Grounding issue with DAC & old amps

[russ74]

I'll try and keep this simple, honest!. I use a simple DIY eBay DAC similar this one here mine has a different transformer & RCA plugs but that's it.All I've done so far is to place the DAC in an old external DVD - ROM case & use as is. I have attached a ground/earth wire to the ac outlet which is crocodile clipped to the case.On both my old amps a green/yellow earth wire is present on the power cord (alongside blue and brown) & I connected them when I fitted plugs. All this is plugged into a belkin surge protector which is also earthed (orange light). When I use the DAC with these older amps I've noticed the led on the DAC fluctuate and cut in & out with resulting sound issues. When I unclip the ground on the DAC the issue goes away so I know its a grounding issue in the system but I'm not sure what I should do & don't really desire to be electrocuted.Just tried it on a modern NAD amp which has no ground in the plug and there are no LED fluctuations or sound issues with the DAC regardless whether the ground is clipped or unclipped.EDIT, I said I'd keep it simple but re-read it & I haven't!. To put it simply do I need a earth/ground cable on the DAC. I.E running from one of these to the case:

Any help will be gratefully received

Cheers Russ

 

[Anonymous]

It is possible that you have the polarity of the mains wires reversed to the amps or the DAC. With UK mains the N wire runs a few volts above Ground so you shouldo only be able to measure a small potential. The L wire runs ~230V above ground. Older equipment is sensetive to which way round you connect the N and L wires. Modern double sheild stuff (with no earth) does not care.

If you have a multimeter try measuring the voltage on the DAC between the Chassis and the Ground Wire. Do the same with both amps.

 

[russ74]

Cheers for the help. I don't have a multimeter to hand, a working one anyway but can pop out and get one tomorrow.I rechecked the plugs on the amps and they are wired as they should be.The DAC transformer has 2 wires, one red (live) and one Black (neutral). The AC socket supplied with the DAC is fused, similar to this one at maplin :

I'll try to explain this as best I can based on the layout in the picture above. Mine has 2 solder pins either side of the fuse, the right one is L and the red wire is attached to this. The left is side is unattached. Directly above this unattached pin is another pin labelled N & the black wire is attached to this. Above this & in the middle is the earth pin where I personally have attached a ground wire which runs to the case.Is this wiring the potential issue?EDIT: Found my ac socket and includes diagrams (bottom right shows the pin layout)Fused AC Socket