Hi guys, I recently build a DAC using the Xingcore U30 as I2S interface. I chose to feed it using a linear PSU regulator which shares the ground with the PSU reg that feeds the DAC itself. Connecting the USB input to my Intel NUC8 triggers the ground loop, which disappears when I disconnect the USB cord. Another fact is that when I connect my laptop in battery mode to the DAC, the ground loop is absent. What could it be? Can you suggest some possible workaround?
Thank you all and regards,
Gaetano.
Thank you all and regards,
Gaetano.
Guys, can someone of you please help me in solving this issue? Any idea I can operate?
Thank you,
Gaetano.
Thank you,
Gaetano.
My 2 cents would be capacitive coupling through the transformer.
Just a sidenote - a metal case, a non-class II transformer with its core mounted to the case, no protection-earth wire. Maybe grounding the screen PE wire of the transformer could help with the coupling.
Just a sidenote - a metal case, a non-class II transformer with its core mounted to the case, no protection-earth wire. Maybe grounding the screen PE wire of the transformer could help with the coupling.
When you say it triggers a ground loop, what do you mean by that? Is it humming, or making some other noise?
Looks like you are powering the USB board from local +5v? For the 3-voltage regulators on your power supply board, are the grounds for each regulator all floating from each other, or are the grounds tied together? If they are floating that's good. However, if the local grounding scheme is okay then it may mean you need to galvanically isolate your USB board from the rest of your dac. Unfortunately you can't do that properly with the USB board you have, since the master clocks are on the USB board.
@phofman
Thank you for your help. To be honest, I posted an early photo of the build. In the final release, I installed an earth safety wire which I ensured to the case and I connected there the trafo shield wire and also the PSU ground (via a thermistor, a CL60, if I remember well). But all this tricks didn't solve the issue.
@Bonsai
Thank you for your kind answer, too! What I mean is that I can clearly hear an humming when I connect the USB input of the DAC with the PC. I can furthermore say that if I introduce in this connection this USB isolator
the hum disappears, but the Xingcore U30 is no more recognized by the PC (while using another I2S interface, a te7022 based, this USB isolator doesn't break the connection). So my thought is that this hum is caused somehow by the connection itself. Do these more infos make you come up with an idea?
Thank you,
Gaetano.
Thank you for your help. To be honest, I posted an early photo of the build. In the final release, I installed an earth safety wire which I ensured to the case and I connected there the trafo shield wire and also the PSU ground (via a thermistor, a CL60, if I remember well). But all this tricks didn't solve the issue.
@Bonsai
Thank you for your kind answer, too! What I mean is that I can clearly hear an humming when I connect the USB input of the DAC with the PC. I can furthermore say that if I introduce in this connection this USB isolator
the hum disappears, but the Xingcore U30 is no more recognized by the PC (while using another I2S interface, a te7022 based, this USB isolator doesn't break the connection). So my thought is that this hum is caused somehow by the connection itself. Do these more infos make you come up with an idea?
Thank you,
Gaetano.
Its probably common mode noise from/through the PC SMPS when connected to the AC line that gets into the USB bus ground. Nothing new here. Its all well known stuff. So are the fixes.
Regarding USB bus isolators, they can cause more problems than they fix. Many don't fully support two-way communications between USB board and PC. Anyway, USB bus is not the right place in the signal chain to do the isolation. Again, this is all old news.
Regarding USB bus isolators, they can cause more problems than they fix. Many don't fully support two-way communications between USB board and PC. Anyway, USB bus is not the right place in the signal chain to do the isolation. Again, this is all old news.
The easiest way is to replace your USB board with a better one. I2SoverUSB is a good one which includes galvanic isolation: http://www.jlsounds.com/i2soverusbFIO.html
A probably even better one, also with galvanic isolation, might be one shown in the following diagram (TWSAFB-XMOS): https://www.thewellaudio.com/twsdac-dsd-se-bndl/
For both of those, each one works best if configured to run from two isolated linear +5v power supplies, each power supply with its own dedicated transformer winding.
A probably even better one, also with galvanic isolation, might be one shown in the following diagram (TWSAFB-XMOS): https://www.thewellaudio.com/twsdac-dsd-se-bndl/
For both of those, each one works best if configured to run from two isolated linear +5v power supplies, each power supply with its own dedicated transformer winding.
