What does Jitter sound like?

Shadorne,

Many decades ago my doctoral and post doc training was in psychoacoustics, particularly binaural processing. The concept of "critical bands" refers to a limitation of the resolution of the auditory system and the interaction of auditory stimuli. Needless to say, I take much of the claimed auditory observations with a grain of salt. Many theoretical differences that justify large expenditures do not conform with auditory reality.

From a telelogical perspective, our auditory system must be generalizer, otherwise it wouldn't serve us well. So of course explanations of the sound of jitter will be vague. After all, how many angels can dance on the head of a pin?

db

Dgarretson: great example of a controlled experiment. I wonder how much the improved clock circuitry reduced radiated emmisions, reduced injected noise into the ground planes, vs the degree it reduced actual clock jitter.
I'll always have a hard time understanding why nanoseconds of clock skew difference matter in most modern cd digital receiver front ends. I mean the digital data is clocked off the substrate then buffered (fifo) in the main cd dsp; inside this dsp, a new clock is generated and sent across the interface to the DAC. This buffer is pretty much crucial to good cdp function. I don't understand how jitter, as long as the set up and hold times of the actual registers are met, can be any kind of problem. I have never done a clock mod; do they instruct the modder to cut the (typical) crystal clock osc and insert the new clock signal there? is this only one point or do they also handle the clock to the actual DAC.

Another key feature to modern cd dsp chips is that the actual word (or frame) is entirely jitter free. Perhaps one could argue if the jitter is so horribly poor that individual bits are mis-sampled as they are clocked into the DSP, (then the overall value of the word is off), but that would have be a seriously poor design. Personally too much marketing emphasis is placed on jitter, I feel. The standard approach by all high end cd player designs is to implement an off the shelf DSP device (the thing that sits very close to the spinning disc and is responsible for servo, and data sampling, as well as microcontroller interface) and an off the shelf DAC. Some play games intermediate stages to decouple clocks and reduce skew, but in the end it's really just designing with building blocks that have existed since the 80s. Jitter is one aspect to all this but I think its contribution to the overall distortion spectrum is very miniscule w.r.t. all the other links in chain from pits and bits to volts.
I don't doubt that anyone hears a difference from a mod, but it's hard to distinguish between REAL differences and perceived ones based on expectations (after all the time effort and money went into it there better be a difference right?!). Anyway these are my personal experiences. It's all good fun.

Needless to say, I take much of the claimed auditory observations with a grain of salt. Many theoretical differences that justify large expenditures do not conform with auditory reality.

Agree 100%! Large expenditures do NOT conform with auditory reality. This is why mildy compressed Mp3/AAC can sound pretty damn good or indistinguishable from uncompressed music!!

So of course explanations of the sound of jitter will be vague. After all, how many angels can dance on the head of a pin?

I agree again. However I would suggest that any audiophiles that claim to have seen Angels dancing (on a pin or otherwise) are not to be trusted concerning their other audio observations - especially when it comes to incredible claims of miracle improvements from their tweaks and/or upgrades.

The SCD-1 is different from some CDPs, insofar as a Synchronous Time Accuracy Controller (S-TACT) chip that is located next to DAC in the analog section of the player, isolates master-clock generation and signal voltage-pulse generation in one chip at a remove from noise propagated by high-speed operations in the RF & digital sections. The stock quartz oscillator chip is located in the analog section 1" from the S-TACT. In a clock upgrade the stock oscillator chip is removed & replaced by a lead-out to a 45Mhz clock PCB. To eliminate the possibility of noise induced by capacitive effects across the PCB, I lifted Xin pin of the S-TACT from the PCB and made short ptp connections between Xin & clock PCB. So in view of Sony's set-up that theoretically isolates master clock from digital noise, I am inclined to consider that audible improvement may be largely due to accuracy of the replacement clock.

I've heard audible improvements upgrading power to clock, and also after upgrading power and various passive SMD components around DSPs, PLLs, and motor/servo in the digital section. Whether this is due to reduced jitter or to reduction of other noise I cannot say. But I have no doubt that improvements in the digital domain other than clock are audible as well.

Esoteric sells an optional out-board clock for its top player that's accurate to a half part per billion; magazine reviewers claimed to hear a difference. I know a fellow in Japan who makes similar claims using an external pro signal generator to clock his player.

All this might sound like an exercise in diminishing returns but my ears tell me otherwise.

Shadorne,
I know what you mean. There is a point after which it really is just a silly excess. I've had just as much emotional involvement with my music through the years of upgrades, as I do with my car system. ALl the upgrades have never changed my response to my favorite music. For me I have come to the full realization that it has (always)been more about a fascination/obsession with awesome hardware than as "the" medium to profound musical enjoyment. I have acheived what I think is a great "sound" but I could hear "Blue Sky" (ABB) or Beethoven's "Ode to Joy" on an AM radio and get just as passionate about it, as I do on a high dollar system.
I would argue that 99.99% of the audiogon community is also motivated by the same hardware obsession (why else are you here,eh?). Sure there is something to sitting in the sweet spot, in your space but that's all just initial conditions to the hardware equation. But it's all good, as I clearly prefer this to most other money sucking fascinations. TGIF.