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.

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.
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.
Sure, it's possible that some hum could be induced there. However, the hum is coming from somewhere, in order for it to be induced on that cable. The wires themselves are not causing the hum, they are just picking it up. Unless there is a wiring problem or dirty connectors.

One thing about your description, is that you seem to state that the loop is somehow separate from the rest of the internal tonearm wiring. This is very unusual. I have never seen a tonearm wired so that the loop is not a continuous section of wire that includes the tonearm wiring. How do you know that the hum is not coming from the internal tonearm wiring? Is there some kind of plug that the loop plugs into at the tonearm, and you can isolate it from the internal tonearm wiring? If so, that may be part of your problem. There should be no breaks in the tonearm wiring from the cartridge clips, all the way to the final RCA plugs. Any breaks cause signal loss, and if they get dirty or have some oxidation can cause this hum.

Something sounds very unusual about this circumstance. What is it? If you have made modifications, tell us so we can properly determine the problem.

Other than that, I would look at trying to eliminate the source of the hum. As Ron said, it is likely a stray hum field from some of your equipment or power cords. If all else fails, get a different tonearm.
Is step-up transformer switchable in Rowland?
You might have enough gain without it.
Well, if not still you can check hum not using a step-up trans.
Also you can borrow or buy cheap another phonostage to realy check if hum percists.
You may also try to disconnect the ground connector that might create a ground loop in your components starting from your analogue.
Hello Raquel:

This may be a repete of something you have already tried, but here goes.

My analog front end was picking-up a hum that drove me crazy for a couple of days. Like yours, everything "downstream" of the tonearm and cart. was dead quiet.

Mine was cured by moving my digital components away from the analog. That is, my turntable is on the top of the rack, the interconnect runs sideways to another rack where the phonopre and step-up transformer are located, then back to the rack to the preamp. Directly below the TT (on the rack)is my CD transport, with the DAC below that, the preamp below that, and finally, the power filters on the bottom. The amp is located below the phonopre and the step-up transformer on the second rack. It makes some of the IC's visible (running between the racks) but I no longer have a hum.

Good luck, Dave.
I'm using VDH black beauty with Graham 1.5T on a VPI table.
I was using Counterpoint SA-2 step-up with Marantz 7c and now switched to Counterpoint SA-5000.
I had hum issue before but due to bad grounding from the phono cable (loose connection) It could be that your ground for the phono is loose somewhere.
I had a bad hum from a VPI PLC power line conditioner until I relocated it away from the turntable and preamps. The SDS is OK.

It should seem that five or six inches of unshielded cable wouldn't pick up that much AC interference unless there were a really big source of interference nearby. Could there be a high voltage line in the wall behind the turntable? Doesn't sound like it if you've had this problem in two different apartments. What about the turntable motor (God forbid)? Is there still hum when it is unplugged? Presumably you've observed the hum when the motor hasn't been running.

Perhaps one of your plugs is improperly wired, e.g., the plug on the end of the exposed cable that goes into the junction box and/or the junction box itself. Is there some way to plug your arm cable into your interconnect, bypassing the junction box? (This may require some kind of adaptor.) Laborious though it may be, consider connecting your cartridge directly to the phono preamp with another set of leads (maybe cheapos from Radio Shack) that don't go through the tonearm at all. Of course, you couldn't play a record, but you can still see if there is hum while the arm sits on its rest. This test would isolate the cabling between the cartridge and the junction box, as well as your interconnect.

If all this results in a reaffirmation that the exposed wire needs to be shielded, try getting some shielding material (webbing) from Radio Shack to wrap the cable, and think about how to ground it. Perhaps the manufacturer could recommend a way to do this without interfering with the mobility of the tonearm. Good luck.

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.

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.

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.
Do this diagnostic test, if you haven't already, just to confirm your suspicions: Try manually introducing a temporary shield around each of A) The exposed wire, B) The tonearm, and C) The cartridge/headshell, simply by surrounding the part in question within your cupped hands while monitoring through the speakers at a revealing volume (or maybe even better yet through headphones, if possible). If the hum is being induced from outside interference in any of these parts, the level should be noticeably attenuated when you cover it up in this way. On the other hand, if there's no changes at all, I would move on to suspecting something internal...
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.