Computer Audio Asylum

Posted by audioengr (M) on February 22, 2008 at 10:40:38

In Reply to: RE: USB isolation hub (Gordon, audioengr, John - input wanted) posted by pryamomimo on February 22, 2008 at 07:59:59

The inductor may help in your situation, but it really does not provide isolation, only attenuation of high-frequencies. Listening tests required. As for the hub "reclocking", it is certainly possible, but doubtful. It is more likely that it buffers and clocks the data through a flip-flop. This is a far-cry from useful reclocking. The jitter will still be there and get worse.

Isolation can be achieved using an RF or inductive coupling device. These are active devices. One could also use a pulse transformer, but the USB interface may need DC to operate properly. These will break the ground connection between the computer and the audio system - galvanic isolation.

I chose to isolate further down the chain, in the I2S interface or the S/PDIF output interface.

Steve N.

Edits: 02/22/08

• RE: USB isolation hub (Gordon, audioengr, John - input wanted) - pryamomimo 00:42:25 02/23/08 (1)
  In Reply to: RE: USB isolation hub (Gordon, audioengr, John - input wanted) posted by audioengr on February 22, 2008 at 10:40:38

  Thanks for your comment, Steve. Could you just elaborate a little on this "flip-flop" part?
  
  

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  • RE: USB isolation hub (Gordon, audioengr, John - input wanted) - audioengr 10:56:22 02/23/08 (0)
    In Reply to: RE: USB isolation hub (Gordon, audioengr, John - input wanted) posted by pryamomimo on February 23, 2008 at 00:42:25

    Flip-flop is a fundamental element of synchronous logic. It stores the state of a single bit. If the clock is recovered from the USB stream, then this clock can be used to clock the data bits through the flip-flop and then the stream can be re-encoded and re-transmitted. Not sure if this is what the device you have is doing, but possible. When you reclock this way, it can improve the edges by speeding them up, but it will not improve the timing. The jitter still gets worse as you put the stream through more stages of buffering or clocking.
    
    Steve N.
    
    

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