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grounding

Postby James Sivewright » 08 May 2017 18:38

Equiptment
NAD intergrated amp
phono preamp and separate power supply
thorens 124 mk11 with ortofon om 10 cartridge and stylus : goldring Lenco p77 tontarm
Rega planar 3 with ortofon cartrige and stylus VMS 30 mk11
RCA Switch box to enable switching between 2 turntables
GROUNDING NAD grounded to thorens tone arm;thorens chassis;phono preamp
I get no noise whatsoever when playing the Rega but have a 50 hZ hum at less than half volume on the thorens.
Any suggestions to solve this problem ?
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Re: grounding

Postby fjdaigle » 08 May 2017 19:24

Grounding problems can be very pesky. I'd suggest stripping everything down except for the Thorens and phono preamp. Start there and see if that solves the problem. If you still get a problem at this step, hook the Rega up and see what happens. Add components as you go, testing at every step. Unless the Thorens has a wiring issue, you've introduced a ground loop somewhere and the steps I've suggested are designed to isolate it.
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Re: grounding

Postby analogaudio » 08 May 2017 21:51

It might be worth investigating how the switch box handles the grounds, a ground loop may be being created by the simultaneous connection of both grounds at the same time.
Ted

Technics SL1600mk2, Ortofon VMS30, modified TEAC AH500 as a preamp, Bryston 4B ST amp, Harbeth M40 speakers, all making musical magic :-)
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Re: grounding

Postby fjdaigle » 10 May 2017 03:18

analogaudio wrote:It might be worth investigating how the switch box handles the grounds, a ground loop may be being created by the simultaneous connection of both grounds at the same time.

Yep. I have that in my mind as a possibility too.
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Re: grounding

Postby James Sivewright » 16 May 2017 11:44

that is exactly what has happened. The grounds were joined in the switch box.I separated them using another switch on the ground wires from the 2 tables. Hum disappeared but now I have a lot of noise on touching the tone arm of the Thorens.Once the stylus is placed on the record all is quite. Any idea what may be causing this?
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Re: grounding

Postby mjwraw » 16 May 2017 17:33

Funnily enough I also have that on a much newer Thorens TT (a TD203). I wouldn't say it's bad, but there is a feint hum, (which of course becomes much more noticeable if I turn my amp up full, but then I never listen at more than 30% volume anyway), and the hum gets slightly worse when I touch the tonearm.
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Re: grounding

Postby James Sivewright » 20 Oct 2017 18:07

I put this on vinyl engine in April ths year. I have experimented with different earthing patterns and some time ago have successfully solved the problem.
I grounded the motor to the to the chassis.The tonearm was also grounded to the chassis. The chassis was grounded to the phono preamp and the preamp to my NAD intergrated amplifier. I also connected the power earth to the house earth via a 3 prong plug.
The hum is gone. No noise when touching the tone arm and you can turn up the volume to over 1/2 way and still no noise. The music has definitely benefited from this.
I have posted this as I hope it might help those battling with hum and ground loops.
James
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Re: grounding

Postby James Sivewright » 20 Oct 2017 18:52

Sorry I made a mistake in saying that the tonearm grounding was attached to the chassis. It is in fact the earth at the base of the tonarm post that is grounded to the chassis. The actual earth from the tone arm is connected to the shield of the right hand rca.
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