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How do you fix electrical interference from motherboard?

Update: I overlooked some stuff on the SMSL M500 and discovered:
1. USB in - RCA out: EMI issue.
2. USB in - XLR out: No Emi.
3. TOSLINK in - RCA/XLR out: No Emi.
4. USB/TOSLINK in - headphone out: No Emi.

The only case when EMI occurs, is when using USB in and RCA out.
So, there is no EMI when using Toslink or XLR or headphone out.

Toslink fixes EMI because:
Toslink is fiber optic and electrical noise and ground loops don’t pass through light.
Headphone out fixes EMI because:
headphone out is less sensitive and less powerful


But why does XLR fix EMI?
 
I got this kind of problem with my audio computer, right after it suffered eletrical damage in all USB 2.0 ports. I can't use the 2.0 ports and only can use the 3.0 spare port. This boring noise change even when I move the mouse.

Note: My USB DAC wont' relay noise through my amp with my laptop!
 
^^^[ime] [computer USB] Better laptops, high-end models, much less likely to have noise on USB than whatever desktop computers, maybe especially DIY builds.

You don't get specs on this stuff - PSU noise, at least not without much searching and comparing and not buying any better/good brand PSU without EMI noise spec. Not easy to check before buying, all people can tell you about is fan noise.

Laptops maybe even more tightly-packed motherboards, maybe forces design eng. to give more attention to isolation and so on.
iow, better/high-end/more expensive laptop less likely to have noise on USB. No absolute rule, but the chances are better.

And DACs, and why some DACs are more expensive, and "implementation makes a difference" ? - Then look for USB isolators, for a start. Apparently not so commonly used.
 
The OP may have called it quits, but I hate unanswered questions.
But why does XLR fix EMI?
Because it wasn't EMI in the first place, but a ground loop at work.

A ground loop makes itself felt every time the common ground potential between two devices differs, as for an unbalanced connection this looks exactly the same as actual signal voltage.

Now the SP200 should generally be sitting at outlet PE potential, given that the current flowing through its very own PE conductor is best described as "sod all". (PE = Protective Earth.)

If you have PC --> USB --> M500, the common ground on the M500 has to go through:
1. USB cable shield
2. Mo/bo ground planes
3. ATX power connector and power supply cables, power supply internal connections
4. IEC power cable PE conductor
(all of generally low but nonzero resistance)
before we finally arrive at the outlet. #1 is shared with DAC power supply, #2 and #3 may be shared with substantial return currents from PSU and GPU supply, and #4 tends to exhibit substantial capacitive coupling to the L and N conductors (e.g. from PSU-internal filtering) so AC components of power supply mains current will have a tendency to couple into it capacitively. The latter issue may actually be present on the SP200 as well but its power supply in general will be much, much smaller.

This leaves us with an AC voltage between M500 ground and SP200 ground. Now establishing a second connection between the two via an audio cable is going to reduce this voltage but not bring it to zero, as the first path is fairly low-resistance to begin with. This should explain why RCA cables with low shield resistance are preferred.

Balanced connections, properly implemented (*cough* AES48-2005 compliance *cough*), care precious little about common-mode voltage differences, just as long as they're within a few volts or so. Shield currents will be flowing past the audio circuitry entirely, which cares only about differential voltage between the two signal conductors. If some voltage appears on both equally as it would here, it cancels out almost entirely (the relevant performance parameter is called common-mode rejection ratio or CMRR, and in this case I would expect about 40-50 dB - which, while not infinite, improves the robustness quite dramatically over the 0 dB of an unbalanced connection). This potentially makes the equipment designer's job a whole lot easier - you can just connect your audio ground to PE and don't have to worry about mains leakage in transformers or mains filters.
 
Buy yourself a Seasonic Prime titanium rated 1000watt power supply and it should make a significant difference or solve your problem….
 
Buy yourself a Seasonic Prime titanium rated 1000watt power supply and it should make a significant difference or solve your problem….
:oops: daaaamm
Seasonic sure give full specs...even... rectifiers, capacitors...Vishay, Hitachi, Infineon... \ graphs and all.
This got me thinking I should build a small desktop computer...
https://seasonic.com/prime-ultra-ti...ec049b45d48-1628847137-0-gqNtZGzNAeKjcnBszQhi

PSUphile cables in a cloth bag :)
1628850873692.png


[All these years of development, and Firefox doesn't do an FTP file for me...?] :confused:


The Cybenetics noise rating LAMBDA A++ rating [fan, etc. SPL. ...
+ there are fanless models
https://www.cybenetics.com/index.php?option=database&params=2,0,12
http://members.cybenetics.report:5050/d/cybenetics_LLm_eu.pdf
 
Buy yourself a Seasonic Prime titanium rated 1000watt power supply and it should make a significant difference or solve your problem….
Much as I love Seasonic as a consistent producer of high quality PSUs (I have 3 different models), they have little to do with this issue. @AnalogSteph explains why briefly in post #44 above, or see Jensen Transformers' application notes - AN007 has an in depth explanation.
[All these years of development, and Firefox doesn't do an FTP file for me...?] :confused:
They gave about a year's notice that they were going to remove ftp support from the browser, and finally removed it in Firefox 90. Reasoning given on their developer google group. It was deprecated in Chrome even earlier, but I don't know if they've actually removed it yet.
 
[...]
They gave about a year's notice that they were going to remove ftp support from the browser, and finally removed it in Firefox 90. Reasoning given on their developer google group. It was deprecated in Chrome even earlier, but I don't know if they've actually removed it yet.
I think it was deprecated generally like >10 years ago, at least. How many times I used it in the last 20 years...[?] ...ok, that 2020, I'm surprised they even bothered that long. I suppose I thought they could somehow just sandbox it or something but now that I actually think of it :) what a waste of time.
Quite odd that Cybenetics do that - when you see a link in a table like that, you expect it to be a pdf.
 
Buy yourself a Seasonic Prime titanium rated 1000watt power supply and it should make a significant difference or solve your problem….

Why would that model power supply help with ground loop, as opposed to OP's previous PSU?
 
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