Years ago, I made 2 primitive Well Tempered style tonearms, one, using an older WT tonearm, the other I made with a carbon fiber tube. Both had a hum, the WT arm's ground wire, it seems, was broken and no longer reaching the screw behind the cartridge mount. Once I got a 3d printer, I began experimenting with carbon fiber arm tubes. I made 2 self standing arms, one 9" and the other 10.75". The arm tubes were quite narrow and I didn't know enough to add an internal ground wire, so, again, both had hums.I've tried again, first using a 10mm diameter carbon tube and a woven, flexible metal tubes for each pair of signal wires, which I twisted with 4-5 turns per inch. I soldered a wire to the 2 internal woven metal jackets and ran it out with the 4 signal wires to an external PIB box. I 3d printed numerous parts of these Well tempered clones (golf ball style), including the cartridge mount. I still got a hum. Perhaps the ground wire came lose.
I tried again, using a brass tube inside the carbon fiber arm tube. I fastened the ground wire to the arm tube, separated the signal wire pairs, twisting the pairs separately and feeding them thru different holes in the arm tube. I ran the ground out the hole with the right signal pair and connected the twisted pairs and ground to the integrated PIB box on a Well Tempered Simplex table, modified with older Well Tempered parts - bearing, spindle and platter (I bought it without arm or its support parts, spindle, platter). I added an extended base on this table to accommodate the taller WT bearing. I used another plastic printed cartridge mount. STILL a hum. As a test, I ran a wire from the exposed end of the internal brass tube to the ground post, hoping this would stop the hum, but the hum continued.
I am now preparing to replace my arm on the Simplex with the original Well Tempered stainless steel armI IF the broken outer ground wire can be fixed. A friend told me NOT to connect the ground the a headshell made of metal. What have I been doing wrong?
Here's a pic of my Neat-made Shield MO-19 idler with the 12" arm.
I tried again, using a brass tube inside the carbon fiber arm tube. I fastened the ground wire to the arm tube, separated the signal wire pairs, twisting the pairs separately and feeding them thru different holes in the arm tube. I ran the ground out the hole with the right signal pair and connected the twisted pairs and ground to the integrated PIB box on a Well Tempered Simplex table, modified with older Well Tempered parts - bearing, spindle and platter (I bought it without arm or its support parts, spindle, platter). I added an extended base on this table to accommodate the taller WT bearing. I used another plastic printed cartridge mount. STILL a hum. As a test, I ran a wire from the exposed end of the internal brass tube to the ground post, hoping this would stop the hum, but the hum continued.
I am now preparing to replace my arm on the Simplex with the original Well Tempered stainless steel armI IF the broken outer ground wire can be fixed. A friend told me NOT to connect the ground the a headshell made of metal. What have I been doing wrong?
Here's a pic of my Neat-made Shield MO-19 idler with the 12" arm.
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Are you using an MC cartridge?
MM cartridges usually (always) have one terminal connected to the metal case. The cartridge wires being connected to the phono RCA inputs.
I grounded the carbon fibre tube simply by using a screw connection to the tube.
This leads ultimately to the ground terminal nut on the phono pre-amp, same as you ground any phono stray bits of metal.
Clear?
MM cartridges usually (always) have one terminal connected to the metal case. The cartridge wires being connected to the phono RCA inputs.
I grounded the carbon fibre tube simply by using a screw connection to the tube.
This leads ultimately to the ground terminal nut on the phono pre-amp, same as you ground any phono stray bits of metal.
Clear?
I've used both MM and MC cartridges on this table while testing the arm. Both hummed. How did you shield/ground the signal wires in the carbon fiber tube? Given that a carbon fiber tube isn't metal, not clear how a screw on that and a ground wire connected there, with the other end connected to the phono ground terminal on the phono stage would properly ground the arm. I have some spools of Litz coming that will allow me to experiment more freely. I can drill into the bottom of the carbon tube and insert a screw thru that and into the internal brass tube, then connect a ground wire there, with the other end at the PIB box's ground terminal.
