First, USB interfaces vary in their jitter. Some are better than others. You should not need a reclocker with a good async USB converter.
Second, no DAC can eliminate jitter. In fact most DACs that reclock with upsampling can actually add jitter compared to a low-jitter USB converter feeding a DAC with no upsampling.
Its all about the quality of the clock and reclocking circuitry. Its like buying a tonearm cardridge. You get what you pay for.
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.
Alfe - you can see some Async USB and reclocker jitter plots here:
Any manufacturer that claims their device (not the clock) delivers 10psec of jitter on S/PDIF are not living on this planet.
Steve...thank you very much for the explanation!
Thank you for your explanation.
I'm disc manufacturer and believe me all the masters that we are getting from studios are disaster when it come to jitter and as we say here in france" the nicest girl of the world can't give more than what she has"
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?
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.
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:
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.
Alfe - you may think that the heart of the digital system is the DAC, but it isn't. It IS the interface that contains the master clock. That can be a built-in USB interface, external USB interface or a device and reclocker.
The problem is that most USB DACs have poor implementations of USB interfaces. The fact that the power and ground of the DAC USB interface shares these resources with other DAC circuitry is bad. This is what makes an external USB converter with a good power supply far superior to the majority of built-in USB interfaces. Just read the reviews. Most of them say that the S/PDIF input performs better than the USB interface.
Steve, I had a blind test in studio today between two set up
M2tech evo stack +burmester DAC 113
direct USB to burmester DAC 113
the source was Mac mini using audirvana
the result was that good quality DAC don't need interface!
But I still believe that for low cost system and badly implemented DACs an interface is the solution.
Alfe - you may need a better converter to beat the USB interface in that DAC. They do exist.
Steve, if they do exist any advise?
Based on the shootouts the best converters are:
1) Off- Ramp 5
2) Diverter HR
3) Berkeley Audio
im using my laptop via usb to my peachtree dac..wireworld usb and using no software just mog on mozilla firefox..how can i improve the quality of music in using mog/spodify etc
if you have Toslink output on your laptop, you could feed this to a reclocker like Synchro-Mesh and then S/PDIF to the DAC rather than USB. Reclocker is around $600 and a good S/PDIF cable $250. 30-day money back makes it a cheap thing to try.
um..i think ill keep it the way it is..will jriver help mog run better within windows?? cant keep spending away..
jriver will not solve jitter issue, you should consider Monarchy dip as recklocker 250$ (150$ used).