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Ground hummmm when touching tonearm or record clamp

monty

monty

pfm Member
Hello

Had a quick look on the internet and can't find a specific thread on this one....

I've just moved my system to another room and am now experiencing a hum when I touch the turntables arm or any other metallic part of my Gyrodec Rega RB300.

When I let go, the hum stops. If I touch the arm and amp at the same time, the hum reduces.

I've tried hooking up the RB300 cable to my Trichord Diablo phono stage and directly to my Yamaha amp which has an internal stage and the same issue persists, so the issue points to the TT.

Everything is connected to the same power outlet via a mains block. I did have a dedicated mains ring in the old room, but not in the new.

I've checked the 4 cables on the back of the cart (Transfigoration Phoenix S).

Any ideas why this is happening and what I can do to sort ??

Thanks
 
ahhhh. I had hum with the RB300 arm on Roksan Xerxes depending on whether using a MM or MC and whether the cartridge ground connected to the arm ground.( I had moved from a MC Ortofon to a MM 2M bronze. I had originally had it rewired with Vandenhul and I had to take it back due to hum and I had a common ground connected or broken - a long time ago now so cant remember which, I suspect broken - see later ) I also had a further issue with crackling when I touched the arm. I have just looked at my set up into the Musical Fidelity XLPs v3 and the cartridge ground cable I took from the phone plugs I made is not connected to the arm ground cable at the XLPs. Also had an issue with whether I was using my musical fidelity XLPs v3 phono amp or Tag Mclaren PA 10 preamp think it is - in the latter case had to make a real earth to a power socket as the PA10 has a floating ground. For the PA10 I just made a cable with spade connector for the preamp and a plug on the other end with only the earth pin in, that attached to the PA10 case intended for the earth from the turntable.

maybe first try making a proper ground for your preamp or amp?

Good luck its all very annoying.

Hope this gives you some ideas to try
 
Thanks , yes. Just seems strange why it only hums when I touch a metal part of the Gyrodec that’s connected to the tomearm. EG, if I touch the motor, it doesn’t hum.

Once I let go the hum stops, suggesting the earth connected down the cables is OK, otherwise it would hum all the time.

I’m wondering if there’s interference on the mains. I’ll have to try unplugging stuff. I’ve unplugged lamps, the HR power supply and DAC without any success.
 
This is a grounding issue. The TT/arm is not correctly earthed. Perhaps something has come loose/adrift?

Cheers,

DV
 
monty said:
Thanks , yes. Just seems strange why it only hums when I touch a metal part of the Gyrodec that’s connected to the tomearm. EG, if I touch the motor, it doesn’t hum.

Once I let go the hum stops, suggesting the earth connected down the cables is OK, otherwise it would hum all the time.

I’m wondering if there’s interference on the mains. I’ll have to try unplugging stuff. I’ve unplugged lamps, the HR power supply and DAC without any success.
Click to expand...

I think trying to understand it will be perplexing. I dont understand the effects I had why MM and MC needed different grounding policies re the arm ground and cartridge ground. I found this out trial and error. Any way the above is my input into this matter. The easiest thing for you to try is to make a real earth to a plug and connect that to your amps case earth.
 
Grounding, pure and simple.

Most arms have naff little earth cables to be attached at the most inconvenient point possible. I used to just put a bit of earth cable off the back of wherever the earth is before installing it and connect that to the tonearm earth cable.
 
OK - I'll have a mess about. Just weird its only started since I moved to another room
 
Do you have the earthing strap connected between armboard & chassis?

If it's an older Gyro with metal spacers it may not need this, but Michell always supplied an earthing strap with the arm board decoupling kit. You'll need to ensure electrical continuity by scraping a little paint off the chassis underside so the nut makes contact with bare metal.

Try swapping the grounding strap that comes with the Gyrodec onto a different screw beneath the arm board.

Cheers,

DV
 
Darth Vader said:
Do you have the earthing strap connected between armboard & chassis?

If it's an older Gyro with metal spacers it may not need this, but Michell always supplied an earthing strap with the arm board decoupling kit. You'll need to ensure electrical continuity by scraping a little paint off the chassis underside so the nut makes contact with bare metal.

Try swapping the grounding strap that comes with the Gyrodec onto a different screw beneath the arm board.

Cheers,

DV
Click to expand...