Here's the Simplex table with another self-made arm.
Here's the Simplex table with another self-made arm.
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The diagram from the link below shows where to open the ground points (each point marked with X) to provide an osolated ground path for the audio signal, effectively converting the cart to balanced. The arm then also has a single path. It might be worthwhile.
https://lathetrolls.com/viewtopic.php?t=5876
https://lathetrolls.com/viewtopic.php?t=5876
I have no tonearms that have a DIN or multi-pin connections. My arms terminated to an external PIB box with unbalanced jacks and a ground terminal. Blew my mind testing continuity with the multi meter. I'll try adding a hole and screw on either carbon arm tube and connect to a phono stage ground terminal. I have Litz wire coming at some point soon with which to play.
I've always wondered how Well Tempered has been grounding their carbon fiber arms. The Lary Pederson LP Labs carbon fiber arm is unusual in that the arm wires are freely moving in the carbon tube. He has a screw on the bottom behind the headshell where the ground wire is held in place. It then goes into a hole and out the hole with 2 of the signal wires, terminating at the phono stage ground post.
I've always wondered how Well Tempered has been grounding their carbon fiber arms. The Lary Pederson LP Labs carbon fiber arm is unusual in that the arm wires are freely moving in the carbon tube. He has a screw on the bottom behind the headshell where the ground wire is held in place. It then goes into a hole and out the hole with 2 of the signal wires, terminating at the phono stage ground post.
When I measured a carbon fibre tube, it didn't conduct. Yes, carbon is a conductor, but the fibres are buried within an insulating binder. Thus, you have an arm tube that doesn't screen the wires within, so I would expect it to hum, irrespective of how you take an earth to the cartridge. One solution would cover the outside of the tube with self-adhesive copper tape. But I've always suspected that people use carbon fibre because it looks nice. Lining the tube would be much harder. There are spray-on conductive films intended for static dissipation and EMC, but whether they would work in this application is another matter. Another possibility is to screen the wires before inserting them down the tube. That could be some braid or an additional (very thin wall) tube. I suspect an earthed thin wall 4mm diameter tube glued to the inside of the carbon fibre tube would work best. So your earthed brass tube should have worked. Glued with epoxy all the way along, it might even damp the carbon fibre tube's fundamental bending resonance.
I used a woven mesh for each of the pairs of leads, soldered the ground to each mesh and taped the wire to the mesh to prevent it being dislodged. I then ran the ground out of one of the 2 holes made near the pivot for each pair of of leads and connected the ground wire to the PIB ground post. As I was further setting up the arm, I caught a wire with a finger... (BIG fingers and tiny wires!). I may have pulled or broken the ground wire on that arm. On the other arm, I used a brass tube inside the carbon outer tube, connecting the ground with to the brass. Perhaps the brass rod isn't the best for shielding? I to need to twist some of the wires leading to the PIB box a bit more. When I get my spools of Litz, I'll have more material with which to play. it seems the best solution is to copy what LP arm does = drill thru the bottom of the carbon tube and insert a small screw, washer (and nut inside the tube ) to secure the metal mesh to the carbon tube and run the ground out of a hole, terminating at that little screw/bolt.
I'm not an expert, but if that tonearm were mine I would try to use something like this first, for its lightness (it seems that the available thicknesses can vary from 5µm to 150µm), easy removability and versatility.
https://www.finfoil.com/en/products/materials/aluminium/
https://www.finfoil.com/en/products/materials/aluminium/
All 4 signal wires need to be twisted or woven together, not in pairs. Pairing them up causes a loop in the ground common to both signals. I have a Schiit Sol with CF wand and metal shell. Internal loom is 5 wires (5th wire grounds the shell) twisted together and terminated with a 5pin molex connector for quick arm changes. Signal and shell/chassis grounds are separate. No hum.
This may easily become an issue in the vicinity of the bearing. 5 twisted together wires don't have the same compliance as 5 loose ones.