I must not be as skilled:) |
Like Peterayer, I didn't install the finger lift on my SME V when I had one years ago, for the same aesthetic and sonic reasons.
I never use finger lifts anyway: that what the tone arm's cueing lever is for! |
Rsnoceanview - good luck, I know how frustrating this can be. |
I like the heat shrink option (if I can't eliminate the hum source) for better aesthetics and will also check out the rubber shoes/mat just to see what happens (more evidence). |
Lewm, not quite correct. Additional observations were
I was explaining to the gentleman why touching the SME armtube did not induce hum - anodising.
Provided additional options for insulation on the arm for aesthetics - get a painted one or use heatshrink rather than plastic.
Rubber shoes/mat I cant see anywhere - a bit off the wall, but I have seen this work.
I refrained from suggestions like removing his pacemaker or turning the cellphone off.
I have also seen hum issues or rf issues where there have been poor solder joints in the cable loom between the cartridge phono input sockets that whilst hum is not present, touching the arm induces it - not a ground loop issue, more of an antenna effect. |
Dear Dover, If you re-read the thread you will see that every single point you made has already been made, and your "theory" has already been proposed. At least you and I and others agree. Insulating the finger-lift has apparently worked to eliminate the hum; the OP is not totally happy, however. |
I have an SME V arm and have never installed the finger lift. I don't want another piece of metal that could vibrate a tiny amount between the headshell and bolts near this sensitive part of the arm and cartridge. I don't know if this sounds better or even different as I have never compared, and perhaps it is just a silly precaution, but rather than take the chance, I just left it off. My dealer also suggested this when I bought the table years ago. It looks more elegant anyway, IMO and I don't miss the convenience of the finger lift. This should solve your problem. |
If the SME V arm tube is anodised, then this explains why it doesn't hum when touched- anodising gives a non conducting surface.
The question here is what finger lift are you using. It would seem to me when you are touching the arm lift or cartridge bolts you are creating a ground loop.
If my theory is correct then finding an arm lift with a non conductive coating is the answer - and gets rid of the plastic problem. Another solution you might find more elegant would be to put some heat shrink on the arm lift - just the part you touch. You can get different colours including clear.
You could also try wearing rubber soled shoes or put a rubber mat in front of the tt to stand on to break the earth loop. |
It's certainly a workable solution since it's what I am doing and when actually playing a record it sounds fantastic, but I will still be experimenting until I find a 'permanent' solution. The concern about the tight and rigid coupling with the Lyra to the headshell being compromised is a concern of mine as well if nylon screws are used. Thanks for all the advice. We'll see where this goes. |
If I understand the situation, this was NOT an issue with a prior cartridge, but, it is an issue with the Lyra Argo. If that is the case, it may be the case that the Lyra's aluminum body is part of the conductive pathway. In that case, you may be able to do something with plastic screws, but, depending on how conductive is the headshell and the body of of the Lyra, you may also have to put some kind of barrier between the cartridge and the body. Keep in mind that the Lyra body is designed to make a very tight physical contact with the headshell in order to effectively drain vibrational energy from the cartridge into the arm for dissipation by the arm. That "insulation" might compromise that objective.
In short, I would go with Lewm and consider insulation of the armlift as a permanent solution. |
Unless I have completely misunderstood what is going on here (and that is entirely possible), I don't quite understand why you are so exercised over it. If insulating the lift has cured the problem, I especially do not get it. I would think of that as a "permanent solution" and go on from there to enjoy the music.
For example, my dedicated MM phono stage will put a low level buzz on my speakers, if I don't dress the umbilical cord from its power supply so as to be clear of the AC cord. So I taped it up to stay away from the AC cord. I consider that "case closed", but the reality is not unlike the one you describe; I used a bandaid to fix a problem. So what? |
All grounding effects have been tried (on the SME there are three into two grounding cables from the arm). None, either one, both. No change. Checking additional items, there is no hum (and it is a hum, not a high pitched sound) at the arm tube, headshell or cartridge body. But there is at the finger lift, tops of the headshell bolts and the front bolt on the Lyra. For now, have insulated the finger arm with plastic, but would like a permanent solution. That could be a new cartridge or replacement of the stainless steel bolts/screws with non-conductive bolts/screws (nylon or carbon fiber?). Has anyone tried that and if so where to procure? Thank you. |
Hi Larry, That's what I originally suggested - insulate the arm lift OR don't touch it. If the system is elevated from true ground for some reason, for example due to a faulty wall socket, it is conceivable to me that one's body could be at a lower potential. When you contact the arm, only then is there a loop. There are several variations on this theme, but I hope you get my idea. The body as antenna usually results in a higher pitched noise, not true hum.
Also, if the tonearm is grounded to the phono stage, as someone else suggested, it might be of interest to un-ground it. If we then don't have hum, my hypothesis is supported. Anyway, changing the current grounding scheme, whatever it is, might reduce or enhance the problem, and that information would be valuable. |
Unless the person touching the arm was also simultaneously touching another another component which has a different potential, I don't see how this is a ground loop. It seems like the person's body is acting like an antenna.
The easiest solution would be to cover the armlift if this really is a problem (perhaps shrink wrap with heat applied directly to the wrap and not to the cartridge itself). |
IMO, if there were an overall issue with grounding the tonearm (i.e., if there were a potential difference between his tonearm and his phono stage, for example), the hum would be audible at all times, whether or not the OP touched the finger-lift. |
Dear Rsnoceanview: IMHO is a problem with an ungrounded tonearm or/and TT. Even that you already try every ground combination could be that the ground wire in the tonearm is ( for whatever reason ) not soldered.
I think you have to check for continuity with a multimeter as other ground connections.
Regards and enjoy the music,
R. |
try pulling tt ground wire off its post.see what happens. |
Your body is creating some sort of ground loop. If this is really an issue, you could cover the finger lift with some heat shrink tubing, or any other form of insulation. But be aware that this will increase tonearm effective mass. Otherwise, the obvious retort is "don't touch the finger lift while LPs are in play". Why would you ever want to do that? |
As you mentioned, it is a grounding issue. Is it an SME arm? Could you list your phono-pre and preamp? |
