Ground loop with Supernait 2

Possibly just adding the second mains earth with the Hicap is showing up a problem elsewhere. Have you got all of the units from the same power strip. What is connected to the Cambridge and what else to the SN2 as you may have another signal  ground to mains ground connection via these. 

PS - are you using the USB input on the Cambridge and if so what is the ground lift switch on this unit set to ?

You may find that if you lift the earth connection of the 851N, then you will stop the loop, because the 851N will get its earth from the SuperNait 2. But there may not be one anyway, see below.

The other possibility is that the SuperNait isn't getting its earth from the Hicap2 DR for some reason. In that case the whole lot might be up in the air, as the 851N may not be earthed at all (double insulated units don't need an earth to be there for safety reasons). I would check the earth connection in the mains lead to the HiCap2 DR. Is it a new unit or a pre-owned one?

best

David

Yes, all three units are in same power strip. There is nothing else connected to the 851N as it is a streamer. A Yamaha receiver pre-out is going into the av bypass on the Supernait but the receiver is only a two prong power cord and there is no noise from that source, it is only when I add the 851N that the noise starts. I'm not using the USB input on the Cambridge Audio 851N, and switching the ground lift switch on that unit has no effect on the noise.

The Hicap 2DR is a used one and it does have a bit of a hum itself.

razman posted:

Yes, all three units are in same power strip. There is nothing else connected to the 851N as it is a streamer. A Yamaha receiver pre-out is going into the av bypass on the Supernait but the receiver is only a two prong power cord and there is no noise from that source, it is only when I add the 851N that the noise starts. I'm not using the USB input on the Cambridge Audio 851N, and switching the ground lift switch on that unit has no effect on the noise.

The Hicap 2DR is a used one and it does have a bit of a hum itself.

If you have the 851N connected but disconnect the AV receiver from the SN2 do you still get the noise. I suspect the earth loop is via this route (via something else like a sat box, cable box, tv connected to the AV receiver) ? 

Haven't tried disconnecting the receiver but will. As I said, all was well until I added Hicap DR. Yes, receiver has cable box, tv, and sub connected to it.

It may be worth undoing the four din plugs for the two snaics connecting the hicap to the SN2, and checking that all the wires are connected to the pins. If everything was fine before the hicap was added then it seems highly possible that the issue is down to either the hicap or the snaics. 

Make sure you turn the SN2 and hicap off at the mains first. 

Adding a Naim CD5X did the same thing in my system.  

As James said, the CDP highlighted a problem caused by my Cable TV service.  I replaced the interconnect between my AVR and NAC pre using a ground-loop isolator interconnect.  Not expensive, very effective.

Nick

Thanks everyone for giving me some ideas of what to try. Nick, can you tell me what ground-loop isolator you used?

Dennis

Radio Shack