Mains loop

[Deleted member 9286]

Hi all

Just looking for a bit of hypothetical advice from some of the experts here really.

If I was concerned about noise from a mains loop being picked up and entering my DACs ground plane, would having the source and DAC on the same power socket (small loop) or putting them on separate wall outlets 5 metres apart (larger loop) in theory provide the least noise. No amp further down the chain is involved.

I won’t go into specifics as it will most likely be opening a can of worms and I probably wouldn’t hear the difference anyway. I just have the option of either and it got me wondering.

Many thanks in advance.

 

[solderdude]

When you are plagued by a groundloop you just need to break it at the correct point and in the correct way.
This way you can make it disappear or drop below an audible threshold.

The real problem is that it takes effort and time to investigate and use the proper measures.

In most cases the PC-USB connection is the most problematic one and can be broken in many ways. Some more effective then others.

So you need to disconnect DAC, amp, PC, active speakers, and other connected (mains fed) devices and start re-connecting things step-wise and see when trouble starts.
Then look for possible cures.

There is no standard cure, mains filters and safety ground, extension cords, other groups can all make things worse or better.

succes.

 

[Deleted member 9286]

Thanks @solderdude I appreciate your input.

Maybe I should be more specific after all as I guess this is slightly different to a usual setup.

The loop in question is being created between a Chord M Scaler and a Chord TT2. The loop is via the mains connections and the dual BNC cables that connect the two components together.

The reason I ask the question re. short loops vs long loops is because Rob Watts (the designer) has stated that the large FPGA in the M Scaler does generate rf noise at around 2ghz and despite his efforts and treatment, it can make its way into the TT2 ground plane and become audible, unless one of the items is battery powered, therefore breaking the loop entirely. I don’t want to faff with a battery and Rob himself has said it’s not a huge issue.

I’ve mentioned a mains loop rather than a ground loop as I believe both power supplies are not grounded.

Now I know the first thoughts of people here will likely be “it’s probably not audible, so don’t worry” and you are probably correct, I just have the option of a small loop or a large loop and just wondered if one might be more beneficial than the other, given I have the choice.

Thanks

 

[solderdude]

When there is no audible issue then any possible issues are below audible thresholds so no harm is done.
If Chord stuff that is supposed to be connected would have such problems then I would expect them to ensure there is galvanic separation where needed.
HF loops 'cut' through transformers (in common mode) like through butter so isolation transformers will do nothing unless they are accompanied with proper mains filtering. 2GHz can be filtered quite effectively both in common and differential mode.

 

[March Audio]

I'm unconvinced by the loop theory. RF is insidious and can potentially find it's way through via multiple coupling methods.

Considering Rob Watts thinks you can hear things going on at - 300dB I'm not sure I would take the audibility too seriously.

Anyway there is a simple solution. Try both methods but get an assistant to swap them over making sure you don't know which is which. If you can consistently find a preference for one then you have your answer.

My guess is the result will be random.

 

[Deleted member 9286]

@solderdude @March Audio Thanks both for your quick and helpful responses.