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Preamp-Tonearm Grounding Problems?

Can someone HELP?
I am having two problems with my phono section and wonder if someone might be able to help.

The Problems are as follows.

1. No matter what type of tonearm cables I use the tonearm itself is "hot" (touching any bare metal to it pops like crazy) and gives off static discharges that cause pops and cracks either during idle or LP playback. Grasping the underside of the arm on a metal surface stops most of the discharges but not all. In fact I can feel a slight current sometimes when I do this.

2. In tracking down a ground loop as the cause for #1, I found that if I disconnect the tuner either from the preamp or the in-wall antenna connection, dependiing upon which tonearm cables I use I get a "flutter" noise through the phono section either by holding/grounding the tonearm or not.

As far as #1 is concerned, I realize I am acting as a new "ground" by touching bare metal to the tonearm or by grasping the underide of the arm, which stops most of the discharges. I was assuming a ground loop effect from within the system but the only thing I can determine is that unplugging all other cables from the preamp and removing all other AC power cords from the wall does not help.
As far as #2 is concerned, I am not sure if this is related to #1 but I disconnected the outside ground wire of the antenna from its ground post, which is not at the mains ground post, and there is no change in either #1 or #2.
It has been a major source of frustration since tracking it down has taken a long time and considerable inconvience. I have been trying to determine the cause since, 11/99, when I upgraded my TT/arm/cart all at once. Since I did not have the exact problem with my old set up
I automatically assumed it was in the cart. or arm.
I remember checking the new arm in the past for the same issues showing now and do not remember it being the problem. The fact that the dealer I am using is in, San Jose, CA., and I am in, Seattle, WA. does not help, as well as my scant electronics background.

What would cause the arm to be "hot" like it is? It seems like it is a preamp grounding issue now. I have the ability to use phono cards within the preamp, or separate phono cards in a separate case outside the preamp which is powered by the preamp's own separate power supply and utilizes a dedicated inputs in the preamp, or a third party phono stage which utilizes a line stage input and all the same problems take place.

I swapped out my preamp with another one of the same and had the same problem. My amp/preamp are NAIM gear and use "star" grounding, which I do not totally understand, could this be part of the problem? Someone mentioned measuring ground potentials before, do you think this may be the problem? My Ac panel uses a grounding rod as its "ground". I went around and un-hooked all other ground wires on the cold water pipes but no change. I have three separate outlets to use, two are separate 20 amp dedicated lines and the other is the original house circuit. I had the two dedicated lines installed to minimise EMI problems in the phono stage, but it only helped a bit. Plugging the amp/preamp into either the original outlet or one of the dedicated outlets, while unplugging all other items does not alter #1 or #2.
What now? I would really appreciate any advice! This has really ot me frustrated since I can hardly enjoy LP's since 11/99.
Thanks.
Gerard
GerardFF@aol.com
gerardff
gerardff OP
78 posts
 
My equipment list is as follows;
Michell Orbe/Graham 2/Ruby 2 attached to a Naim 52 (K) and a Naim 250 amp. Digital sources are a Arcam transport and DAC as well as a Magnum tuner attached to a roof antenna. Phono Cables consist of either Harmonic Technology or Graham and non phono are Naim or some Kimber.
What I can say at this point is that when the arm is on the Orbe and I touch (with a wire) either the springs, the arm board, spindle, I get the pops. So at this point I am assuming that there is continuity between the arm and the Orbe. If I remove the Graham from the Orbe it still has the problems. The arm cable has no ground wire at the DIN to attach to the Orbe's sub chassis ground screw like a Linn arm cable. If I run a wire from the Orbe's grounding screw to the preamp ground post nothing changes.
Not having another arm to try, Saturday, I borrowed a Linn Basik arm from a local Dlr. and hooked it up to the preamp, and have the same problem! I have it mounted on a wood block cause I cannot mount it on the Orbe. The same problem, touching metal to metal causes pops. I think it rules the Graham out as the source. I hooked the Linns extra ground wire located at the DIN plug to the 52's ground post and nothing changed. I even ran a wire from a cold water pipe in my crawl space and attached it to the above mentioned Linn ground wire and it did not help. I have run an extra wire to the preamp ground to the base of the Graham and it does not help. Only grounding it to myself helps!
The fact that a second Naim preamp of the same model I brought in a while back and tried did similair things says its not my individual preamp.
I have tried cheater plugs on all items mentioned, using in different conmbinations, removed all sources but the preamp and amp and nothing helps.
I know that Naim uses a star grounding approach, is there something going on between the Naim gear and my house AC that may be causing this? The only thing left will be to bring home some non-Naim gear to see if the same problem takes place.
Thanks for your suggestions I look forward to more.
I'm dying here! This is a bugger!

Gerard
tsouthworth
59 posts
 
Sorry for jumping in late so late, but I've lived thru some strange grounding problems, too, and have some different ideas to try.

Since you have dedicated lines, we can assume that there is ground at the outlet. Having never seen Naim gear, have you checked that the 3 prong plug wiring is all attached within the case, or could the ground be "floating" in the Naim?

You have had a ground lead connected to the Orbe with no effect. Have you tried grounding the Orbe and the Graham at the same time, first to each other and then both to the preamp? (Even though there isn't a screw on the arm post, temporarily you could use a cable tie, rubber band or "twistie" just to keep it on there, making contact.

A preamp of mine had a low level hum problem due, somehow, to the brass feet digging in to the metal rack. I had to ground my rack to the preamp! Hum gone! I never would have believed it.

Have you unplugged your AC to the turntable to test any difference in hum? The fact that you can feel a small bit of current in the arm makes me wonder if the turntable/motor wiring is completely insulated from the rest of the base (metal, I'm guessing). Or if you have the outboard power supply, if there might be some sort of leakage that the gain in the phono stage is picking up on.

Good Luck!

Todd
gerardff OP
78 posts
 
Todd,
Thanks for the input. I have checked the two dedicated outlets for proper grounding and they are fine. The Naim gear comes three pronged and I am pretty sure its not floated, plus when I float it there is a difference in noise through the phono stage. I have grounded the Graham to the Orbe and the Orbe to the Naim, as well as; the AC ground at outlet, the cold water pipe under house and the AC bar ground post outside. No good. As far as the Orbe motor, it seems inert in this whole thing as I cannot get it to "pop" with the metal-metal touch test and I have unplugged the power supply to it as well with no differences noted. The Orbe motor wiring is far away from the subchassis and since the motor itself is in a stand alone base, though near to the sub-chassis, it is not seeming to be the culprit.
Thanks for the suggestions. I'll take any I can get!
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