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Topic: Turntable Ground Wire (Read 16042 times) previous topic - next topic
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Turntable Ground Wire

Hello everybody. I am new to this site and have recently become a turntable enthusiast. I found a beautiful Benjamin Miracord Elac 40a turntable in very good condition. It seems to only have minor problems. One of the problems is that it does not have a ground wire. I was hoping someone could explain where I could attach a ground wire to this turntable. Thanks in advance for any assistance.

Turntable Ground Wire

Reply #1 –
Most likely the turntable has some sort of metal chassis to which all of the metal parts (motor, tone arm support, etc.) are attached. Look for an accessible nut or bolt on the chassis, loosen it enough to slip a spade lug under it, and retighten. The ground wire should be attached to the spade lug and, at the other end, to the case of the reciver/amplifier/computer that the audio connects to.

Edit: I should have asked first if either or both the turntable and whatever the audio cables connect to have grounded plugs. In the special case where both have grounded plugs you do NOT want to connect a ground wire between them, just make sure that they are both plugged into the same circuit.

Turntable Ground Wire

Reply #2 –
Quote from: pdq on
Most likely the turntable has some sort of metal chassis to which all of the metal parts (motor, tone arm support, etc.) are attached. Look for an accessible nut or bolt on the chassis, loosen it enough to slip a spade lug under it, and retighten. The ground wire should be attached to the spade lug and, at the other end, to the case of the reciver/amplifier/computer that the audio connects to.

Edit: I should have asked first if either or both the turntable and whatever the audio cables connect to have grounded plugs. In the special case where both have grounded plugs you do NOT want to connect a ground wire between them, just make sure that they are both plugged into the same circuit.



PDQ: Thanks for the quick response. No neither the turntable nor the receiver have grounded plugs. The receiver has a small knurled nut at the back to attach the ground. So it is as simple as attaching a wire with a spade lug to an accessible nut or bolt?  I thought I was going to have to solder a wire to something. I have a cheap old Kenwood TT which I took apart to see how they attached the ground wire. That wasn't helpful though because it has several small circuit boards and the ground was soldered to one of those. The Elac 40a has no circuit boards. That is one reason why I like it. Thanks again.

Turntable Ground Wire

Reply #3 –
Maybe it doesn't need a ground!

The audio cables are shielded, and of course, the shield connects to ground on the receiver.  That shield-ground should be maintained all the way to the cartridge, and maybe it's connected to the turntable chassis too.

If you don't have a hum problem, I wouldn't worry about it.  But with turntables/preamps you almost always have some hum & hiss, and the only way to know if a ground helps it to try it.
 

Turntable Ground Wire

Reply #4 –
Quote from: DVDdoug on
The audio cables are shielded, and of course, the shield connects to ground on the receiver.  That shield-ground should be maintained all the way to the cartridge, and maybe it's connected to the turntable chassis too.

The problem is that the shields may NOT be connected to the chassis, in which case there could be significant AC on the chassis, capacitively coupled from the motor windings (assuming an AC motor). This could then capacitively couple to the cartridge and the audio signal lines.

I agree that the OP could try it first and if there is no problem then don't do anything, or he could play it safe and add the ground.

Turntable Ground Wire

Reply #5 –
Thanks for the responses. I was curious about whether the RCA plugs are on shielded cables and re-did one just to see. The RCA cables are NOT shielded. This Benjamin Miracord Elac 40a TT is very old. It didn't surprise me that the cables are not shielded. On the other hand it is supposed to be a high quality TT and the cables may not be original (they have chrome metal plugs with yellow shrink wrap). I always opt for playing it safe especially when it is relatively easy to do so. Therefore I will add a ground.

Turntable Ground Wire

Reply #6 –
It's not necessarily playing it "safe" - there are situations where adding a ground could make the sound worse, or create a potential hazard.


I have a turntable + amp where the ground only works properly if you connect it to the shield of RCA plugs - if you connect it to the grounding plug provided, it's not nearly so effective (audible hum).

So, experiment.

Cheers,
David.

Turntable Ground Wire

Reply #7 –
2Bdecided: Thanks for the reply. How can it create a potential hazard?  How can I make sure it won't? I finally got the TT back to work and it sounds much, much better than before. Also, this turntable does not have shielded RCA cables. I took one of the plugs apart to see. Someone told me that these turntables are grounded through the AC plug but this plug is not a three prong grounded plug and is connected under the chassis only to positive and negative wires. So I installed a ground wire as PDQ suggested. It sounds great and nothing has blown up or caught fire.

Turntable Ground Wire

Reply #8 –
Quote from: pdq on
Quote from: DVDdoug on
The audio cables are shielded, and of course, the shield connects to ground on the receiver.  That shield-ground should be maintained all the way to the cartridge, and maybe it's connected to the turntable chassis too.

The problem is that the shields may NOT be connected to the chassis, in which case there could be significant AC on the chassis, capacitively coupled from the motor windings (assuming an AC motor). This could then capacitively couple to the cartridge and the audio signal lines.

I agree that the OP could try it first and if there is no problem then don't do anything, or he could play it safe and add the ground.


I worked on many turntables in the '70s, mostly Duals, BSRs Garrards and many Pioneers and the very rare Benjamin Miracord. The cables from the preamp to the table were always shielded coax but the wires from the RCA connectors to the cartridge were a twisted foursome. The colors were usually red white green and black though some models used blue rather than black. On the Shure cartridges there was usually a removable ground clip to connect the cartridge body (metal shield) to one of the channel ground wires. The turntable deck plate was where the ground wire attached which was then connected to preamp ground.The  best place for that is the actual circuit board mid way between right and left ground inputs rather than the preamp mechanical frame.

G²