[BrianM]

So, to me the discussion of jitter is a bit of a non-starter.  I personally believe it's an important design consideration but I equally believe a low-jitter setup could sound like crap.  Trying to get our heads around what makes good digital sound is a natural inquiry but focusing on a single element is like trying to pull grapes out of wine.

I agree it'd be a shame if people's notion of a good DAC got reduced to its so-called jitter immunity.  (What about dishing the oversampling rate, the single- versus multi-bit and all that?)  I personally have no idea if my own DAC has any kind of "jitter control."  What I do know is that it's apparently the only 16-bit R2R around, which I'm guessing has a lot more to do with the sound than whatever its jitter characteristics are, not to mention the tube hybrid analog stage.  It seems to me that great performance in those areas could easily render the jitter issue basically moot.  It's about the farthest thing from my mind given the clear, "wet" digital I enjoy now.  Mike, you've referred to your own digital gear being pretty kick-ass, and based on your comments about jitter I'm guessing you're not losing much sleep over it either, whether your gear can claim to "bust" it or not.  I would actually love to learn that my DAC does nothing whatsoever about jitter, because since it's as good a digital sound as I've heard anywhere, that would tell me to forget the whole thing.  But maybe Frank Van Alstine did some reclocking jobbie; I've never read him entering into the details...

[Geardaddy]

Brian, I can attest to the sonic attributes of your DAC.  I actually live in MN and spent time at Frank's Van Alstine's house listening to his gear and also his Salk HT3s.  My wife actually baked him chocolate chip cookies and we listened to music and watched his cats scratch the expensive sound aborbent material on the walls.   Anyway, the Ultra DAC is very clean, open, and smooth and non-digital sounding.  It would be interesting to get his two cents on jitter as he is an engineer and industry veteran and a stellar and straight shooting dude.  

[Freo-1]

The following was Sony's answer to addressing jitter in their reference Home Theater receiver:
 

The design of the interface is exceptional because communicating six
streams of 2.8224 MHz digital samples raises exceptional challenges.
Conveying 1-bit signals at such high data rates and synchronizing the signals
with the receiver's master clock would normally expose the signal to the timebase
errors called jitter. These errors translate directly into time-based distortion
of the audio waveform.
Sony overcame this challenge with the High quality digital Audio
Transmission System (HATS). HATS uses "command-based rate control of
isochronous data flow" to solve the problem. The system incorporates three
principal elements.
1. Variable-speed transmission from the player.
2. Buffer memory in the receiver.
3. Command signals from the receiver to the player, controlling transmission
speed.
With Sony HATS, audio data flows from the player to the receiver's
buffer memory, according to rate control commands from the receiver.
Reproduction in the receiver achieves the full time base accuracy of the
receiver's quartz crystal master clock.
The receiver continually monitors the amount of audio data in its buffer
memory. When the buffer memory reaches its lower limit, the receiver
commands the player to increase data transmission speed. When the buffer
memory reaches its upper limit, the receiver commands the player to decrease
transmission speed. And when the buffer memory is between the upper and
lower limits, the receiver commands the player to transmit at normal speed.
In this way, HATS makes it unnecessary to synchronize a jitter-prone
signal with the receiver master clock. Instead, the buffer memory outputs a jitterfree
signal at the full quartz-crystal accuracy of the receiver's master clock. You
get all the benefits of digital transmission, without the exposing the signal to the
potential for jitter-induced distortion.

While I am a tube guy for general two channel listening, I can tell you that this interface works very well with the Denon 5910 I employ. The sound of the receiver with this input is noticeably better than any of the other inputs to the receiver from the 5910. The entire topology of this amplifier sounds most excellent, and rivals a lot of seperate component setups.

[NewBuyer]

...I did a blind test of my old CDT vs SB3 both feeding via S/PDIF into my old Sony DAC... listening results pointed to a real audible difference...Given that both transports were just passing 1s and 0s to the DAC the differences must have been read errors (by the CDT) or jitter...