Thanks - I'll have a look later. My Gyro is probably 23 years old and I don't remember seeing a strap but will check
 
Hi - ok - mine is pre decoupling kit so there is no earth strap.

Any other ideas?

Thanks
 
You should run a ground wire from the Rega nut to turntable interface to the ground lug of your phono. It is likely that your ground wire, which in the Rega gets a connection inside the counterweight stub, has come loose. If you are lucky, you will be able to unscrew the stub, but be careful not to put very large torque on it, as the only practical way to grab the arm is around rhe bearing yoke. Put a piece of old belt around the stub and grab it with vice grips, but gently. If it doesnt want to come loose, leave it alone and ground at the main nut.
 
Thanks, I upgraded the weight to Techno weight a few years ago so hopefully will unscrew OK. Will have a play this weekend :)
 
Before you take any pliers to your arm I suggest you check for continuity between the cartridge tags and the RCA connectors. The RB300 is grounded via the return wiring - a typically quirky Rega solution. I would also check that the cartridge tags are actually gripping the pins rather than just fitting round them. As others have said, this is not a mains related issue, it is a grounding issue related to the arm.
 
I have a similar issue, having recently mounted an Audiomods arm to my LP12/Kore/Lingo, in that if I touch the arm, I get odd noises. I believe that arm has ceramic bearings, but there is an earth wire attached to the arm tube, which is connected to the ground, so there shouldn't be a problem, but when I measured between the arm tube and the ground connection, there was some resistance there, so obviously there isn't a clean earth for whatever reason.
 
The statement that it has only become a problem since moving to another room may be significant .

It might be worth checking the wiring polarity and effectiveness of earthing at your wall sockets.

If you can get an electrician to check the earth loop impedance at the various sockets that might show something untoward - as well as a possible safety hazard.

Or as others have said, the physical move may have dislodged a wiring connection somewhere between cartridge and amp/phono stage, or the earthing of the combination.
 
Checked the wiring in the sockets and power block, ensured the connectors to the cart are tight, and ensured the RCA's are tight. All OK.

TBH - the hum when touching the arm is only noticeable when the volume is set higher than I'd normally listen at and it stops once I let go. There's no hum when the cart is on the record so maybe I need to move on and accept this is a non issue?

I have noticed the amp and Diablo phono stage is slightly warmer when turned on and idle than previously but I guess this could be due to the warmer weather .... ?
 
I had various hum issues on my Rega-SRM-AO turntable and solved them all (including exactly the trait you describe) by earthing to the phono stage (but not from the phono stage to pre-amp); running an earthing cable from the external TT PSU to my mains conditioner (that made a big difference) and fitting better quality cartridge connectors and wires. The latter were causing all sorts of subtle issues. This was running a 2M Black on a RB303 arm. When I fitted a Musicmaker cartridge I had a dreadful hum that was picked up from the motor whenever I swung the arm over, so the cart had to go back. Grade and Musicmakers can fight with Rega motors, it transpires. That's about all the variables in my experience.
 
kneesup said:
I had various hum issues on my Rega-SRM-AO turntable and solved them all (including exactly the trait you describe) by earthing to the phono stage (but not from the phono stage to pre-amp); running an earthing cable from the external TT PSU to my mains conditioner (that made a big difference) and fitting better quality cartridge connectors and wires. The latter were causing all sorts of subtle issues. This was running a 2M Black on a RB303 arm. When I fitted a Musicmaker cartridge I had a dreadful hum that was picked up from the motor whenever I swung the arm over, so the cart had to go back. Grade and Musicmakers can fight with Rega motors, it transpires. That's about all the variables in my experience.
Click to expand...

was the music maker cartridge a MC by any chance?
 
The Music-maker is a rebranded Grado isn’t it - a moving Iron design? These are notoriously susceptible to hum.
 
Hi all,

Back to this one. I think I’m creating a ground loop when touching the arm. I have a oak floor which is on concrete. Ground floor level, so likely acting as a ground point. I also have a rug on top of the wooden floor, but I stand on the wood around it when touching the arm. If I stand on the rug, the hum is less obvious, but still there.

Like I said previously, when I let the arm sit on a record and play music, there is no hum. I only hear it when touching the arm, or any other part of the gyro (except the motor housing).

To conclude - is this a non-issue and i’m Just adding a 2nd earth point creating a hum ??

Hope this makes sense !

PS - the room I move the Hi-FI from had a suspended, carpeted floor

Ade
 
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