Breaking earth loops

[bumpy]

I want to break an earth loop in a signal chain. Do gizmos like this work and what effect if any do they have on sound quality.
Thanks


https://transparent-uk.com/c2g-stereo-audio-isolation-transformer-black-80449.html?mkwid=s_dc|pcrid|44074791843|pkw||pmt|&mh_keyword=&bnine=true&gclid=Cj0KCQjw9JzoBRDjARIsAGcdIDXOOSOqGNLawDnvqbqO POHbv9bTnAAWQ_xxMG3CDOg1MAgfZcujKhgaAtYGEALw_wcB26 323

[Stratmangler]

How do you know you have an earth loop?
What are the symptoms you're experiencing?

[bumpy]

How do you know you have an earth loop?
What are the symptoms you're experiencing?

Here is my perspective.

I have very sensitive speakers and sit near field so any hum in the speakers is a significant contribution. I also have a complex interconnect wiring circuit using the output from the main amp to supply a signal via DSP to the base amp. All this has brought about an increase in earth loop hum which I have diagnosed through 55 years of experience.

I have addressed the mains leads to reduce loops and have them all plugged into a single outlet. I wont be lifting any earthing wires.

This leaves me with the signal wires. I believe earth hums are produced by having (small) voltage differences between the earthing points within the system so that a (small) current flows continuously and you have hum which is normally about 50 Hz.


I think the gizmos are 1:1 transformers and will break the continuity between points in the system. I stand to be corrected by those who know better.

[Stratmangler]

Having all of your devices plugged into a single power strip (ie using just one mains outlet from the wall) usually eliminates any ground loops.
However, it isn't always the case.

The bit about DSP is interesting.
You may be noticing noise that the DSP is superimposing over your signal.

Any chance of some pictures to see what you're playing with?

[The Black Adder]

I got around my loop problem by getting a proper earth lift circuit fitted to my pre amp.

Sent from my 9001X using Tapatalk

[Ali Tait]

DSP may be adding some noise. Is the noise coming from both amps?

A 10-100ohm resistor fitted between signal ground and chassis earth in your amps would help, assuming the RCA sockets are isolated from the chassis.

[Ali Tait]

I got around my loop problem by getting a proper earth lift circuit fitted to my pre amp.

Sent from my 9001X using Tapatalk


I’m going to have to do this. I have my Mytek dac feeding NCore amps directly and have a hum problem. So I either fit some earth lift resistors in my passive Tribute AVC pre and use it in the chain or fit some in the XLR-RCA adaptors on the amps.

[bumpy]

First let me say that with all valve amps there is a small amount of hum in sensitive speakers. This is normal.

With the DSP, volume control and ICE amp on and running but with no inputs the base driver is totally silent. With these components in circuit there is earth grounding hum in the base driver. I appreciate that any output hum on the main amp is brought back round to the base amp, but its more than that.

[bumpy]

DSP may be adding some noise. Is the noise coming from both amps?

A 10-100ohm resistor fitted between signal ground and chassis earth in your amps would help, assuming the RCA sockets are isolated from the chassis.

On both my amps the signal earth and mains earth are connected to each other.

[bumpy]

I got around my loop problem by getting a proper earth lift circuit fitted to my pre amp.

Sent from my 9001X using Tapatalk

Thanks, can someone explain what an earth lift is. Thanks

[Ali Tait]

Fitting a resistor on the signal ground “lifts” it from the chassis earth. If you can insert a 10-100 ohm resistor between your signal ground and safety/chassis ground, this will stop the hum if it’s that causing the earth loop.

[bumpy]

Fitting a resistor on the signal ground “lifts” it from the chassis earth. If you can insert a 10-100 ohm resistor between your signal ground and safety/chassis ground, this will stop the hum if it’s that causing the earth loop.

Thanks Ali
I like the idea of putting the earth lift in my passive pre, but it obviously is not plugged in the mains so the case is not earthed.

[Ali Tait]

Will still do the same job though, you just need that bit of resistance in the signal ground, doesn’t matter which end of the cable it’s at.

Yes it would be the same with my pre- a wooden box with Tribute AVC’s inside.

