USB cable hype


Can someone explain the need for expensive USB cables for short runs? The only parameter of concern is impedance. I personally have verified error-free transmission in the Gbps range regardless of cable make/model as long as the cable length is short. There is no magic. It is just about impedance control to minimize loss and jitter. This is inexpensive in the MHz range. I will pay more for a cable that it is well built. I will not pay more for hocus pocus.
axle
Kijanki, I like the Airport Express implementation. I tried AE with both optical and analog outputs. I'm pretty sure that my Meridian G68 processor uses a FIFO buffer with synchronous clocking. Therefore, the AE jitter is transferred. In your case, the clocking is asynchronous and jitter transfer is zero. But even in your case, AE noise can enter the DAC through the analog (but not the optical) cable.

Getting back to my OP about functionality vs SQ. I just received an email from George at ExaSound. Working with George is a pleasure. ExaSound DACs use error correction. Therefore, if it is functioning, it is optimal SQ. This is how it should be. DACs that don't implement error correction and use isochronous transfer mode, have to live with whatever transmission they receive. This is not how it should be. Hence my OP about functionality vs SQ. There are some gray areas, even for digital.

Noise is an additional factor. If a cable introduces source noise or EMI/RF to the DAC, then SQ could be significantly impacted. However, the difference between a bad and good cable is neither a steep nor expensive order.
Axle, I remember from Stereophile test of AE that jitter on analog (jitter artifacts) were much worse (about 5x) than optical out. USB cable that does not use +5V supply for anything should not have it. Also shielding should be as good as possible.
Optical is a good choice. Locate the source far away from the DAC, use an optical cable, and you have no noise. Use an asynchronous DAC with error correction and you have no jitter and no errors.

No noise, no jitter, no errors! What more could you ask for? Too bad optical is SPDIF. I guess there is one more thing to ask for: optical USB.
"No noise, no jitter, no errors! What more could you ask for?" While those are good goals to theoretically try to achieve, I'm sorry to say that in the real world you will never completely eliminate noise, jitter, or errors. You can minimize them by good engineering design. Sorry to be the bearer of bad news, but don't shoot the messenger!