Tri-Planar grounding question...

The two should be the same.

Understood. However, looking at the arm base right now I see the 4 wires exiting the tonearm base and into the arm tube but I can't see where the ground wire is connected to...??

The tonearm cable itself is constructed with the ground wire inside the teflon tubing (along with the 4 signal wires) which is then covered with copper shielding and outer jacket mesh.

If you are concerned about the connection you can test continuity with a multimeter.

The shield does not go through the gimbled bearings. Inside the arm tube, the tube itself is the shield. So the arm ground is usually picked up somewhere near the base, probably very near where the wires transverse the gimbles.

There is a small screw on the base of the arm that goes through a small flat washer which acts to ground the arm and wire shield and also as astrain relief andsecuring screw for the cables leading to the preamp.

Ok. This all makes sense to me now... thanks guys!

WIRES - I see where the screw is and it looks like the washer is in fact attached or soldered to the shielding of the cable.

Is it common practice to attach the ground wire to the tonearm and the shielding together? Wouldn't this create a ground loop? (Just wondering...).

Dogpile, It is my understanding that it is common among shielded interconnects to connect the shield to the negative wire, which can cause a ground loop since the negative wire often does double duty as the ground.

If in the Triplanar, if the shield and the tonearm are connected to the ground wire which is in turn connected to a grounding post that is out of the signal path, then I don't think such an arrangement would contribute to a ground loop and would be superior to affixing the shield to the negative wire in the interconnect.

If the grounding post is connected to the negative wire somewhere in the circuit downstream, then such a configuration could contribute to a ground loop.

I think this is arguably an advantage of xlr interconnects in that the shield is never connected to the negative wire and the ground is altogether out of the circuit.

This is my beginner understanding of grounding topology. Perhaps Ralph or somebody with more grounding understanding will jump in here.
Jeff

Jeff, I think you got it right. The reason it is not a ground loop is that the only place the ground occurs is the shield of the cable. Without that connection to the arm, the arm would be floating and it would buzz like crazy!

This concept is common to nearly all tonearms BTW (including BSRs from the 1960s). Since the arm is a separate ground circuit from the cartridge wiring, it is also why tone arms are or can be a balanced source.

All you cats have been a great help - a very kind thanks : )

I have one more Tri-Planar connection question;

What is the black ground wire (within the cable) attached to on the rca end? Is it attached to the cables shielding or nothing at all?

Dogpile, my setup is balanced, but the wiring is identical up to the box in the cable. The Black wire is the shield up to the box and connects to the tone arm ground itself. After the box, the black wire breaks out to its own connection, and ties to the ground pin of the preamp at its input.

A while ago, I documented the conversion of a Tri-Planar from RCA termination to balanced XLR, for use with my Atma-Sphere MP-1 preamp.

The photos in this website might help you visualize the discussion above: http://www.galibierdesign.com/prd_triplanar_xlr_build.html.

Of particular interest, after this termination is complete, the braided shield you see will have electrical continuity from the tonearm's headshell, straight through to pin-1 on the XLR connectors.

Cheers,
Thom @ Galibier

Atmasphere. I see where the black ground wire exits the box and have opened the box as well to see wire configuration.

The black ground wires which starts from the tonearm pillar DO break up within the box but also continues along the two L/R signal cables as well.

I can't unscrew the rca plugs for a peek since they have been wrapped with heatshrink.

Dogpile, the ground shield on Tri RCAs just ends before the it makes any physical contact with the RCA plug. It goes up as close as possible so the heatshrink has something subtstantial to shrink to so it makes a robust physical end that can be pluged and unpluged with out risking breaking the thin lead wires running up from the cartdrige. The fairly large RCA plug is not 'shielded' itself as the outside is the negative signal input. The RCA only has electrical connection with the plus and negitive connections from the cartdrige.

I used Thoms link to change my RCA to XLRs. (Thanks Thom, and for any body who may not know already, he is a great contributor to this board). Later I changed back to RCAs.

With the RCA setup the ground wire is connected to the shield at the box which is about 80% up from the cartdrige. With an XLR you can run a third wire into the XLR plug from the end of he shield for the ground which makes the already existing 'ground' lead redundant.

I hope that helps.
Terry