What DACs are "reclocking"?


Are there many, many reclocking DACs, or is this particular feature limited to just a few makes and models? Also, how can one tell if a DAC is of the reclocking variety? If the description says something about a low-jitter clock, is that enough, or is that something else entirely? (Yes, I did search the archives -- and Google -- before posting this question.)
Thanks very much.
-- Howard
hodu
"All DACs playing regular Red Book CDs at 96 or 192 KHz (playback clock not an integer multiple of the incoming clock) employ some sort of reclocking."

Not true. Lots of DACs dont upsample and don have any kind of oscillator inside. It's not a requirement.

Steve N.
Empirical Audio
I asked this question because of a post regarding Apple's Airport Express. Poster was told he'd improve things by getting a reclocking DAC. What, I wondered, are those. (I stream to an AE, and have a Cambridge Audio Dacmagic.) Perhaps I should have been more specific in my query. If I'm looking for a better DAC, perhaps even a reclocking DAC, for this setup, what, specifically, should I be on the lookout for?
All DACs playing regular Red Book CDs at 96 or 192 KHz (playback clock not an integer multiple of the incoming clock) employ some sort of reclocking. They employ ASRC (Asynchronous Sample Rate Conversion), which is a good method to reduce jitter. ASRC doesn't totally eliminate jitter, though.
A safe bet as far as reclocking goes are the asynchronous USB DACs. Here the internal clock of the DAC is the master clock, and the transport is slaved to the DAC, its clock is not recovered by the DAC at all.
ESS Sabre DAC chip is said to have a very good internal jitter elimination section for S/PDIF inputs, where the incoming samples are "time-aligned" and picked up at the internal clock's pace.
Any Dac that asynchronously upsamples is reclocking using an internal oscillator. You can also reclock the datastream using an external reclocker and feed any DAC with this.

I personally dont like the sound of any commercially available hardware upsamplers, so I use non-upsampling DACs. Good upsampling software like Wave Editor/Izotope or Adobe Audition will beat the hardware upsamplers.

Steve N.
Empirical Audio
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