Is computer audio a bust?

10-22-14: Audioengr
Current DACs have difficulty reducing jitter to inaudible levels because this is a difficult engineering challenge, even for seasoned designers. It always has been. The jitter on S/PDIF inputs on DACs is generally reduced somewhat by the receive chip, which uses a PLL to recover the clock from the datastream, but a low jitter input to this receiver chip is still beneficial. Other DAC designs use resampling chips and circuits to establish a new master clock. These can reduce jitter even more than the receiver chip, but there are two downsides: 1) they inpart their own kind of distortion due to way that the resampling algorithm is implemented 2) the new master clock and associated circuitry/power supply adds its own jitter.

Thes best solution for reducing jitter in a DAC is to put a master clock front-end on the DAC. There are two types of these available now, the Async USB interface and the network renderer. Both of these effectively discard the clock in the source computer or device and generate a NEW master clock.
if the power, circuit design and clock selection is optimized, the jitter can be extremely low with these input circuits.

The thing to understand is that these are not easy to design and its really esy for lots of jitter to creep back into the circuit, even if you u a Femtoclock etc..

also, jitter is never reduced to zero as some manufacturers would have you believe.

Jitter when characterized by a single number, such as RMS jitter is an inadequate measurement. Jitter has a spectral component as well as a distribution of amplitude. these are actually more important than any single number to predict if one jitter is more audible than another.

Interesting. In your opinion, is jitter management or the lack thereof the stumbling block to true analog reproduction? Also, what are your thoughts on grounding and jitter production? I know someone in the industry who says a lot of standard grounding schemes are woefully inadequate.

Finally, do you have any thoughts on the software codeveloped by Vertex/Nordost that supposedly measured system jitter? http://www.stereophile.com/rmaf2010/nordost_and_vertex_measurements/index.html

10-23-14: Phusis
It seems this discussion veers into the overly academic. To my mind computer audio is certainly not a bust, on the contrary it's here to stay and to my ears trumps CD-playback (where same CD is ripped to harrdrive) in a pretty obvious fashion

On the contrary, I know quite a few philes who would argue with you after having done both. I have heard computer fronted systems sound like crap even with whizbang dacs and big money ancillary pieces.

"Interesting. In your opinion, is jitter management or the lack thereof the stumbling block to true analog reproduction? "

Absolutely, #1 cause. Also digital filtering is a big offender, #2.

Also, what are your thoughts on grounding and jitter production?

Grounding is a multifaceted issue. There is the issue of earth ground and where this is connected to DC common. This is what star-grounding is used for. Many designers don't understand this. Then there is the issue of ground-return paths. It is generally poor ground return paths that add jitter in most designs. Then there is the issue of the power supply currents in the ground planes and how these affect the signal currents in the ground planes. These can also affect jitter. One must understand the physics of how currents flow in digital systems. This is not intuitive. Creative solutions are required to overcome these issues. This is what sets apart really creative designers from well-schooled designers.

This is a lot like talking about power supplies. Power supplies are only the start of a much more complicated system that I refer to as "power distribution" that exists in all components. Its like saying that Hoover dam creates really clean power, but ignoring all of the transmission-lines and transformers and shared loads that are in between your outlet and Hoover dam.

I applaud any actions like the Vertex/Nordost tools for making better audio measurements. The field has historically been lacking of sufficient measurements to characterize these effects. I have myself tried to do exactly what they are doing, with limited success, when I used to design cables from 1996 to 2000. Correlating analog before and after signals in perfect sync is a difficult task for sure. This demonstrates differences in dynamics, which is the foremost problem with most consumer audio gear. Most gear compresses due to deficiencies in the component power distribution system as well as slow reacting DC power supplies. Cables can also be at fault, but to a lesser degree. More difficult to measure cable effects IME.

Steve N.
Empirical Audio

"If you analyze people's opinions on SQ superiority of WAV versus AIFF or any other format, its a coin toss statistically. What does that tell us?"

Not if you are selective about who does the listening and on what systems. I do these comparisons at virtually every show I exhibit at. The differences are always obvious. Usually the listener that has ripped his entire library in AIFF or FLAC just leaves in disgust because he now knows that he has worked hard to produce something suboptimal.

Steve N.
Empirical Audio

The synchro mesh is not bit perfect. why would you add that before a $4,000 dac? shoot me!