Exposed tonearm cable source of hum??

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

Thanks to all for your input.

The previous post is certainly correct that it would be much better to provide the name of the arm manufacturer, but this forum is such a hotbed for rumors which can be commercially damaging that I prefer to posit the question generically (even if it means I am prevented from getting information which might solve the problem). Sorry for making you all stab in the dark.

I have a custom MDF stand that has the turntable and turntable motor on top sitting on two inches of MDF, the pre-amp below it on next shelf, transport below pre-amp on next shelf, processor below transport on next shelf, phono pre-amp below processor, and PS Audio 300 on bottom. I have monoblock amps that are 20 ft. from the source components and in another room. There are no interconnects or power cords dangling freely and visibly behind or under the components -- all are ported through small holes behind the components and thus hidden behind the component shelf (and thus somewhat sequestered from the components). I had the turntable on a totally different shelf in another state with completely different components (no PS Audio, for example) and had exactly the same problem. I also ran the identical turntable / arm / cartridge into the phono stage of a CAT pre-amp for two years with no hum, but the CAT, which has no step-up transformer, has roughly twenty decibels less gain than the Rowland Cadence I am now using. I've tried floating the ground, star-grounding, filters, moving components around, reconnecting the leads to the cartridge, plugging compenents onto different A/C lines, using different interconnects from the junction box to the phono preamp, but nothing helped. If the loop is disconnected from the junction box, I get zero hum, regardless of volume setting. The problem arises only when I connect the "loop" to the junction box, which leads me to focus on the exposed loop becoming a problem if used with a high-gain phono stage.

Thanks again.

One more thing ... the problem exists whether the turntable motor is on or off, and regardless of the position of the tonearm -- these variables do not change the nature or quantity of the hum.

Thanks.

How do you know the hum isn't from upstream of the exposed cable, like from the cartridge or in the arm?

The previous post makes a good point. I had reconnected the leads to the cartridge with the thought that these connections may be the problem, but it changd nothing. What I did not do until yesterday, however, was try switching the leads around a bit. It would seem that the Blue Negative tonearm cable lead is the source of the problem inasmuch as the system has no hum until that lead is connected to the cartridge, regardless of which post on the cartridge it is connected to (I switched the white positive / blue negative to the other channel and also wired the cartridge out of phase with the negatives connected to the positives). As soon as the blue lead hits a post on the cartridge, I get hum. I also connected the cartridge leads to a different cartridge, and the hum is still there (albeit of a slightly different noise signature). I would be prepared, now, to conclude that I have a bad blue lead, but have to, at this point, get back to the manufacturers with this new information.

Thanks to all of you for your help.