What is reclocking in DAC? Is is same as async usb?

Wharfedale EVO4.4 Speaker

anm

Well-Known Member
Joined
Sep 6, 2008
Messages
5,705
Points
113
Location
New Delhi, India
Hi
Came across a couple of dacs, shek and mood lab dice. They claim "re-clocking of input signal to reduce jitter".
Is it a good design? Are these good implementations, even if the design is good? Though implementation is difficult to judge without listening, but some hints are there wrt to components used etc.

Is it same as "async usb" as done by high end DAC (can't recall the name).
Even if it is not same, is it close in SQ?

regards
 

suprateep

New Member
Joined
Mar 2, 2009
Messages
1,097
Points
0
Location
Chicago
Hi
Came across a couple of dacs, shek and mood lab dice. They claim "re-clocking of input signal to reduce jitter".
Is it a good design? Are these good implementations, even if the design is good? Though implementation is difficult to judge without listening, but some hints are there wrt to components used etc.

Is it same as "async usb" as done by high end DAC (can't recall the name).
Even if it is not same, is it close in SQ?

regards

usually what happens is that typically poorly implemented digital analogue connections introduce jitter in the audio streams. If the source has a stable clock and low jitter on output, then it's no problem sync'ing on it but if its not then (no stable clock or poor implementation then) better get a dac with buffer and internal clock.

While I have not come across the DACs you mentioned - many DACs do have a interface to reclock or reduce the incomign jitter before it enters teh DAC.

For more info read this:
SPDIF Reclocking [English]
 

anm

Well-Known Member
Joined
Sep 6, 2008
Messages
5,705
Points
113
Location
New Delhi, India
m-audio 0404 or emu 0404?

regards

Reclocking is basically a process by which incoming data is shifted to a different clock rate. SPDIF interface has no feedback and error correction mechanism, so jitter in the incoming stream leads to clicks and pops. Reclocking resyncs the clock rate of the incoming signal to a (usually fixed) frequency, but sometimes the reclocking mechanisms cause jitter themselves. The Buffalo DAC is an example of a chip that performs reclocking internally, with a very high-quality algorithm. There are specific chips that perform this standalone as well, and require I2S inputs and outputs, but some brands have standalone reclockers as well.

Async USB is totally different. It is a protocol for using the USB connection but a proprietary transmission between a host and a receiver. As you know the USB standard maintains both the electrical and transmission specs. In async USB the port is used as a wire, and the drivers control the flow of data between the host and the receiver. This is allowable only on USB 2.0 and upward systems, and not only high-end cards use it. The m-audio 0404USB is an example of a card that uses this kind of transmission.

This may or may not be followed by reclocking, which is a totally separate process.
 
Top