Jitter reduction, best device?

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....

Shadorne,

The description of beat frequencies fits what I heard.

It was very consistent though with many CDs I played even listening in different rooms on different speaks to the same source.

I never heard it in several high end reference systems I listened to at the time.

Changing to the Paradisea from the Denon's built in DAC seemed to end it, so I suspect it was some artifact resulting from the Denon's DAC.

Jitter is a mysterious bugger indeed!

so I suspect it was some artifact resulting from the Denon's DAC.

It can often be subtle but everyone agrees that DAC's do sound different. Whether this is the effect of jitter reduction or simply the result of a different output stage (tubed) or both is nearly impossible to say.

Asi_tek - Upscaling, also called asynchronous resampling is not bandaiding. It is instead (and not on the top) of traditional extraction of data.

In typical CD-player, as far as I know, stream of data coming from the laser has jitter and varying frequency. Phase Lock Loop is used to sync DAC converter clock to average frequency of the data stream. I believe that now they use double PLL to improve response and FIFO buffers to provide more stable DAC clock.

Upscaling reclocks data with asynchronous clock of much higher frequency. Benchmark DAC1 does manipulation of data equivalent to 1 million times oversampling making DAC clock accurate to 5ps. DAC1 also has PLL but very crude and fast - just to get input data.

Typical CD player has some analog circuitry that mutes the output in between tracks or during invalid data. This circuitry is audible according to some users who tried to disable it. Benchmark detects valid signal and does muting in digital transmitter chip.