Willie wrote:
"Asynchronous USB interfaces are not sensitive to the quality of the USB cable.
I have personally experienced better USB cables do make a discernible difference i.e. in my system!"
It is true that Async eliminates the problem of jitter from the computer getting into the master clock of the Async interface, however there are other mechanisms that can still cause jitter due to the USB computer interface and the USB cable.
The main mechanism is common-mode noise. The USB interface is differential, so in theory all that matters in the signal is the difference between the two signal wires. However, in practice any noise on both signals (common-mode noise) is not rejected completely by the Async receiver. Because this noise is not completely rejected, it adds to jitter in the Async interface.
There are a couple of ways to eliminate or reduce this noise:
1) filter the USB interface
2) use a galvanically isolated USB interface
I have solutions for both of these:
1 Short Block
http://www.empiricalaudio.com/products/short-block
2 Power Block
http://www.audiocircle.com/index.php?topic=128620.0
Another mechanism that can cause USB cables to differ is the error rate. It is best to get a high-quality USB cable. Same for S/PDIF coax. Use a high-quality cable there too.
Steve N.
Empirical Audio
"Asynchronous USB interfaces are not sensitive to the quality of the USB cable.
I have personally experienced better USB cables do make a discernible difference i.e. in my system!"
It is true that Async eliminates the problem of jitter from the computer getting into the master clock of the Async interface, however there are other mechanisms that can still cause jitter due to the USB computer interface and the USB cable.
The main mechanism is common-mode noise. The USB interface is differential, so in theory all that matters in the signal is the difference between the two signal wires. However, in practice any noise on both signals (common-mode noise) is not rejected completely by the Async receiver. Because this noise is not completely rejected, it adds to jitter in the Async interface.
There are a couple of ways to eliminate or reduce this noise:
1) filter the USB interface
2) use a galvanically isolated USB interface
I have solutions for both of these:
1 Short Block
http://www.empiricalaudio.com/products/short-block
2 Power Block
http://www.audiocircle.com/index.php?topic=128620.0
Another mechanism that can cause USB cables to differ is the error rate. It is best to get a high-quality USB cable. Same for S/PDIF coax. Use a high-quality cable there too.
Steve N.
Empirical Audio