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Ground loop advice needed

MarcosCh

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Hi,
I had what I think was a ground loop with the following setup:

Power strip > raspberry pi 4 official USB psu > raspberry pi 4 > Motu M4
Same power strip > random USB charger > sound blasters G6 > line out (unbalanced) > Motu M4 (the signal reaches to the G6 via toslink optical)
Motu M4 > balanced > balanced amp

Why do I think it was a ground loop? Because if I power the G6 with a power bank the noise dissapears

Unfortunately i returned the Motu for a different reason unrelated to this but i want to order it again... if i am confident i can find a solution for the ground loop first

I know that I can solve the issue using a balance dac to the Motu, but this is not an economical viable solution for me now.

My questions are:

Would the ground loop dissappear if I power the G6 from the pi the Motu is connected?
I could not test this solution easily because for some reason when I plug the G6 to the pi it screws the pi configuration and I get no sound and I am not knowledgeable enough to make it work. However i could use a charge only usb cable if i find one so that the pi does not see the dac or even take a normal cable and cut the data wires (?)
What are the chances that this works?

Any other suggestions with the existing setup?

Thank you for your advice.
 
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AdamG247

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Here is some good info/advice that may help.

 

JayGilb

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Hi,
I had what I think was a ground loop with the following setup:

Power strip > raspberry pi 4 official USB psi > raspberry pi 4 > Motu M4
Same power strip > random USB charger > sound blasters G6 > line out (unbalanced) > Motu M4 (the signal reaches to the G6 via toslink optical)
Motu M4 > balanced > balanced amp

Why do I think it was a ground loop? Because if I power the G6 with a power bank the noise dissapears

Unfortunately i returned the Motu for a different reason unrelated to this but i want to order it again... if i am confident i can find a solution for the ground loop first

I know that I can solve the issue using a balance dac to the Motu, but this is not an economical viable solution for me now.

My questions are:

Would the ground loop dissappear if I power the G6 from the pi the Motu is connected?
I could not test this solution easily because for some reason when I plug the G6 to the pi it screws the pi configuration and I get no sound and I am not knowledgeable enough to make it work. However i could use a charge only usb cable if i find one so that the pi does not see the dac or even take a normal cable and cut the data wires (?)
What are the chances that this works?

Any other suggestions with the existing setup?

Thank you for your advice.
I'm guessing the pi could not recognize the G6 ID code that was transmitted to it when it was connected.
Maybe a power only (no data connection) usb a to usb c cable would fix this problem. No idea if it would fix the ground noise.
 
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MarcosCh

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Use separate power strips.
Really? So simple? I never thought that would help, but no idea.

@AdamG247 thanks! I watched that one back in the day, very worthy and good learning. Not sure if my understanding of what is said there gives me a clear answer for my problem though :D

@JayGilb thanks for confirming that
 

AdamG247

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Really? So simple? I never thought that would help, but no idea.

@AdamG247 thanks! I watched that one back in the day, very worthy and good learning. Not sure if my understanding of what is said there gives me a clear answer for my problem though :D

@JayGilb thanks for confirming that

Here is another guide from Audioholics that may be more informative in your case. Ground loops can be incredibly frustrating to correct.
 
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MarcosCh

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Gratitude goes to Voodooless for nominating your thread and Amir for approving. I did precious little in the process.

Here is another guide from Audioholics that may be more informative in your case. Ground loops can be incredibly frustrating to correct.
Will read with interest, thanks again!
 

Speedskater

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OK, look at the photo near the bottom of this Audio Precision note:
 

AudiOhm

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Not all power strips are created equal, please tell us the manufacture/model of the power strip.

Take the power strip you have and plug it into a GFCI, you have some in the kitchen and bathroom.

Many cheap/non approved power strips will trip the GFCI, toss it if it does...

Ohms
 
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MarcosCh

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Not all power strips are created equal, please tell us the manufacture/model of the power strip.

Take the power strip you have and plug it into a GFCI, you have some in the kitchen and bathroom.

Many cheap/non approved power strips will trip the GFCI, toss it if it does...

