Resolving Ground Loops? from Multiple Sources
Posted by: John on 28 December 2001
I was originally under the understanding from NANA that the P9 power supply will generate a lot of noise in my system and I should plug it in a separate socket. After a lot of playing around thinking initially I had a stand issue I discovered that to get the best out of my P9 I needed to plug the power supply in my main power bar and unplug my CDS1 from my 52. The results are significant! Is this normal? It seems strange to have a very expensive preamp and being faced with such an issue??? What are my options at resolving this?
Will a Stageline resolve this issue? If so can it be powered by my supercap similar to a prefix setup?
It would be nice to hear from someone at Naim on this as I am sure it effects a lot of people who own Rega decks. If you own a Rega TT try unplugging your other sources.
Any help is appreciated.
John
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Originally posted by John:
From the advise of some people on the forum it sounds like I have a ground loop issue between my CDS1 and P9.
Yes, quite possibly.
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I am running my P9 on the internal boards and I think the P9 is being grounded at my 52.
No, your 52 is grounded by the P9 (and the CDS).
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I understand that my Naim system should be centrally grounded at my Supercap. Correct me if I am wrong.
OK, you're wrong!
No, but seriously, the power supplies do not provide any connection to mains earth. The cable that joins the cartridge to the system is attached to mains earth through the P9's mains plug. The 52 uses this to provide an earth that is then carried throughout all the rest of the system.
quote:
After a lot of playing around thinking initially I had a stand issue I discovered that to get the best out of my P9 I needed to plug the power supply in my main power bar and unplug my CDS1 from my 52. The results are significant! Is this normal? It seems strange to have a very expensive preamp and being faced with such an issue???
In your system the CDS is also earthing the system. All the NACs (except 112) leave all earths attached from all sources. This can give you a ground loop or loops.
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What are my options at resolving this?Will a Stageline resolve this issue?
It is my understanding that the Stageline isolates the 52 from the earth of the P9, which should resolve your issue.
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If so can it be powered by my supercap similar to a prefix setup?
The 52 has two different sockets for input 2:-
If you are powering a Prefix or Stageline from the 52, you must attach the SNAIC-5 to the powered socket (on the right as seen from the back), and use the plastic cap to cover the other one (so you can't accidentally use both). You can just see from the picture that the powered socket provides 24V supplies.
cheers, Martin
I'm not sure if this will help, but here's a picture of the P9 lead connection inside the tonearm of the P9.
I'm not entirely positive of the order of the wires(it's been a while) but it should be, from the 1:00 position White+, Blue-, Black (ground),Green- and Red+. You can see from the photo that the ground connection is brought over to the blue- neutral. So it appears to me that the ground is shared with the blue wire. Seems to me if you stop the contact from the blue- to ground and then leave the ground wire disonnected on your TT there should be no further ground fault. This may pose a saftey issue though and I would suggest that you explore that aspect further.
You can visit this connection on your own turntable fairly easily. Where the fat wire leads on the bottom of the tonearm go in there is a set screw holding the connector in place. Just loosen the set screw and gently pull the whole bit out.
I dispensed with this whole bit as I have the P9 hooked up to a Prefix (K) now, powered by the NAC52/Super.
Prior to this I had a Grado "Reference" MM cartridge on my P9 and it did hum a bit. I was unable to cure the hum. I had been told from several sources that this was common to the Grado's and there was nothing that could be done. Now it seems like there may have been another possible cause.
With the Prefix there is NO hum.
Arthur Bye