[Lawrence001]

Will still do the same job though, you just need that bit of resistance in the signal ground, doesn’t matter which end of the cable it’s at.

Yes it would be the same with my pre- a wooden box with Tribute AVC’s inside.I'm no expert but I don't understand, as the passive chassis is isolated don't you need the earth lift resistor to be on a component which is earthed to mains. What does lifting it to a small piece of metal achieve?

Sent from my BLN-L21 using Tapatalk

[Ali Tait]

The interconnect is a cable between two components, in this case preamp and amp. It has two wires, one signal, one ground. The point of this earth lift is to add between 10 to 100 ohms to the ground cable to stop the hum. Think about it, it doesn’t matter which end of the wire you put the resistor, if you measure the cable with a multimeter you will get the same ohms reading whichever end you’ve put the resistor in.

Make sense?

[Lawrence001]

'Fraid not, I agree it changes the resistance between the ground at one end and the passive case at the other (which is not earthed), but is the important measure not the resistance between the grounds in each joined component which is still equal to the resistance of the cable?

In fact I don't understand how changing the resistance between grounds eliminates hum anyway, might have to go back to first principles on this...

Sent from my BLN-L21 using Tapatalk

[bumpy]

The interconnect is a cable between two components, in this case preamp and amp. It has two wires, one signal, one ground. The point of this earth lift is to add between 10 to 100 ohms to the ground cable to stop the hum. Think about it, it doesn’t matter which end of the wire you put the resistor, if you measure the cable with a multimeter you will get the same ohms reading whichever end you’ve put the resistor in.

Make sense?

I'm struggling too. If you put a resistor between the ground of the cable and a case that is not connected to earth, then its seems no better than inserting a resistor and dangling the other end in fresh air. :scratch:

[Barry]

A ground loop is just that: a circular conducting loop, which when threaded by an external magnetic field (due perhaps by leakage from a transformer, or from being in close proximity to mains cables) will cause a 50Hz current to flow in it. Increasing the resistance of the loop by inserting a 10R resistor (so called earth 'lift'), will greatly reduce the size of this induced current and hence the effect it will have on the audio circuitry.

[The Black Adder]

Also, using a passive with transformers will also break the earth loop.

I had a passive once which did just that.

Sent from my 9001X using Tapatalk

[Firebottle]

I'm struggling too. If you put a resistor between the ground of the cable and a case that is not connected to earth, then its seems no better than inserting a resistor and dangling the other end in fresh air. :scratch:

I agree, I think Ali is suggesting that the resistor is inserted in the 'ground' connection out to the output sockets.

As far as an earth lift goes in an earthed case system, the extra resistance between the signal ground loop and the earth loop forces any current that is flowing to flow in the earth connections between cases, rather than the signal connections, thus reducing the 50Hz currents to virtually zero.

[Firebottle]

I'm struggling too. If you put a resistor between the ground of the cable and a case that is not connected to earth, then its seems no better than inserting a resistor and dangling the other end in fresh air. :scratch:

I agree, I think Ali is suggesting that the resistor is inserted in the 'ground' connection out to the output sockets.

As far as an earth lift goes in an earthed case system, the extra resistance between the signal ground loop and the earth loop forces any current that is flowing to flow in the earth connections between cases, rather than the signal connections, thus reducing the 50Hz currents to virtually zero.

[bumpy]

I agree, I think Ali is suggesting that the resistor is inserted in the 'ground' connection out to the output sockets.

As far as an earth lift goes in an earthed case system, the extra resistance between the signal ground loop and the earth loop forces any current that is flowing to flow in the earth connections between cases, rather than the signal connections, thus reducing the 50Hz currents to virtually zero.

I think that is clearer !!
Let me try this. If I take a wire from one of the cable earths through a resistor and then to the mains earth is this the same.?

[Barry]

Also, using a passive with transformers will also break the earth loop.

I had a passive once which did just that.

Sent from my 9001X using Tapatalk

Transformers will only provide galvanic isolation, that is isolation from DC. Any alternating current fed to the primary (such as 50Hz mains 'hum' and its harmonics) will be simply transferred to the secondary winding of the transformer.

