DACs: Difference Between Synchronous and Asynchronous?

Can anyone explain the difference and which one sounds better? Supposedly Synchronous sounds better but I don't know why or what the difference is.

Thanks.

 

Assuming you're talking about USB input DACs..

The synchronous interface 'pushes' the data. The computer is in control of what is sent, and the DAC has to re-clock it and sort it out for conversion. It's the first and easiest to implement type.

The asynchronous interface 'pulls' the data. The DAC generates a clock and tells the computer when to send it. The DAC is in control. Requires latest OS/special drivers. Latest and presumably better interface.

Each have their proponents. In general, the async version can run higher bitrates.

 

Can you go into a little more detail on this as I'm not quite understanding why that would be so?

 

It's been my understanding that an asynchronous USB DAC is preferable as it will result in less jitter. See, e.g., http://www.hifi-advice.com/USB-synchronous-asynchronous-info.html

 

Besides less jitter getting the Bit rate the way it is on the HD is the biggest plus va synchronous USB. Once you get a couple 24 Bit files you notice the differences immediately - no contest - asynchronous rules !

 

24 is bit depth. I guess you meant 88/96/176/192kHz sampling rates (with 24-bit word length the last 2 will require computer's USB class 2.0 ports & drivers and a USB DAC with 24/192 input support).

 

Thanks guys!

 

So if not using USB (ie. using an optical out to the DAC) the syncrho/asynchro issue is moot?

 

That's correct.

 

I just got a synchronous DAC and that's why I was wondering. The asynchronous was like $120 more.