The Absolute Sound "review" of USB cable reads suspiciously like a press releaste

Incidentally, the same kinds of circuits/techniques are used to recover data for high speed data links such as is used on the backbone of the internet. The jitter requirements for those applications are orders of magnitude lower than the needs of audio and although the noise bandwidths are different the issues remain the same, particularly as modulation of the phase and/or modulation of the amplitude is used to increase the data capacity.

“There’s plenty of room for the introduction of timing errors/jitter in that process even if the result is ultimately bit perfect.

“Ideally the DAC will retime the input data to restore a pristine, low jitter, bit perfect, data sequence for conversion to analog.”

>>>In my view the damage is done immediately and irrevocably as soon as the laser reads the data. The primary reasons why the CD playback process is imperfect is due to scattered laser light getting into the detector and vibration of the CD player and CD itself. The nanoscale geometry involved - laser beam width, pit depth distance from laser to the CD metal layer - makes the job of the servo mechanism, especially with all the vibration that is occurring, impossible. You get what you get.

The USB cable argument is probably more similar to the digital cable argument. Or so it would appear.

One other thing that needs clarification- the concepts of bit perfect and low jitter are NOT homomorphic.
Bit perfect simply means that the recovered output data sequence is the same as the original input sequence- which in turn means that the recovered output changes in state are within the correct timing windows.
It tells you nothing about the stochastic and deterministic components of the jitter other than the combination of both in any given timing window does not cause the data to fall outside the recovery region.

Again, the fact that the input sequence is not perfectly timed is not relevant providing the data recovery circuitry/algorithms are able to cope with the imperfections. The use of data corrections (CRCs etc) can ensure bit perfect output sequence results. The use of quality retiming can ensure extremely low jitter prior to the conversion (or indeed during the conversion) to analog.

For high rate data recovery PLLs with jitter in the 100fs region or lower are de rigeur. For audio the best PLLs/DLLs used are sub ps. The theory concerning the eventual SINAD of the data at the output and the resulting impairments is quite clear. There's a reason that digital recording/playback of audio has improved by so much in the last three decades.

Don't you people buy these, as such you should expect your advertising dollar (purchases) being spent in this way!  Why the objections?