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Odd Grounding issue

Reiver

Reiver

Member
Hi Folks,
perhaps someone else out could offer a suggestion as to what might be happening here.

The issue is this: when I ground my deck & / or tonearm (the deck and arm have separate ground wires) to anything, be it the back of the amp, a radiator, a screw into the wall whatever. I get a loud and unpleasant hum as soon as the volume is turned up above silent.

Now when I disconnect the ground wires from anything the problem goes away which is great, no hum, listening pleasure ensues. However I do wonder what's going on and given the static problems I experience wonder if the lack of grounding might be causing / contributing to the static problems.
In the end I wonder If I am worrying over nothing, burt I am somewhat perplexed and would like to understand!

thanks Folks
Reiver
 
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Maybe it's a "ground loop". Musicians knows it very well, unfortunately, because it happens a lot with pedals and gears that are not well grounded.
Did you try to connect both cables to the same spot? Or to different spots?
 
Hi Enderwiggen,
I have tried both, separate spots, the same spot. Also to each other. a ground loop is what I was thinking, but I'd have no idea how to get around the problem (short of leaving the system ungrounded as is).
I am also thinking I need to check that the amp is properly earthed, it's a while since I've had the plug off it...
 
I had this problem once with an old Kenwood integrated amplifier and a Dual turntable. Well, actually it was *any* turntable with that amplifier. The complete opposite of what one would normally expect held true....connect the ground wire--nasty 60 cycle hum. Disconnect--silence. So I left it disconnected. Am I going to Audio Hell?
 
I like to spit in the "Safety Nazis" face anyway, so...

That Kenwood amp found a different home long ago during a rummage sale far away.
 
If the deck did not come with separate ground wire, don't ground it.
Why are you grounding it to a house ground?
A little indication of what gear you'r using could be helpful.
 
I don't believe the tiny gage turntable ground wire is for safety but rather for the sound quality. A ground wire that is for safety is designed with much heavier wire to carry high current in order to trip a breaker should a hot wire inside the appliance touch the frame. In the old days before grounding wired circuits it was common for a ground fault to bite you as the hot touching the frame of say a refrigerator would just make the fridge door or any metal part hot but have no path to ground until someone came and touched the fridge and the sink and then zap! My old Kenwood amp has a place for a turntable ground but was not designed to be grounded itself because in 1975 there were not many household circuits made for a 3 prong plug, thus no ground wire circuits. I'm not exactly certain what the tt ground does as I am an electrician and not a Audio electronics guy but I am guessing it has something to do with feedback. I don't believe it is needed or even desirable for it to have a path to earth ground.
 
Alobar said:
I don't believe the tiny gage turntable ground wire is for safety but rather for the sound quality.
Click to expand...

Correct.

Some cartridges have one of the 4 tags connected to the cartridge body so the tonearm is connected to 0V via the tonearm signal wires. If that's the case, connecting the turntable/tonearm's ground wire to the ground lug on the amplifier creates a second 0V path and an "earth loop" is created. Actually, the name is a bit of a misnomer - there doesn't have to be any connection to planet earth to generate the hum.
 
I wonder if there is some sort of "noise" in the ground path that is causing the hum you are hearing when attached to any ground in the house. It is possible that the problem isn't with the tt but somewhere else in your home. They do make all sorts of power filters and whatnot and that may or may not be needed. I know that commercial buildings go through great lengths to get clean ac power to computer rooms as well as hospitals have special circuits for sensitive equipment. A Turntable is rather sensitive however I doubt not having the ground attached would increase the snap crackle you are hearing with some of your records.
 
If its the Technics deck in your signature, then it could be an issue with the tonearm wiring as that ground wire is not a safety measure as Alobar describes. If you get no hum with that wire disconnected, I would not connect it and move on (which is a generally followed practice). I doubt that is causing any static issues with it disconnected.
 
Nice one guys, Thanks for your input. My system is as my signature, except its an SL150 mk2, which is the version with no arm. I have an SME 3009 on it. Frankly given all the investigating and reading around Ive done on this today I tend (now that you have put my saftey concerns to bed) to agree with tose who say leave it disconnected and move on.

Thanks again
Reiver
 
UPDATE:

Changed out the cart tonight to try and eliminate another possible issue and I note that with the new cart (a Shure M97xE) Not grounding to the amp in the traditional way causes a horrendous level of noise. So I am guessing that somehow the issue is related to the v15 type three I have been and will go back to using.
 
First of all, lets get one thing straight, the "ground" wire on a turntable is not a safety "ground". Because of the huge gain found with turntables, the metal and electrical system(s) act like antenna. They gather all kinds of electrical noises from adjacent components, transformers, motors and things like that. The "ground" wire is actually a "noise drain" wire and carries away all the nasty noise that the turntable metal collects.

There should only be one ground wire connected as 2 points will almost always have a differential to "the drain" ground, and cause hum, or "the proverbial ground loop". If the tonearm has its own ground wire, I would first connect only that wire to the "drain" ground. The hum should go away.

'ner
 
Thanks WaynerN,
I am now clear that its not a safety issue. Misreading s**t on the internet confused my poor little brain on that score. However, given that I have tried every possible combination of ground connection with the offending cart (see my previous post) I am simply gonna leave the deck ungrounded as doing so removes the hum.
Thanks for your input
Reiver
 
Now here's a thing,
Just reconnected the V-15 cart and, ahem, emabarresed cough, It now needs grounding. It appears I may have screwed up the connections when I last set things up. Not sure what I did wrong, most likely didn't get the green ground wire connected properly, however, this post is now moot and I hang my head. I guess its easier to make mistakes than it is to either notice or accept them. You live and learn.
 
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