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Best jitter free USB DAC

Can anyone tell me which of the DACs with USB support have delt with the jitter problem described below?

I cannot decide between the Transporter, SB/DAC1/USB, SB/Brick/USB, SB/Lavry etc. I want to stay in the 2K range.

That is correct. Some of the USB-interface DACs I have measured have ridiculously high jitter. There is also the problem of ground-loops, that affects the performance.

Quote:

Could someone explain to me why this is the case? My understanding is that the USB interface protocol contains error correction and clocking mechanism just like the old serial interface did, whereas the sPDIF does not. So, theoretically, there should be NO jitter at all when going through the USB. What am I missing here?
QUOTE
You're missing the fact that as almost always implemented, the USB interface lacks a high-precision,local clock to control the remote DAC. This is because, again as almost always implemented, the DAC does not communicate back to the USB data source to control the flow of data.

As I understand it, the USB spec does include the possibility of implementing bidirectional communication so that the DAC clock can become the system master clock, but no-one has yet done that. If they do, the DAC clock can now be a high-precision VCXO rather than the usually sloppy PLL, with a significant reduction in jitter.

I'll try to find some references for you to study.

John Atkinson
Editor, Stereophile
dbk
dbk OP
44 posts
 
So steve, which is the best sounding DAC of those listed...e.g.

Stello DA100 USB-D/A Converter
Benchmark DAC 1/USB
Transporter
Wavelength Brick/USB
Lavry DAC
dbk OP
44 posts
 
Steve, are you suggesting then that the Transporter which uses a wireless network has the lowest jitter??
audioengr
3,282 posts
 
"Steve, how does the I2S fit into the above considerations?"

I2S is a means to keep the jitter low once you have a low-jitter signal. Creating S/PDIF again just adds jitter back in. Therefore, if you can stay I2S, the total jitter result will be lower. The Pace-Car for instance ONLY outputs I2S.
audioengr
3,282 posts
 
"So steve, which is the best sounding DAC of those listed...e.g.

Stello DA100 USB-D/A Converter
Benchmark DAC 1/USB
Transporter
Wavelength Brick/USB
Lavry DAC"

The Benchmark DAC-1 USB is the best sounding stock DAC in the list IMO due to the excellent firmware in the USB interface, with the Lavry as a close second provided it is driven from an Off-Ramp or similar low-jitter converter.
audioengr
3,282 posts
 
"Steve, are you suggesting then that the Transporter which uses a wireless network has the lowest jitter??"

No, I'm suggesting that the potential for lower jitter exists with these types of devices. It's all in the parts selection and the design implementation whether this is actually achieved.
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