Darren, are you sure that read errors or jitter are the only possible alternatives here? For instance I wonder if differences in ground isolation (through the digital cables) could also produce an end-result audible effect, through a mechanism not related to jitter...

[miklorsmith]

Hey, Brian.  My current digital sources are a Lessloss 2004 DAC with clock-slaved Rega transport and an Altmann Attraction DAC that I run on my Red Wine SB3.  I also have a circa 1985 Technics CDP in my living room setup.  They all sound terrific, and all coming from different places.  The Lessloss is an upsampler with synchronous clock, it takes two RCA-connected digital cables to operate.  The signal out from the transport isn't accompanied by a clock signal and the DAC out is also RCA-connected and overrides the clock in the transport.  It's a totally killer setup.

The Altmann is a straight-up nonoversampling DAC which uses a standard digital cable in s/pdif mode with clock and signal getting all comfy cozy.

Depending on mood, tuneage, and other influences I may prefer one or the other.  The Altmann is more relaxed and the Lessloss is all about grabbing bits, though it uses the BB 1704 U-K chip which is a R2R chip which has a bit of a cult following.  It sounds un-digital despite its resolve.  There are more and more machines out there doing a great job walking that line.

My old Technics refuses to die and it actually sounds great.  The living room rig is not "about the sound", it just plays music.  And, it's as easy or easier to get lost in it as the main setup despite a multitude of failings on The Checklist.  C'est la vie and vive le difference.

[darrenyeats]

...I did a blind test of my old CDT vs SB3 both feeding via S/PDIF into my old Sony DAC... listening results pointed to a real audible difference...Given that both transports were just passing 1s and 0s to the DAC the differences must have been read errors (by the CDT) or jitter...

Darren, are you sure that read errors or jitter are the only possible alternatives here? For instance I wonder if differences in ground isolation (through the digital cables) could also produce an end-result audible effect, through a mechanism not related to jitter...

NewBuyer, that is an excellent question! 

Both players were connected to the DAC with identical coax cables at all times (there was an input switch on the DAC) and both were switched on at all times. Actually, both were playing at all times! So in answer to your question, I don't believe that any other factors could account for the sound differences. Any electrical noise via coax or power supplies would have been present at all times.

It should be noted that the results weren't "statistically significant"...but I'm basing my comment on the blind listening impressions (with the one-sided albeit limited score of 4 out of 4 for the SB3 being circumstantial evidence).
Darren

[Ethan Winer]

Darren,

I'm pretty sure it wasn't just in my head since I heard pretty consistent differences blind, and I chose one transport consistently. Given that both transports were just passing 1s and 0s to the DAC the differences must have been read errors (by the CDT) or jitter.

So maybe it was read errors? I'm sure it wasn't jitter, unless one or more of the transports was totally incompetent. Which is not impossible.

--Ethan

[Ethan Winer]

I'd be curious to know what you think might be the reason that different CD-R media sound different to each other and to the original CD they were copied from?  I assume the bits are the same, so the digital part is not the issue.

Yes, and if you play the different media through the same analog path then the analog is the same too. So what does that leave us with? Why, it leaves us with The Answer!

That answer is the frailty of human perception, the placebo effect, sighted bias, expectation bias, and all the other things that cause us to think we hear a change even when no change could possibly exist. That, and of course comb filtering as described HERE.

--Ethan

[Geardaddy]

Here is an interesting snippet from a Stereophile thread pertaining to computer audio, USB, and jitter:

Yes, jitter is a very serious matter with computer audio. In fact, one interesting piece of information we found (though we did not confirm) is that computer manufacturers will ADD JITTER to their clocks for the purpose of spreading the energy across a wider bandwidth to pass emissions testing. Apparently the spike at the fundamental clock frequency was causing interference of some sort.

