converter spec comparison

[dobro]

Issue Six of EQ magazine (why can't they give their magazines month and year designations like everyone else?) contains a wonderfully useful chart that compares major AD/DA converters in terms of their specs (and MSRP as well).

One of the specs they list is "word clock input/output". Some units have a 'no' in that category. How does that work? What clocks the digital signal coming from the converter? Your soundcard? An external clock?

 

[Dolemite]

I saw that issue of EQ whilst browsing the recording mags at Barnes & Noble. The chart was interesting, but the one thing I wanted to see was the actual converter chip used in each unit. I always find it interesting that units varying 5-10 times in price use the same core chipset! They're usually either from Crystal or AKM, BTW.

OK, now to answer your question. The AES/EBU format incorporates clock sync with its data stream, so there is no need for a separate word clock connection. When using SPDIF to transfer digitally when you don't have or don't use word clock, you can often select which unit to use as a "master" and which is the "slave." In this way, the clock signals are not actually transmitted (AFAIK), but the master clock determines the timing of each sample and the slave just locks onto the sample timing coming from the master. Ironically, I believe you can set the receiving unit to be the master...and I'm a little foggy on how this all works out. But in any case, you want the unit that you think has the best clock source to be the master.

 

[dobro]

Okay, so a converter without a word clock in/out would still slave to a good external clock if you had one?

As for the chipset issue, your suspicion is that the improved circuitry in the more expensive units doesn't account for the price differential?

BTW, here's the cheapest converter I've been able to find - 2 channels of AD/DA:

http://digitalaudioworks.com/mimfc241.html

It's sorta reviewed (and favorably) here:

http://www.pcavtech.com/adc-dac/Cow-B/