I once had a mild hum problem with an AV set up. Using a 1:1 transformer did not help. The only cure was to trace the earth loop and break it.

[Yomanze]

I wonder if it’s an interconnect related issue, specifically with how the shields are being grounded.

What interconnects are you using?

[Firebottle]

I think that is clearer !!
Let me try this. If I take a wire from one of the cable earths through a resistor and then to the mains earth is this the same.?

Only providing the cable earth isn't directly connected to mains earth, this is where the 'earth lift' comes in.

[bumpy]

Only providing the cable earth isn't directly connected to mains earth, this is where the 'earth lift' comes in.

Great I'll give that a go. Some googling suggest a capacitor in parallel to the resistor is a good idea. Don't know why?

[Stratmangler]

Great I'll give that a go. Some googling suggest a capacitor in parallel to the resistor is a good idea. Don't know why?

Coz it blocks DC.

[Edward]

At times I've experienced horrendous or minor hum and scratched my head searching for causes, blaming it on earth loops, bad components and all else between. So far as I recall the hums went away by realigning interconnects and speaker cables, often only by a small amount. What I call 'jiggling'. :)

I offer no explanation as to why (I'm not an electronics engineer), just what I found (so far).

caveat: YMMV. :cool:

[bumpy]

I wonder if it’s an interconnect related issue, specifically with how the shields are being grounded.

What interconnects are you using?

I use Klotz cables around the DSP circuit. These are certainly quieter than the Audionote silver cables I used before.

[bumpy]

Coz it blocks DC.

Is this a worthwhile thing to do?

[Stratmangler]

Is this a worthwhile thing to do?

It also acts as a high pass filter for RFI. which is beneficial.

[Ali Tait]

LOL half my post disappeared for some reason, Alan has covered it. I was planning on fitting an earth point on the pre so I could wire cable ground to that via a resistor. A wire can then be taken back to the chassis of the other component.

Whilst looking around last night I came upon these so am getting some to try-

https://www.ebay.co.uk/itm/600-ohm-Ground-or-Earth-loop-buzz-Isolation-transformer-built-into-a-3-pin-XLR/183818181831?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Hopefully that will do the job.

[Stratmangler]

LOL half my post disappeared for some reason, Alan has covered it. I was planning on fitting an earth point on the pre so I could wire cable ground to that via a resistor. A wire can then be taken back to the chassis of the other component.

Whilst looking around last night I came upon these so am getting some to try-

https://www.ebay.co.uk/itm/600-ohm-Ground-or-Earth-loop-buzz-Isolation-transformer-built-into-a-3-pin-XLR/183818181831?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Hopefully that will do the job.

Something like this would provide greater connection flexibility - all flavours at once :)

https://static.bax-shop.es/image/product/37908/153377/9b62bbcc/ART_DTI_1.jpg

[Ali Tait]

Yeah looked at those on Thomann, have enough on the racks as it is lol.

[bumpy]

Something like this would provide greater connection flexibility - all flavours at once :)

https://static.bax-shop.es/image/product/37908/153377/9b62bbcc/ART_DTI_1.jpg



Please update this thread when you have evaluated them. :cool:

[Slawts]

Just a quick thank you.

I had a hum and after reading the comments on this post plugged my pre and power in to my plug board with all my source components instead of in to the wall. Hey presto hum gone or at least insignificant.

It's magic!

[Ali Tait]

Good result. :-)

[Stratmangler]

Please update this thread when you have evaluated them. :cool:

You'll be waiting a hell of a long time for an evaluation from me.
I DON'T have any ground loop issues.
I have on occasion had fun solving ground loop issues on paging amplifiers in offices and the like.

The box shown is just a couple of isolation transformers with paralleled inputs and outputs http://artproaudio.com/product/dti-dual-transformer-isolator/

[Barry]

As I explained elsewhere, an isolating transformer will not necessarily solve a hum problem. Hum is an AC signal of 50Hz (plus harmonics), so will be passed through a transformer. I once had a mild hum problem with some AV gear. I tried a 1:1 transformer - it didn't work. What did work was me tracing an earth loop and breaking it.