--------------------
Elias Gwinn
Engineer
Benchmark Media Systems, Inc
www.BenchmarkMedia.com
1-315-437-6300

[Geardaddy]

Same Stereophile thread:

We did measure the audio performance (Freq response, THD, IMD, etc) of the USB input, and it was completely similar to the all other digital inputs of the DAC1 up to 96/24. We also did listening tests. I am continuously conducting this test (as we speak  ), as are several others here at Benchmark. Testing with a CD transport feeding the Coax input, and the computer feeding the USB with the same music, no one has been able to differentiate the two inputs.

--------------------
Elias Gwinn
Engineer
Benchmark Media Systems, Inc
www.BenchmarkMedia.com
1-315-437-6300

[art]

Yes, jitter is a very serious matter with computer audio. In fact, one interesting piece of information we found (though we did not confirm) is that computer manufacturers will ADD JITTER to their clocks for the purpose of spreading the energy across a wider bandwidth to pass emissions testing.

Uh.......we don't call it "jitter"......it is called "spread spectrum", and yes, it is done to reduce peal levels of EMI. The idea is to not maintain a constant carrier frequency. If you modulate it, and move it over a wide enough spectrum, the peak levels are lowered. Same amount of energy, just spread out. And therefore lower in level.

Pat

[mfsoa]

Yes, and if you play the different media through the same analog path then the analog is the same too. So what does that leave us with? Why, it leaves us with The Answer!

That answer is the frailty of human perception, the placebo effect, sighted bias, expectation bias, and all the other things that cause us to think we hear a change even when no change could possibly exist. That, and of course comb filtering as described HERE.

--Ethan

But noone in the room had any idea that I had taken a commercially bought CD, copied it with EAC and burned it onto silver and gold discs. They had no idea what I was putting in the player, or what I was asking them to listen for. They didn't know if the same disc was being put in again and again or not. They didn't know whether we were evaluating demagnetization, anti-static treatment, different pressings of the disc, - Nada

Yet time after time when the gold disc was put in the response was immediate "Yes, that's the one that sounds much better than the others". I would stand to the side and could also hear what the listeners were reporting, so I was experiencing much different comb filtering all the time. Maybe I was giving some hidden clue with my body posture when the gold disc was in, like the horse trainer that cues the horse when to stop pawing the ground when he reaches the right number   Or the two listeners accidentally leaned into the "good" comb filtering spot each time the gold was played.

I dunno. I sure can't say it was jitter reduction. I can't confirm that the data was bit-identical. But the fact that the gold and silver burns sounded different from each other and both betterd the original remains. You cannot say no change existed because you were not there. (I'm in NJ if you are ever in the neighborhood and would like to try to repeat this). Maybe my CD player is the only one succeptible to this?

Instead of the frailty of human perception, maybe this speaks to the absolutely incredible powers of human perception that we sometimes discount too readily.

Thanks, this has been fun. Seriously, I enjoy the different opinions!

-Mike

[miklorsmith]

My introduction to different sounding blanks was at the Genesis speaker factory in Seattle.  Gary Koh was showing a friend and I a stellar $45k pair of speakers and some prototype tube amps.  He said "check this out", and proceeded to play the same cuts on about 4 different burned blanks.  My buddy and I were quite surprised and had the same reactions to the blanks though we had no prior inclinations.  He's a devout disbeliever in these things as an EE.  Gary is the fellow that wrote the "Black CD" paper and got the ball rolling with it.

[Geardaddy]

Yes, and if you play the different media through the same analog path then the analog is the same too. So what does that leave us with? Why, it leaves us with The Answer!

That answer is the frailty of human perception, the placebo effect, sighted bias, expectation bias, and all the other things that cause us to think we hear a change even when no change could possibly exist. That, and of course comb filtering as described HERE.

