I2S isolation for DAC

I am currently working on a USB DAC project as a part of a headphone amplifier. My idea is to use the AK4493 as my DAC and the Amanero Combo384 as my USB to I2S interface for the DAC.

I am afraid to have some kind of ground-loop or noise introduced from my PC which is why i am considering a galvanic isolation somewhere between the PC and my DAC chip.

Amanero recommend the use of an ISO7640 4ch 150MHz isolator. But their solution does not let the masterclock pass through the isolator.

Would it be a solution to change the chip form a 4ch to a 5ch to let the masterclock pass through, or will the isolator introduce more problems than it solves when used for the about 22MHz masterclock?

Or should I drop the isolation and go for an entirely different way to minimize noise and ground-loops originating form the PC side of the USB interface?
 

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It seems like the AckoDAC card is pretty similar to my suggested solution, except that it has the reclocking feature added. The isolation itself seems to be a 200MHz version of the chip I have already looked at.
When that is said then for 189$ I should be able to make a reclock circuit cheaper.

The I2SolverUSB seems to be a newer version of the Combo384. The board seems similar and the features is the same except for the added support for 768kHz. But the issue is the same for that board regarding isolation.
 
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One thing i am still not sure of, is if this isolation is even needed. I see a lot of high end DAC configurations where the USB input is not isolated at all.
How common is the issue with noise being transmittet from the USB input making it all the way to the analog outputs of a dac?

The entire reason for my fear of noise form the source originates form my old headphone project where i got a ton of 100hz noise from my phone if i plugged in the charging cable whole the amplifier was grounded.
 
Why don't you simply try it? I think isolation is entirely optional and even slightly detrimental to sound quality if there is no reclocking on the clean side. The noise in question depends on the particular pc but is usually not something directly audible as it is above the audibility range.
 
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You will get some additional jitter.

The ideal way is to have the clock on the DAC side and send it to the USB part through an isolator.

If your USB interrface has a clean clock, you might get an OK solution by using a transformer for the MCLK and isolators for the other signals. With most DAC's only the MCLK is critical in terms of jitter.
 
EXAU21 used isolators for MCK without reclocking. Weirdly it was one of the best sounding USB boards i have owned. If not mistaken the isolators were IL715 (100ps jitter).
 

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