First, USB cables cannot "sound" different...they either allow the data to pass through error-free or they do not.
An error-prone USB cable would probably also do things like not print your documents properly, or cause bad data to be pulled off your external hard drive.
I am fairly certain that such cables exist, but they are probably the exception (a chair ran over it, or the cat chewed on it, or the connector is damaged, or something like that).
If you truly are hearing a difference between USB cables, it probably means your DAC or USB Converter is WAY too sensitive to the incoming signal and should be replaced immediately.
