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

[Zapper]

a] for RCA analog interconnects, use a coax cable with a very heavy braided shield.
b] plug everything into the same AC wall outlet (or better yet the same distribution strip).
c] use short AC cords.
d] chose components that do NOT have plastic insulator rings on their RCA chassis connectors. (this is the same as the XLR "Pin 1 Problem" )
if all else fails:
run a heavy wire from metal chassis to chassis.
* * * * * * * * * *
the idea is to try to get all the chassis's to the same potential.

All good suggestions. I'll add:
e) bundle the power cords together as much as possible to reduce loop area (velcro cables ties)
f) keep analog interconnects short

 

[KSTR]

Interesting. Do you have an example of these?
I have what I think is a ground loop issue. The hum varies with different interconnects, so I‘d like to try the type you suggest

Belden 8281 (dual braided shields) is excellent, 3.6 MilliOhms per meter is hard to beat, it's low cost, still moderately flexible and managable diameter (8mm), and even low capacitance.

 

[Berwhale]

@jdav This thread may be of interest... https://www.audiosciencereview.com/forum/index.php?threads/ground-loops-101.7162/

 

[Sir Sanders Zingmore]

Belden 8281 (dual braided shields) is excellent, 3.6 MilliOhms per meter is hard to beat, it's low cost, still moderately flexible and managable diameter (8mm), and even low capacitance.

All I could find was with BNC connectors. Do you know if anyone sells them with RCA ?

 

[KSTR]

All I could find was with BNC connectors. Do you know if anyone sells them with RCA ?

You're on your own here I fear, or find someone who can solder them for you. There are RCA plugs available which can handle 8mm cable diameter, some are utterly expensive, some are reasonably priced. I seem to recall I have used these in the past for thick cables: https://lautsprecher-technik.com/Co...-End-RCA-Connector-White-Red.html?language=en

 

[Megaken]

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?

 

[Philbo King]

Wow... 200 bucks? Ok then.
Possibilities include being mis-wired, no ground-lift capability, and noisy 9VDC supply.

 

[Geert]

So what can I do

If everything worked fine before, what issue are you trying to solve then?

And are you shure the issue you have now is a ground loop and not just a lousy power supply?

 

[Philbo King]

If everything worked fine before, what issue are you trying to solve then?

And are you shure the issue you have now is a ground loop and not just a lousy power supply?

He switched to a unit with balanced inputs, which reportedly worked fine with simple RCA-XLR cables. It seems the simple answer would be stick with the cables... but maybe he misses the extra 6dB you get by going fully balanced? I don't know.

 

[Geert]

He switched to a unit with balanced inputs

Right, time to go to bed

 

[Megaken]

If everything worked fine before, what issue are you trying to solve then?

And are you shure the issue you have now is a ground loop and not just a lousy power supply?

I tried several power supplies, including one recommended by manufacturer, and a medical grade one.

Not trying to solve an issue just trying to get the most out of the equipment. But mostly just general tinkering and satisfying curiosity

 

[Megaken]

He switched to a unit with balanced inputs, which reportedly worked fine with simple RCA-XLR cables. It seems the simple answer would be stick with the cables... but maybe he misses the extra 6dB you get by going fully balanced? I don't know.

Yes. Part of it was me going from a 150wpc amp to a 400wpc amp (both decent quality) and the output being quieter on the 400wpc amp. I thought maybe something is lost in the unbalanced conversion. It did get significantly louder with the converter device.

But half the time I do things is to test and understand the concept, none of it is mission critical. I would still like to understand where the ground loop is coming from.

 

[Geert]

But half the time I do things is to test and understand the concept, none of it is mission critical. I would still like to understand where the ground loop is coming from.

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').

 

[MaxwellsEq]

Part of it was me going from a 150wpc amp to a 400wpc amp (both decent quality) and the output being quieter on the 400wpc ampy

My guess would be that the gain of the new amplifier is less than the gain of the old amplifier. It would be worth checking the specs

 

[wwenze]

What we call "ground loop" doesn't always mean a physical loop. It just means there is a common-mode voltage difference between the two equipment that is affecting the signal pin and the ground/return/reference pin to a different extent hence eventually causing the noise to become differential.

Careful design can help to reduce this difference. However with balanced equipment, the reference -signal pin already uses the same kind of circuit as the +signal pin so there is little difference between them. Consequently, less care is needed when designing the ground since it is not used as a reference.

The problem comes when you connect that -signal pin to ground on your source.

tl;dr version: A balanced input + a converter can perform worse than a single-ended input that is designed to be single-ended to begin with.

 

[Megaken]

Here's an audio recording of what this sounds like. Is it indeed a ground loop or something else?

Wednesday at 12-41 AM.m4a

drive.google.com

 

[Geert]

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.

 

[solderdude]

Here's an audio recording of what this sounds like. Is it indeed a ground loop or something else?

Wednesday at 12-41 AM.m4a

drive.google.com

Does not sound like a ground loop, that low level hum in the background could be.
You recorded this using a phone while holding the phone ? (explaining the other sounds)
The low level hum heard could also be magnetic induction in cables.
Ground loops usually contain a constant hum which can sound like a low level low frequency hum to a 'sharp' sound with a constant character that disappears when the connection between devices is removed.

 

[Sokel]

Here's an audio recording of what this sounds like. Is it indeed a ground loop or something else?

Wednesday at 12-41 AM.m4a

drive.google.com

That sounds ominous,like something VERY bad is about to happen.
I would disconnect everything and check them for faults (use a DMM or something to check your cables).

There's something very wrong there.

 

[wwenze]

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