Jitter reduction, best device?

Jitter is noise in time domain. Jitter produces sidebands at very low levels but audible since not harmonically related to root frequencies. Jitter free sound has more clarity (free of noise).

Many CD were made from poorly digitized tapes and contain A/D converter jitter that cannot be removed.

As for device - Benchmark DAC1 does excellent job with jitter. Its jitter bandwidth of only few Hz translates to about 100dB of jitter suppression at few kHz.

Jitter comes from recording, transport, cable (reflections on impedance boundaries and noise) and DACs clock jitter.

Yes, I'm becoming increasingly aware that jitter is indeed a real threat to digital sound quality.

If you have good ears and a decent DAC and your digital sources sound good compared to other sources, then you're rig probably has a handle on the jitter. If not, then jitter is a likely culprit. You'll probably only know its a problem once its gone.

The best way I know to reduce jitter to the lowest possible levels is to do it internally inside the player/unit where the unit is extracting digital information from a CD/DVD/SACD disc or a hard drive. This is done via a internal clock replacment with a ultra low jitter fine tuned clock. Either by replacing a master clock or clocking that feeds a chip that extracts the information.

If you add in some other "reclocking device" after the fact (ie: outside the box...) you are just bandaiding the problem. Fix the problem at the source, which is the poor jitter/phase noise feeding the DSP chip responsible for all the decoding (a very cheap crystal oscillator). This is accomplished by inducing an ultra low jitter clock signal (stable frequency) to the mix. The results are astonishing!!!! You can now realize the true performance the artists intended! I hope this helps you guys out!

Asi_tek,

That may not be effective in all cases, as I understand it.

For example, in my system, a Roku Soundbridge feeds my DAC via TOSLink. Data is sent to the Roku via wireless connection from my Vista laptop functioning as a music server, where files are ripped to disk from the onboard multformat Pioneer optical drive.

The Roku caches/buffers data in dynamic memory before forwarding to the DAC.

In this case, it is the Roku I believe that provides the clock for the DAC, so I think that (the Roku) is where the accuracy of the clock would matter.

I also concurrently feed the DAC from a Denon CD player/recorder via coax. In this case, the clock on the Denon provides the timing for the DAC I believe.

Prior to introducing the outboard mhdt Paradisea tubed DAC, I just ran the Denon analog output direct into the pre-amp. In this case, the internal DAC was used.

So what about jitter with the various configurations I've used?

Honestly, I have no clue really.

All I know for certain is that since introducing the external tubed DAC, I am hard pressed to hear any sonic artifacts that would indicate that the source is digital and that any articfacts of jitter is audible.

Prior to the outboard DAC, I could clearly hear some things that might typically be attributable to digital and perhaps jitter, specifically, I could hear a subtle wavering in pitch on lengthy notes played by massed strings in many larger scale orchestral recordings that I did not hear on other reference systems I listened to in comparison.

Was the subtle wavering in pitch due to jitter?

I would say maybe but I do not see how.

What I can say for certain is that going to the outboard DAC seemed to resolve the problem.

The thing is that I do not believe the Paradisea does any re-clocking or other special processing to address jitter, as say the BEnchmark DAC supposedly does. So I am hard pressed to conclude that the problem was due to jitter.

Also, many who try the BEnchmark, which supposedly does address jitter, still often complain about a harsh digital sound.

The best thing I can assume here is that assuming the BEnchmark does address jitter, at least the addressable jitter introduced during playback, then maybe it is the crisp transient response possible with digital that irritates some.

Some believe that it is just the inherent limits of resolution of the Redbook format that is the problem but that has neer been an issue for me.

I am very interested in understanding these factors relating to digital rigs better, so please if anyone ca offer me any additional insights, please do!

Mapman,

It sounds like you may be hearing beat frequencies. This is a subtle effect that could come from a number of things - including your room setup and/or listening position. It is, as you say, nearly impossible to be conclusive that any specific audible effect is from jitter. Jitter is a detail that does not necessarily stick out like a sore thumb. The industry continues to argue about the thresholds of its audibilty....