reclocking

Alfe - that is a shame. I dont believe that most mastering studios realize how important jitter is in the A/D. It is expensive to get low jitter in a A/D and the other devices used, like preamps are critical as well. Most studios dont spend enough for this equipment. This seems to be the trend; lower cost garage studios using computers etc..

Once the jitter is in the master, there is nothing you can do to improve this.

I'm a strong believer in capturing the master on analog tape and mixing it analog. Then digitize it.

At lest the playback jitter we can have an effect on. There seems to be no linits to getting it low enough. Evey time I achieve lower measured jitter, I can hear the improvement. Even the difference in sound quality between 50psec and 25psec. Who would have thought?

Steve N.
Empirical Audio

Steve,

I'm not comlaining about "cheap" USB converters, I complain about ALL USB converters. USB uses packets of data-music is best served via data streams. Pretty simple. No way to get around it.

Cerrot, what matters is the jitter at the point where the data stream is converted to analog. Whether or not the data is packetized when it is transmitted from the source component to the component in which that conversion is performed has no necessary relation to that. And, assuming comparably good implementation of the two approaches, packetized transmission stands a good chance of being better in that respect.

To achieve minimal jitter at the point of D/A conversion the clock used at that point should be independent of the timing of the signal that is transmitted between components. Otherwise performance will be degraded by jitter in the signal provided by the source; by noise, reflections, and waveform degradation occurring in the interface; and by clock extraction circuitry at the receiving end.

Asynchronous processing of packetized data inherently avoids those issues, or at least greatly minimizes them, since the timing of D/A conversion is essentially independent of the timing of the packetized data. Whether or not it may have other issues, depending on the specific implementation, is of course another matter.

Regards,
-- Al

Cerrot, I started this thread to point out that what ever is the technique used to get rid of the jitter at the end the data have to be switched to analog so the heart
of the system is the quality of the D/A converter not the interface.

Cerrot - Almarg is correct. Packetization has no bearing on the jitter in networked or USB systems. Both are buffered and master clock established in the device interface.

The older Adaptive technology relied on the computer clock, so it was deficient is this way. IT could only be improved with local PLL's which are no match for a free-running clock.

Likewise, DACs that have master clocks that are synchronized to an incoming stream are no match for a free-running clock. Jitter will be higher.

Buffering of the data and "pull" protocol combined with a free-running master clock with low jitter is simply the best way to achieve the lowest jitter in digital. See these plots to realize how low it can be:

http://www.audiocircle.com/index.php?topic=116570.0

The plots at the bottom approach the lower limit of jitter using current affordable technology. Most of the jitter is in the 15-18 psec range. You will not find a transport this low.

Steve N.
Empirical Audio