Exposed tonearm cable source of hum??

Thank you, but from your response, I see that I was not sufficiently clear about the "loop" of tonearm cable to which I refer. It is not the 1/2 inch or so of wires connected to the cartridge that is at issue, but, as is the case with some linear tracking and VPI arms, a five-to-six inch section of exposed wires arching from the arm to a junction box to which is attached an interconnect (this one shielded) that is the direct connection to the phono stage. And again, the problem only arises when the "electrical link" consisting of the five-to-six inch section of exposed wires (and the cartridge) are connected to the system. The interconnect running from the junction box to the phono stage, the phono stage and everything else in the system has no hum, even at full volume, UNTIL the loop part is connected.

Thanks again.

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.

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.

Thanks for the previous post. I tried that already and it yields no change.

The plot thickens, however. This morning, I was fooling around with the cartridge leads again, as well as the interconnect running from the junction box to the phono pre-amp, when I discovered that, while the blue ground is indeed the "trigger" for the hum, the hum only comes out of the left speaker, regardless of whether the blue lead is on the left or right channel, and most bizarrely, regardless of which channels the junction box interconnects are connected to. This would suggest that there is something in the system which "inhabits" the left signal path that does not like the blue ground lead. I have not yet had time to start going back through the system, component by component, to find out which component has a left channel compatibility problem with the blue lead -- it is a royal pain for me to switch phono preamp or preamp interconnects (two hour job) because of the component shelf I had made, so it may be awhile before I continue the fight.

Thanks to all.