Ohms

I trust ikea stuff sold in germany complies with the standard requirements. Hopefully.
 

wwenze

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Would the ground loop dissappear if I power the G6 from the pi the Motu is connected?

Most likely. You just need a power-only USB cable and hope your pi has enough output current.

Or you can just power both from the same USB hub or something

BTW there is also the possibility that regardless of how you connect the G6, as long as it is powered by a noisy power supply (i.e. many USB chargers) you still get noise on the G6's which is of a differential nature (i.e. not caused by ground loop). Something like this is easy to hear - a USB DAC with headphone output - a differential set-up by nature - being more noisy when powered by a computer vs when powered by a smartphone. This one is easy to verify - Just have the G6 powered by its own power supply with nothing connected and hear the result via headphone. If there is noise then it is entirely the G6's fault.
 
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MarcosCh

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Most likely. You just need a power-only USB cable and hope your pi has enough output current.

Or you can just power both from the same USB hub or something

BTW there is also the possibility that regardless of how you connect the G6, as long as it is powered by a noisy power supply (i.e. many USB chargers) you still get noise on the G6's which is of a differential nature (i.e. not caused by ground loop). Something like this is easy to hear - a USB DAC with headphone output - a differential set-up by nature - being more noisy when powered by a computer vs when powered by a smartphone. This one is easy to verify - Just have the G6 powered by its own power supply with nothing connected and hear the result via headphone. If there is noise then it is entirely the G6's fault.
Great, this would be the easiest solution for me.
To your second comment the G6 does not have battery so you always need an external psu. But i have used it with different ones and never heard a noise, only with the setup described in post #1.
I think i will give the Motu a second chance and cross fingers....
 

Speedskater

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Never heard that before, where can I read up on this?
Keith Armstrong
Jim Brown
Ralph Morrison
Neil Muncy (RIP)
Henry Ott (RIP)
Bill Whitlock

each have written at least 1000 pages. I'm not about to search thru all that.

* * * * * * * * * * * * * * *
The basic idea is to reduce the total length of the Safety Ground wires from audio component to component. This is to hold the potential of all the component chassis's to about the same value. and to reduce the area of the ground loop.
 
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thestraycat

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Hi guys, I'm based in the UK. (only mentioning this due to our power plugs carrying earth!)

This is a good read. However i had a quick question to those in the know as i'm currently wiring up my house. Picked up a 1000ft spool of susplus CAT7 (for £20) and have just started to wire up a comms cab in the loft.

My question is. I've been wiring up the orange cable lengths in the diagram that go between the patch panel and each of my rooms wall plates with S/FTP cable and S/FTP keystones and have bene incorporating the shielding into both ends of the cable as per the instructons of the keystones on both ends. As ou can see in my diagram.

My take on it has always been:
If you've got CAT7 then use it rather than buy CAT6a specifically.
Shielded is totally un-necessary for domestic use in 99.99% of cases
If your cable is shielded cable, then terminate it properly to the keystones in case it acts as an interference conductor and does the opposite of what it was intended.
If the orange cable is successfully screened on both ends then it dosnt matter if you use shielded or unshielded patch cables on the switch and pc ends.

Am i am at risk from ground loops?

Should the purple cables in the diagram be unshielded cables to help break the sheilding at these points?
(Or should i continue using shielded cables between the patch panel + switch and the wall plate and the PC (as per the diagram)

Opinions?


shielded or unshielded.jpg
 
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AnalogSteph

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Literally the only time I can potentially see that making a difference is during a nearby lightning strike (loop area and stuff). From an audio system perspective, all the mains PE and cable shield connections are lumped together. I would go shielded for these connections, you can always add a connector piece and a short unshielded patch cable should the need ever arise.
 

thestraycat

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@AnalogSteph - Thanks for the reply - Just to confirm that i follow.. .your saying:

1. I shouldn't worry about ground loops.
2. Carry on using shielded cable from patch panel > switch
3. Carry on using shielded cable from wall plate > PC....
4. If any issues arise, change one of the cables in point 2 or 3 above to an unshielded cable?

Just trying to get it straight in my head... :)
 
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