reclocking

Steve...where does jitter occur? Is it more likely to come from the transport/music server or from the DAC? Can it be eliminated completely and how would that be done?

Every usb interfaces manufacturer is claiming that his product is the best even the low cost ones.
What async interfaces is doing expect reclocking and why they should do it better than good quality DAC.

I'm just wondering why the industry is just rushing on solution that is not solving
the problem.Asynch is not fixing jitter issue but adding it to the data.

Jitter can't be completely eliminated because it's created at different stages(power supply,flow rate,cables ....).
In CD industry the physical jitter which was called the BLER had limit of 8% to be in red book spec . Jitter is part of digital audio starting from recording studio all the way down to even the best audiophile system you can find out there.

USB is also the poorest interface. Don't un derstand why so many are using it. it is horrible! anything is better than usb!

Steve...where does jitter occur?

Jitter starts at the master clock in the transport or async USB interface. It then just gets worse as it passes through buffers, translators and cables. The DAC receiver may add more or reduce it a bit. The D/A chip generally adds more.

Is it more likely to come from the transport/music server or from the DAC?

Both have contributions. The worst will be the transport or device that contains the master clock.

Can it be eliminated completely and how would that be done?

Cannot be eliminated completely, but it can be reduced to the point where other system noise and distortion is more prevalent. This is not easy though. One must use very low noise fast-responding power supplies for the master clock and the associated circuitry. This results in tight voltage regulation. Likewise, the D/A chip must have very low noise fast-responding regulation on the supply voltages. DACs without upsampling and with good voltage regulation can delivery a very low jitter result. You generally get what you pay for here.

Alfe - the jitter solution is actually fixed with async USB, but it is highly dependent on the implementation. Most are poorly implemented. There are however other pitfalls that are more difficult to overcome, such as the effect of the playback software and audio stack. Most of these disappear when one uses a network-driven solution such as Sonos or SB, but hi-res is the limitation of these right now.

Cerrot - you continuously complain about the SQ of cheap USB converters and poor designs. This is like buying a cheap CD transport and concluding that all transports are garbage.

There are some high-end reviewers such as JA and Steven Stone that use USB converters for their digital references, and for good reason. They outperform everything else.

Steve N.
Empirical Audio

Alfe - you can see some Async USB and reclocker jitter plots here:

http://www.audiocircle.com/index.php?topic=115008.0

Any manufacturer that claims their device (not the clock) delivers 10psec of jitter on S/PDIF are not living on this planet.

Steve N.
Empirical Audio