Understanding USB

[opus101]

10 minutes ago, beerandmusic said:

My understandng is that the issue with usb noise is on the 5V bus or pin.

 

My "thinking" is that the two pins for data, even if they had noise on them, that it should be simple to transfer a bit perfect 1s & 0s via those 2 pins. 

I mean all you are looking for on those pins is (ON OR OFF), and any simple design should be able to transfer that data perfectly because you are just looking for a one or a zero and any noise should be able to be filtered very easily.

 

If the 5v is not used in the case of isolation or external 5v circuitry, I do not understand what the issue is?

 

 

A couple of points where it looks like you've not quite understood the issues. Firstly, USB noise is on all the pins of the cable, not just the 5V. And secondly, the noise is nowhere near high enough amplitude to result in digital data becoming flipped.

[opus101]

16 minutes ago, Ralf11 said:

the noise goes to the decode side of the DAC, right???

 

The noise is looking to get back to earth so will go where there's a ground connection. Which normally means the poweramp, via the cables between DAC -> pre and pre-> poweramp.

[opus101]

3 minutes ago, beerandmusic said:

When you say you are exporting an analog signal, Are you sure about that statement?

Do you also suggest when you transfer a data file from your pc to a hard drive, that it is an analog signal?  I believe, but maybe i am mistaken, that it is a binary finle, not an analog file as you suggest.

 

All signals are analog in nature, its the binary interpretation of an analog signal which gives rise to digital.