best way to connect pc to dac

Sorry, but things are never this simple.

Common-mode noise on the USB interface and cable can easily induce noise in the receiving system, resulting in more jitter. This does happen, because USB interfaces sound better with common-mode noise fixes like filters and galvanic isolation. Ground-loop noise will further exacerbate this. This effect happens even though there is some common-mode noise rejection by the differential signaling on the USB cable. These receivers are never perfect. Also, the edge-rates of the USB signals can affect the receivers slew-rate, which can impact jitter.

I am only talking about jitter, not data corruption here.

Steve N.

Empirical Audio

Jitter is the variability in the timing of the presentation of each new data bit or word as presented to the D/A circuit/chip for conversion. These bits/words ideally are presented to the D/A at precise time intervals depending on the sample-rate of the data stream. These time intervals are all equal over a long period of time, but from one to the next, these intervals vary. They are only precise over a long period such as seconds. The more the time intervals vary, the more distortion is introduced into the D/A conversion. This is jitter. Just like errors in the voltage can introduce distortion, short-term errors in the timing can introduce distortion.

D/A conversion comprises several actions:

1) a voltage is generated based on a data word

2) a timing of the presentation of that voltage is reproduced

3) filtering of the "stairsteps’ in time that result

Steve N.

Empirical Audio

Steve N., are you saying that the "noise" carried by the USB cable corrupts the bits that the "receiving system" decodes, or are you saying the noise enters in to the "Receiving system", bypasses the decoding function (because the USB interface only accepts bits), and then rejoins the signal at some point and ultimately corrupts the analog signal being output? If the latter, doesn't any "receiving system" fall prey to this pitfall from any media source?

No corruption of bits occurs.  The noise that is induced on the receiving system results in noise on power supplies and ground planes, which changes the timing of the logic, resulting in distortion in the D/A conversion.

Steve N.

Empirical Audio