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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 rockinroni

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rockinroni
287 posts
 


Raquel,
You need to check where your phono and your phono section cables are. As well as your tonearm cables.
If they are near any power cords you will pickup the ac line hum. It could be your phono section is to close to your power amp and picking up the field off of its transformer.
You have to play around and see how by moving stuff around this affects the hum.

I had a hum problem, I noticed when I moved my tonearm to is rest I had more hum, Yes it was getting closer to the transformer in my power amp so I switched places, I moved my pre amp next to my table and my power amp further away.
I still had some hum and some RF. I have a outboard phono, it was to close to a powercord I moved It away from the cord and then silence.

It wasn't quite that simple, I had to play around with the position of the phono section. I have a out board motor controller, I cannot have this any where near my preamps or hum again.

You will always have the leeds of your tone arm cables coming off your cartridge the way you do, this should not in and of itself cause hum.

I hope you can use some of these Ideas and get rid of your problem.
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