Quote:
ST is better as it have better clock circuit than STX...it makes ST sounds better.
Read
this.
From the page you linked:
"Fig.15 ASUS Xonar Essence STX, line input, spectrum of 44kHz sinewave at –12dBFS, 24-bit data, 192kHz sample rate (left channel blue, right red; linear frequency scale).
The ST (PCI) version of the Essence didn't measure quite as well as the STX (PCI Express) version, but both still offer very impressive sets of measurements for a product that is a) affordably priced and b) must be housed in the hostile RF environment of a personal "
"Word-clock jitter in the STX's TosLink S/PDIF output, measured directly with the AP SYS2722 and a 44.1kHz datastream, was low at 1.48 nanoseconds, which is close to the system's resolution limit. Jitter in the analog output, assessed with the Miller Audio Research analyzer, was very low at 170 picoseconds left and 186ps right."
So they measured the ST and STX, ST measured worse. Looks like they didn't measure the jitter (which comes from clock circuit) of the ST - but the jitter level of the STX was well below the audible threshold. So it doesn't matter if the ST has less jitter or not.
ST is only better if you NEED to use pci or are going beyond a 2.0/2.1 setup.