USB to SPDIF interfaces - how to evaluate?


I've been reading up on USB/SPDIF interfaces and having a hard time determining what are the right measurements to evaluate and what audibility threshold exists for these measurements.

The linked site from Audiophilleo has some interesting comparisons:

http://www.audiophilleo.com/comparison.aspx

The comparison highlights Phase jitter (in two different frequency bands) and period jitter. Should I be worried about both? Is period jitter below 5 picsoseconds (ps) really audible? Are there other specs that are even more important to the performance of the USB/SPDIF interface?

Why would additional power improve the performance of these interfaces, which is something that is observed regularly in listening evaluations?

Finally, is the price of this jitter reduction about to decline to a very low level as software and hardware experiences the performance improvements regularly seen in the IT industry? (So does this type of equipment fall outside of standard audio equipment economics?)
jult52

Showing 2 responses by realremo

I just came across this thread, interesting no one has commented yet. In general, I have found in my research the following things:
try to use a converter that utilizes two clocks, one for each "family" of sampling frequencies, 44.1kHz and 48kHz. This avoids "clock synthesis," which can cause jitter.
galvanic isolation from the computer's power source is good, this is why so many converters are battery driven or come with wall warts.
There are several techniques to measure jitter, some of which actually cause jitter, so going by specs is risky. There are also several different types of jitter, as you saw on the audiophilleo site, and these can be measured at different points along the signal path, producing different results. Jitter measurements posted by manufacturers can be misleading.
Jitter sounds like high frequency noise, so I've read. I use a Vlink into a PS Audio DL III, and I think the music sounds too bright, so I'm either going to upgrade the speakers or the converter. Haven't decided.
Yes Extravaganza, I am looking at speakers with soft dome tweets. These BX5s were intended to be temporary, and will be relegated to 2nd system in the bedroom eventually. I was coming from B&W 685s, and noticed a distinct change in the mids. At the time, I thought this was a change from the B&W "house sound" to a more neutral BX5 sound, but after upgrading my head unit, upstream weaknesses are being revealed.