2. analog
  3. 1054175497

Exposed tonearm cable source of hum??

I run a 0.65 mv. output van den Hul Frog through a tonearm that features a looping, exposed (in the sense of lacking any real shielding) tonearm cable such as are found on some linear tracking arms, VPI arms, etc. (brand of tonearm to remain nameless so as to keep passions to a minimum). The tonearm cable becomes shielded after the "loop" and runs to a Rowland Cadence phono stage that features a built-in step-up transformer, i.e., I have a lot of gain. I have had a consistent hum with this set up in two different apartments. After consulting with the manufacturers and trying nearly every conceivable fix, I narrowed the problem down to the cartridge / exposed-loop portion of the tonearm cable which is the sole source of the hum (everything beyond the "loop" going in the direction of the speakers is dead quiet). Because the cartridge leads are connected properly, my guess is that it is the five or so inches of looping tonearm cable that is introducing what is a quite audible hum.

Does anyone out there know if such exposed tonearm cable "loops" are indeed known to be sources of hum? If yes, is there a fix (I can't imagine what that would be) beyond switching to a different tonearm cable design (which would mean, practically speaking, going to a different arm)? I have been listening to a lot of chamber music recently and the hum is starting to really bother me.

Thanks in advance.
raquel

Showing 1 response by jafox

jafox
1,470 posts
 
Hello,

I think if you would specify which arm you are using, you are more likely to get specific ideas from other owners of the same. As it stands, all anybody here can do is shoot in the dark the hum problems that they have had and what they did to fix it. But most likely your problem is very specific to what you are using. The more details you can give to the group, the more likely your problem will be resolved.

I have a Clearaudio Ref TT with the TQI arm and this too has an unshielded 4" loop of wire over the top and then another 6" or so of wire to the terminals. A shielded tonearm cable then goes to the phono stage. And I have moved line stages (ARC and BAT) and phono stages (BAT and Aesthetix), CD players and DACs (Tube and SS) next to, underneath, etc., this TT and no hum at all. And power cords are going all over the place! So I doubt that it is this small loop of unshielded wire causing you all the pain. It sounds more like a not very solid tonearm lead connection, potential internal short or poor grounding.

I also have a Versa 2 TT which too has a 5-6" loop of unshielded wire above the arm and I have heard of no reports of hum from people out there either. If moving the TT across the room for a simple test does not alleviate this problem, I would suspect that the problem is internal to the arm's wiring and termination .... and not the small length of unshielded wires.

John
More to discover