I found X9 only has 2 cores and a shielding and that the USB cable has four cores for connection, two for DC power and the other two for signal. Did you use double X9 to do the job? one for DC power, the other for signal and leave the two shieldings blank in connection?
Usually, the silver plated OCC cables should be more sharp or brilliant than the pure OCC cables in sonic characteristic. I wonder why you said the pure copper cables would have higher frequency response than the OCC with silver plated ones.