I'm clueless

Hi folks,

I'm getting a serious buzz/hum through my speakers when listening to vinyl.

-Kenwood KD500 w/Rega RB300 arm and Grado Gold MM cartridge
-Antique Sound Lab Mini Phono tubed phono stage
-Audio Aero Prima hybrid integrated
-Silverline SR15 monitors

The previous owner of the phono stage attached a ground plug to the outboard power supply, he said it got rid of the hum for him. No such luck here. I've tried running a ground cable from the turntable to the preamp, and from the turntable to the power supply. It's quieter when attached to the power supply, but still not really acceptable.

Some more info: power is being filtered through a Shunyata Guardian. Once in a while I'll heard a very faint radio signal through on of the speakers. Not sure if any of that matters, but there it is.

Any advice would be much appreciated.

On the face of it, it sounds like you have a ground loop somewhere. Was the hum introduced into your system when you introduced the turntable? Also, by a ground plug, do you mean a "cheater" plug (converts 3 prongs to 2 prongs)? If not, then a cheater plug for either the phono stage and/or turntable could be the $1 solution.

You can also try plugging either the phono stage and/or turntable directly into the wall socket (bypass your Shunyata Guardian) and see if that takes away the hum.

If you have your cable TV hooked up into your system, that could be the culprit as well. The $100 solution then, would be a product from Tributaries called a "Ground Loop Eliminator." It is available from Audio Advisor .

Regards, Rich
Grado Prestige Gold is unshielded cartridge. Unfortunately with DD turntable always to hear hum.
Sorry for my poor english.
Hi Rar1,

Thanks for your response. There has always been a tiny bit of buzz from the amp, but it only got to be a problem when I added the turntable.

I don't think I'm using the term "ground plug" correctly. The previous owner attached a metal nub on the power supply right next to the power cord. I've been running the ground cable from that nub to the turntable.

The turntable's power cord is permanently attached and it is two-pronged. I tried plugging it into the wall, no difference.
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?
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.
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.
Hi - Sorry for the delay. There are so many possibilities that it's pretty hard to say what's going on without being there.

Assuming all the plugs are polarized (either 2 prong with one big/one small or 3 prong), the first thing I'd try is a "star grounding" pattern of sorts by grounding every single piece in the system to a single point that you know is good - on the amplifier if it has a specified ground screw, or on the Shunyata if it has a provision for that.

Another thing I'd try, if the condition of the tubes is unknown, is substituting them. I don't know the ASL's but I assume it's a pair of 12ax7's or similar which aren't hard to come by. If you don't have spares maybe someone nearby could lend you a pair to try out.

Also since it really appears that it's the Preamp/Power Supply and not the TT, I'd call ASL and talk to them.

Another remote possibility comes up because your amp is of European origin. The grounding scheme/wire colors are different over there, and sometimes people doing mods or setting up equipment to run here get the polarity reversed.
If you want to double check everything, here's a chart of what the internal wiring should look like if it was done to accepted standards:


Europe____Green/White or Green/Yellow__________Brown_____Blue


USA Plug type____Round prong_______________Small prong___Large prong