--Ethan

But noone in the room had any idea that I had taken a commercially bought CD, copied it with EAC and burned it onto silver and gold discs. They had no idea what I was putting in the player, or what I was asking them to listen for. They didn't know if the same disc was being put in again and again or not. They didn't know whether we were evaluating demagnetization, anti-static treatment, different pressings of the disc, - Nada

Yet time after time when the gold disc was put in the response was immediate "Yes, that's the one that sounds much better than the others". I would stand to the side and could also hear what the listeners were reporting, so I was experiencing much different comb filtering all the time. Maybe I was giving some hidden clue with my body posture when the gold disc was in, like the horse trainer that cues the horse when to stop pawing the ground when he reaches the right number   Or the two listeners accidentally leaned into the "good" comb filtering spot each time the gold was played.

I dunno. I sure can't say it was jitter reduction. I can't confirm that the data was bit-identical. But the fact that the gold and silver burns sounded different from each other and both betterd the original remains. You cannot say no change existed because you were not there. (I'm in NJ if you are ever in the neighborhood and would like to try to repeat this). Maybe my CD player is the only one succeptible to this?

Instead of the frailty of human perception, maybe this speaks to the absolutely incredible powers of human perception that we sometimes discount too readily.

Thanks, this has been fun. Seriously, I enjoy the different opinions!

-Mike

Mike, that's a great experiment.  There is obviously something to this.  Some might fuss at you and ask for a higher subject number to provide statistical significance (but I don't think so...).  As far as the frailty of human perception, I straddle the fence.  I agree on the one hand with Ethan about the human mind's propensity towards self-deception, but at the same time it is also an amazing instrument with untapped or unmeasurable abilities.  Regarding the mind's ability to discern sonic differences in different digital formats, Don Hoglund from Granite Audio told me that one of his former design partners could tell differences in digital resolution levels 100% of the time.  This could also speak to the idea that not all ears are created equal or it is something you can train yourself to do....  

[Ethan Winer]

Some might fuss at you and ask for a higher subject number to provide statistical significance

Picture Ethan raising his hand wildly in the air nodding Yes!

And also demanding a true double-blind test. Anything else is guessing. But you're right - I wasn't there so I can't say for sure. Though I bet you all $100 if I was there I'd have been able to solve the riddle.

One thing you might not be aware of is that all CDs have built-in error correction. I don't mean the reconstruction that can happen when a CD is severely compromised. Rather, for every 16 bits of data there are 14 bits of backup data somewhere else on the CD ready to step in at a moment's notice behind the scenes without you knowing. This error correction is not quite as robust as the correction built into data CDs. With data CDs there are 16 bits of redundancy for each 16 bits of data. But audio CD redundancy is not chopped liver. It works, and basically guarantees that what was burned onto the CD is what comes out the DAC.

Folks, when this stuff is tested properly nobody can pick out one from the other. Whether digital cables, CD media, jitter reduction, or whatever. The only tests that "confirm" a difference are casual tests done at audiophile gatherings.

--Ethan

[Geardaddy]

Along those lines:

"We did measure the audio performance (Freq response, THD, IMD, etc) of the USB input, and it was completely similar to the all other digital inputs of the DAC1 up to 96/24. We also did listening tests. I am continuously conducting this test (as we speak ), as are several others here at Benchmark. Testing with a CD transport feeding the Coax input, and the computer feeding the USB with the same music, no one has been able to differentiate the two inputs."
--------------------
Elias Gwinn
Engineer
Benchmark Media Systems, Inc
www.BenchmarkMedia.com

[AphileEarlyAdopter]

  This could also speak to the idea that not all ears are created equal or it is something you can train yourself to do....  

Ofcourse, yes. More than 12 years ago when I bought my first audio equipment, I bought the cheapest one - NAD. Mainly because I could not tell the difference between equipment and did not want to spend on something which obviously I cannot appreciate. Unfortunately, now the "cat has tasted the milk" it costs me money or depression that I cannot spend more money on audio .

[Geardaddy]

AphileEarlyAdopter, I bought my first "system" in middle school with my hard earned $ from the old summer job, and it included a NAD integrated amp.  I loved that thing and for the time (and the $), it sounded quite good.  The rest of the system included Bose 501s (ouch...), and a top of the line Akai tape deck.  I did not enjoy the music any less, but unfortunately, I too have been poisoned....