How can ground loops not be a problem in single-ended connections?

[Sokel]

A computer running on different wall socket can sound like something is going to explode.

It wasn't there before connecting the converter thought.
Something went wrong with it probably.

 

[antcollinet]

If there is little or no magnetic or electrostatically coupled noise to pick up, it is a non-problem.

Exactly - for a ground loop to be a problem, there not only has to be a loop - there has to be a source of noise current to flow around the loop. And ground impedances have to be such that they flow around the loop, rather than down the mains connection to ground.

Then those loop currents need to be sufficient to create an audible voltage along the analogue interconnect.

 

[antcollinet]

That does not sound like a ground loop. Every ground loop I heard is a constant tone (constant low frequency and volume). This sounds like a bad connection, a broken electronic circuit or an electronic circuit picking up radio frequencies.

I would try to connect the equipment without that convertor board in between. Just use an RCA to XLR converter, which probably is good enough.

You can't tell from listening if it is a ground loop or not. Common ground loop noise is a mains frequency hum simply because it is always a potential source of magnetic pickup into the loop. However, in PC audio situations it can also be (for example) graphics card noise coupling into the loop. This can be high frequncy, noise that comes and goes depending on what is being sent to the screen. You can even hear mouse movement in this case.

I do agree though that that sounds like a faulty connection - or to me, more like a noisy volume potentiometer.

Does the noise change if you move the volume control on the preamp?

 

[antcollinet]

So get this:

My preamp only has single ended outs, and it was connected to an unbalanced amp using RCA cables. With zero ground loops. In fact I went through several amps and preamps (all unbalanced) with no ground loops.

Now I got a balanced amp and connected it to my unbalanced preamp with regular RCA to XLR cables - no ground loop.

Then I got this transparent converter to convert the unbalanced outs to true balanced - https://orchardaudio.com/product/rca-to-xlr-converter-module/

And now that it's balanced - I'm getting ground loops.

Everything is plugged into the same outlet/strip, and I'm using a high quality power supply for the converter (I tried several power supplies).

So what can I do?

Important to point out also:

Balanced connections do not stop a ground loop. But balanced interconnect are immune to the common mode noise that results.

The converter you've purchased will still conduct ground noise currents through any loop that exists. And the RCA interconnect from your source to the converter will still be susceptible to picking up the noise.

Oh, and that converter is ridiculously over priced. Likely this item would do just as good a job:

KMTech 2-Channel DRV134 based Differential Balanced Line Driver converter | eBay

Manufacturer: KMTech Design (UK). A high performance, stereo, low noise unbalanced-to-balanced adapter by KMTech Design. However if your priority is sound quality and value for money, then look no further!

www.ebay.co.uk

 

[Geert]

You can't tell from listening if it is a ground loop or not. Common ground loop noise is a mains frequency hum simply because it is always a potential source of magnetic pickup into the loop. However, in PC audio situations it can also be (for example) graphics card noise coupling into the loop.

I'm making an educated guess, that's all we can do. You're right about the PC scenario, but no PC was mentioned here. Instead the system worked fine before switching to balanced and inserting a convertor board.

 

[somebodyelse]

If the braided shield of your balanced cables is connected at both ends you can still have ground loops depending on the design of the power amplifiers inputs and power supply (known as a 'pin 1 problem'). The standard way to solve this quick and easy is to cut the shield connection in the XLR connectors at the source end (the female connectors, a technique known as 'ground lift').

The standard way is to cut the shield connection at the receiving end, not at the source end. See https://www.jensen-transformers.com/application-notes/ AN007 section 3.6 for why.

 

[Geert]

The standard way is to cut the shield connection at the receiving end, not at the source end. See https://www.jensen-transformers.com/application-notes/ AN007 section 3.6 for why.

There is no standard, only preferences. Which end to cut/connect is an ongoing discussion. Most important is to standardize it within your own system. The explanation of Jensen is probably valid (no time to read it now, but it might have to do with better noise rejection), but in practice there are a al lot of very big systems which do it the other way around to assure that when the cable is unplugged at the source the cable is still shielded and does not become a large antenna.

So do as you like, and take care for inputs/outputs (like that convertor PCB) which maybe have already 1 shield end disconnected (which results in both ends disconnected if you cut the other side).

 

[Megaken]

You can't tell from listening if it is a ground loop or not. Common ground loop noise is a mains frequency hum simply because it is always a potential source of magnetic pickup into the loop. However, in PC audio situations it can also be (for example) graphics card noise coupling into the loop. This can be high frequncy, noise that comes and goes depending on what is being sent to the screen. You can even hear mouse movement in this case.

I do agree though that that sounds like a faulty connection - or to me, more like a noisy volume potentiometer.

Does the noise change if you move the volume control on the preamp?

Nope. Even if I completely turn it off. It's coming from the amp+adapter combo. Without the adapter the amp and everything else is black background quiet even at max volume.

 

[Megaken]

I'm making an educated guess, that's all we can do. You're right about the PC scenario, but no PC was mentioned here. Instead the system worked fine before switching to balanced and inserting a convertor board.

I don't have a PC or a TV. Without the adapter same system is completely quiet.

 

[antcollinet]

Nope. Even if I completely turn it off. It's coming from the amp+adapter combo. Without the adapter the amp and everything else is black background quiet even at max volume.

Try making sure the RCA end of the adapter has a good earth/ground.

 

[Geert]

Nope. Even if I completely turn it off. It's coming from the amp+adapter combo. Without the adapter the amp and everything else is black background quiet even at max volume.

So you might be trying to solve a non existing problem. What is the distance between the preamp and power amplifiers?

 

[Megaken]

So you might be trying to solve a non existing problem. What is the distance between the preamp and power amplifiers?

Mmm 3-4 inches.. they're standing on top of each other with a DAC in between but all are separated with spikes

 

[Geert]

Mmm 3-4 inches.. they're standing on top of each other with a DAC in between but all are separated with spikes

Than I simply wouldn't bother about a balanced connection, just use RCA TO XLR cables.

And if its still about trying to understand what's going on with the converter board, cut the cable braids at one end (pin 1) to get the split ground system you were after.

And about the converter board; I see it has a gain of 8dB. That explains why it's louder as you said. As the board is external, it also means it amplifies the noise on the RCA cables. So unless you can dial back the volume on your power amps, that board might not improve performance even it it wasn't making unwanted noise.