2. tech-talk
  3. 1205025054

Arm cable - soldering shield & ground? Please help

Hello Chaps,

This is my first post in this forum even though I bought and sold a few things in Audiogon. I live in the Washington, DC metro area, have been tinkering with audio for almost thirty five years but I am unsure as to what to do in this case.

I would like to replace the original tonearm cable in my Thorens TD147 Jubilee with a Van den Hul M.C. 501 silver hybrid cable that I found in my parts bin. One end has SME RCA plugs, the other is unterminated.

When I built my own cables from scratch I always cut off the shield at both ends but the Van den Hul cable comes factory assembled with the shields connected to the grounds in the RCA plugs.

My question is, do I cut the shield off at the tonearm's end [unterminated] or do I solder the shield with the ground as it has been done with the plugs?

I’m trying to avoid possible hum problems.

Please advise.

Kind regards,

Orazio
f456gt
mingles
796 posts
 
My question is, do I cut the shield off at the tonearm's end [unterminated] or do I solder the shield with the ground as it has been done with the plugs?

I’m trying to avoid possible hum problems.

You may want to try it both ways.

When I rewired an RB-300 with a single strand of Cardas 4x33, I grounded the shield that wraps the Cardas wire to the tonearm and then let it float on the RCA end (there isn't anywhere to ground it to anyway since this is DIY cable). I have a second sheath of braided stainless steel over the length of the Cardas cable and it's completely floating. It's probably overkill, but there isn't a trace of hum in my system. I also run a ground wire from the table to the phono preamp. Without that, I get hum.
f456gt OP
38 posts
 
Sometimes I wonder if it is an overkill like you said.

I have had two Breuer tonearms in the past, both had five monofilament wires, unterminated, as thin as sewing thread without any kind of shield or cover, just five loose wires hanging, unbelievable. That is Breuer's idea of tonearm wiring and I can assure you that I never had a trace of hum. One was mounted on a Lin LP12, the other on a Michell Gyro limited edition.

Bear in mind that all Thorens manuals always make reference to possible hum problems.

Regards,
nsgarch's avatar
nsgarch
2,524 posts
 
Hum is generally produced by either the TT itself (thru the motor/chassis) or is picked out of the air by the cables. Which one is the culprit is very much a function of the cartridge type. MM with their enormous coils tend to pick up TT motor hum, while MC with their tiny coils don't/can't pick up much TT motor hum, but because of their tiny output, hum picked up by the tonearm cables becomes a big factor.
f456gt OP
38 posts
 
I did replace the arm cable without connecting the shield to the strip terminal - left it floating as Nsgarch suggested.

There is absolutely no hum at all.

Many thanks,
More to discover