Last edited:
An I2S isolator is quite a bit cheaper than the I2SoverUSB.
https://www.aliexpress.com/i/3256804345904732.html?
https://www.aliexpress.com/i/3256804345904732.html?
I tried a USB isolator from Topping. What a waste of time and money that turned out to be. Here are links to what happened:
https://www.diyaudio.com/community/threads/problematic-usb-isolator-unit.399247/post-7356655
https://www.diyaudio.com/community/threads/problematic-usb-isolator-unit.399247/post-7356710
...BTW, that whole thread may be of interest.
https://www.diyaudio.com/community/threads/problematic-usb-isolator-unit.399247/post-7356655
https://www.diyaudio.com/community/threads/problematic-usb-isolator-unit.399247/post-7356710
...BTW, that whole thread may be of interest.
Last edited:
I think it might also help to fix the wiring/layout.
Connect the AC socket ground to the chassis along with the transformer screen. Isolate the individual boards from the chassis (plastic standoffs) if their mounting holes are connected to PCB ground, then connect system to chassis ground at one single point, maybe even through a "loop breaker".
Connect the AC socket ground to the chassis along with the transformer screen. Isolate the individual boards from the chassis (plastic standoffs) if their mounting holes are connected to PCB ground, then connect system to chassis ground at one single point, maybe even through a "loop breaker".
Exactly the right kind of things to be thinking about. Grounding has to be carefully designed.
I already did it, but it didn't solve the issue. Connected AC socket to chassis, at the same point the trafo shield and the PSU ground through a CL60, but no results, hum still present.
What if I built an USB cable with broken Vcc and ground connections? Only data? Could it work?
Gae
No need to make a new USB cable.
Just remove the item labeled "0" to the left of the USB adapter connector.
Or/AND unsolder the corresponding pin (+5V) on the USB connector
Just remove the item labeled "0" to the left of the USB adapter connector.
Or/AND unsolder the corresponding pin (+5V) on the USB connector
Maybe you use USB2.0 Full Speed isolator, not High Speed?
TE7022 is USB2.0 Full Speed device, working in UAC1.
Xingcore is USB2.0 High Speed device, working in UAC2, and probably does not have AUDIO_CLASS_FALLBACK feature (to wok also in UAC1).
Alex.
If you spend enough on a good USB isolator, apparently there are ones that work properly. Maybe this:
https://hifimediy.com/product/inton...3Wt6fmFMUrw4Uw-NoKg1nno1oz5THR2MaAl4HEALw_wcB
https://6moons.com/audioreviews2/intona/1.html
However, it costs more than I2SoverUSB. May cost more than this other USB board too: https://www.thewellaudio.com/twsafb-xmos/
https://hifimediy.com/product/inton...3Wt6fmFMUrw4Uw-NoKg1nno1oz5THR2MaAl4HEALw_wcB
https://6moons.com/audioreviews2/intona/1.html
However, it costs more than I2SoverUSB. May cost more than this other USB board too: https://www.thewellaudio.com/twsafb-xmos/
Thank you Mark, for your interest, you all are really kind guys!! To be honest, this stuff is really interesting, but unluckily too much expensive for me! What I intend to do is rather to try to isolate the PC ground from the DAC ground using a data only USB cable, cutting black and red wires in the cable and see what happens. If it'll work then I'll be ok, otherwise I'll try buying an hi speed USB isolator like this
https://a.aliexpress.com/_EuIallT
which is much less expensive and I think could work with the Xingcore U30.
Regards,
Gae.
https://a.aliexpress.com/_EuIallT
which is much less expensive and I think could work with the Xingcore U30.
Regards,
Gae.
I already linked to an inexpensive I2S isolator. Not sure why you continue to focus on USB.
Also, you have a loop area with the separate grounds from the same supply to the DAC and Amanero boards...
Also, you have a loop area with the separate grounds from the same supply to the DAC and Amanero boards...
Attachments
Last edited:
@theAnonymous1
To be honest, I didn't pay attention to your suggestion of I2S isolator, sorry. It could be an interesting, cheap and alternative way to face the problem, thank you!
Gaetano.
To be honest, I didn't pay attention to your suggestion of I2S isolator, sorry. It could be an interesting, cheap and alternative way to face the problem, thank you!
Gaetano.