[Stratmangler]

As I explained elsewhere, an isolating transformer will not necessarily solve a hum problem. Hum is an AC signal of 50Hz (plus harmonics), so will be passed through a transformer. I once had a mild hum problem with some AV gear. I tried a 1:1 transformer - it didn't work. What did work was me tracing an earth loop and breaking it.

I didn't post the picture of the isolating transformer box as a cure to anything.
I was just showing a bigger, more complete version of the XLR model Ali posted.

The cure is, as you've already pointed out, tracing the loop and then breaking it.

[Barry]

I didn't post the picture of the isolating transformer box as a cure to anything.
I was just showing a bigger, more complete version of the XLR model Ali posted.

The cure is, as you've already pointed out, tracing the loop and then breaking it.

I wasn't criticising the use of an isolation transformer, just pointing out that if mains hum has already got into the signal path, fitting a transformer downstream of the signal is not going to stop it.

If however the mains hum is due to an earth loop, and it is not possible or convenient to fit earth lift resistors, then a 1:1 transformer placed in the signal pathway is a neat way to break the loop. But in adding an extra component into the signal path, the quality of the isolation transformer is important in respect of both frequency and phase bandwidth.

I note the transformer unit is fitted with XLR connectors. I would have thought if using fully balanced interconnects between items having true dual-differential input/outputs, mains hum breakthrough would not be a problem.

[bumpy]

Just realised my computer that controls the miniDSP is plugged in a separate wall socket, so I can sit with it on my lap.

I plugged it in the same place as the other five components and the earth hum has receded again. I think I can live with this ��

Interesting topic. Thanks for your help.

[Stratmangler]

Just realised my computer that controls the miniDSP is plugged in a separate wall socket, so I can sit with it on my lap.

I plugged it in the same place as the other five components and the earth hum has receded again. I think I can live with this ��

Interesting topic. Thanks for your help.

Laptop?

[bumpy]

Laptop?

Yes the computer holds the program that controls the DSP in the bass circuit. Once the parameters are cemented I can power it with a 5 volt linear power supply.

[Stratmangler]

There is no mains ground continuity from the machine to the plug in the board.
So there can't be a ground loop there.

If plugging the laptop PSU has quietened things down then it's a good move, but I'd be bothered that a SMPS PSU was plugged into the same power block as the rest of my gear.
Sticking a ferrite clamp us close to where the power cord plugs into the laptop PSU would reduce the effects of switching noise (aka RFI).
We humans can't hear it, but amplification devices see it, and they're adversely affected by it.

[Light Dependant Resistor]

There is no mains ground continuity from the machine to the plug in the board.
So there can't be a ground loop there.

With mains connected equipment it is a safety requirement, that the chassis including its top and bottom side front and back metal work
have access to safety ground. http://sound.whsites.net/articles/mains-safety.htm Whilst double insulation creates a different set of
requirements, the majority of equipment requires chassis to be firmly connected to safety earth.

Light Dependent Resistors happen to work exceptionally well to stop ground loop issues in audio equipment, having the side benefit
of improving signal to noise ratio, and as a result the appreciation of music. An article here explores transistor based opto isolators
that also have the same benefit : https://saaubi.people.wm.edu/TeachingWebPages/Physics351_Fall2009/Week8/Chapter8_OptoIsolation_GroundLoops.pdf

[Stratmangler]

With mains connected equipment it is a safety requirement, that the chassis including its top and bottom side front and back metal work
have access to safety ground. http://sound.whsites.net/articles/mains-safety.htm Whilst double insulation creates a different set of
requirements, the majority of equipment requires chassis to be firmly connected to safety earth.

Light Dependent Resistors happen to work exceptionally well to stop ground loop issues in audio equipment, having the side benefit
of improving signal to noise ratio, and as a result the appreciation of music. An article here explores transistor based opto isolators
that also have the same benefit : https://saaubi.people.wm.edu/TeachingWebPages/Physics351_Fall2009/Week8/Chapter8_OptoIsolation_GroundLoops.pdf

It's a laptop computer.
It's double insulated.