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USB audio jitter

tomli747

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Dec 6, 2018
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It seems there is no resend when a frame is lost in isochronous mode. What will happen if some samples are missing? Does it cause jitter?
 
Losing a frame would cause a pop or drop out.

Jitter has to do with how consistently the frames are delivered.
 
The vast majority of DACs these days reclock the data so jitter on the USB signal does not matter.

A lot of testing has shown the dropout rate is essentially 0 for home USB links.
 
As Maverickronin has said frame loss will cause dropout and pops. It is not a gradual loss of quality.

Dacs reclock data from USB asychronously. There are some design details that can let a DAC be effected by the USB noise. Smart choice is to buy a good DAC not effected by the issue.
 
Will a poor quality USB cable cause more frame loss and degrade sound quality?
No. Likely the DAC will not work at all. In all my testing, I have run into one such cable I had to throw away. Otherwise as others have said, cheap cables don't cause fidelity issues you can hear.

To force errors I had to string two thin and long USB cables and that is something most people are not doing.
 
No. Likely the DAC will not work at all. In all my testing, I have run into one such cable I had to throw away. Otherwise as others have said, cheap cables don't cause fidelity issues you can hear.

To force errors I had to string two thin and long USB cables and that is something most people are not doing.
Isn't audio over USB very low demand compared to video data ? I remember playing video media from a CD over USB. Isn't the packet bandwidth so high that issues due to jitter are difficult to discover, and never a prevalent problem ?
I am seeing lots of products pedaled claiming to get gains by fixing USB jitter. I also see what are called USB "reclockers" that are built on a fallacy that clock synch are done over some wire in real time across the bus.
I guess the trend is audio jargon will first extrapolate RF principles to the audio spectrum and now this is carried across onto digital packet communication.
I wonder if there is any single publication targeted at expelling all the cooked up myths.
 
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