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A challenge to ItemAudio

item said:
I'm happy the original challenge kick-started some action – thanks Crash!.

But the original objective wasn't in line with the central issue being debated. It rocketed in a bit hot and oblique. The point at issue never was: is a T1 'better' than a RPi? Much too parochial. The question is: do bit-perfect transports differ?

The revision lets us take a fair stab at contributing something useful to the big debate. It couldn't be hosted by any of the digital attack dogs for obvious reasons of prejudice.

I didn't suggest Steven for this role, but he is widely known as 'agnostic' re: computer audio, and for having a revealing system. He's conspicuously not featured in the vitriolic recent threads on the subject and has a reputation for open-mindedness – too open-minded for many of you, but in this instance it makes him the most impartial host available.

As for who 'judges', I would say the more the merrier – judging from the tone and integrity of recent posts, I'm expecting some to attend simply to post 'no difference' on every test sheet without even listening . . .
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The question was "Do the PCs you make sound better than standard machines?"

I'll bring the pi. And now that I know I have nothing to lose, you can square up against my htpc as well.

I promise that there are no audio enhancements.
 
item said:
I'm happy the original challenge kick-started some action – thanks Crash!.

But the original objective wasn't in line with the central issue being debated. It rocketed in a bit hot and oblique. The point at issue never was: is a T1 'better' than a RPi? Much too parochial. The question is: do bit-perfect transports differ?

The revision lets us take a fair stab at contributing something useful to the big debate. It couldn't be hosted by any of the digital attack dogs for obvious reasons of prejudice.

I didn't suggest Steven for this role, but he is widely known as 'agnostic' re: computer audio, and for having a revealing system. He's conspicuously not featured in the vitriolic recent threads on the subject and has a reputation for open-mindedness – too open-minded for many of you, but in this instance it makes him the most impartial host available.

As for who 'judges', I would say the more the merrier – judging from the tone and integrity of recent posts, I'm expecting some to attend simply to post 'no difference' on every test sheet without even listening . . .
Click to expand...

The question was "Do the PCs you make sound better than standard machines?"

I'll bring the pi. And now that I know I have nothing to lose, you can square up against my htpc as well.

I promise that there are no audio enhancements.
 
Plutox said:
surely the obvious answer during the 'tutoring' and 'familiarisation' phases is simply to identify the two sources as A and B. This, of course, is exactly the methodology of professionally conducted audio tests (at least as practised by the EBU). The listener is allowed all the time in the world to listen (and switch between) A and B before deciding whether X is A or B.
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Except what you describe is the exact opposite of the relevant ITU-R recommendation, as used by the EBU for critical subjective assessment.

It specifies a long "Familiarization or Training Period" first of up to 3 hours, in which example artefacts are demonstrated so that the listener becomes familiar and so that some listeners may go from low-ability to expert listeners as a result.

In this period and in the test itself, A is always identified as a reference (the test can be described as AXY, where one of X and Y must be assigned as being the reference, and the other is graded on a continuous subjective scale).

The listener must definitely not take all the time in the world - the time must be restricted for listener fatigue - a limit of around 20-30 mins per session is specified. The familiarization period, short test material and recommended 10-15 trials per session help achieve this in practice while still allowing the listener to pace himself.
 
Pandapple, you seem to have some deeper experience in this area of testing. Can you comment on the test (procedure, etc) & the likelihood of it (as currently configured) revealing anything other than a null result?
 
This warming up the listeners malarky is all well and good but it completely misses one very, very important point.

The purveyors of these special, tweaked audiophile computers claim that the benefits are audible under normal listening conditions, since that's how they are usually demonstrated and sold - and never once have I seen any suggestion that listeners require training in order to hear these benefits.

Someone mentions blind listening and suddenly people want pre listening training.

What utter nonsense!
 
I can't vouch for 'people generally', but what I've said is that any subtle change in a system typically takes time to dial into. In real-world scenario, this happens over weeks or months.

In the unrealistic environment of a quickfire blind test, listeners are rushed into recording verdicts in minutes. The least we can do to prepare for that shock is to give them a chance to get familiar with what they're about to attempt to identify blind.

As I said, make a crooked test, and you get crooked answers. The goal here is to mimic as closely as possible a real listening experience, but somehow subtract expectation bias without changing the state of the listener. It can't be done, but we'll try to get as close as possible.

There's been no story change on this, or any wild, unreasonable claims. Whatever the outcome of this little test, posterity will show a great deal of incoherent flapping about and reactionary panic in the 500-odd post preamble to it.
 
Purite Audio said:
What does a transport artefact sound like?
Keith.
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Anything it does that isn't on the recording!

For some notes on jitter listening see:
http://www.audiocircle.com/index.php?topic=98297.0
http://www.positive-feedback.com/Issue43/jitter.htm
http://www.jitter.de/english/soundfr.html

A guiding principle we've found useful when auditioning transports is that 'quiet is good'. By whatever combination of noise reduction and jitter makes the meaningful difference, the net effect is usually a relaxation of transient 'buzz', a better portrayal of a room acoustic, cleaner/lower LF rendition, more air between instruments, soundstage expansion, better micro-resolution, less hash, ever so subtly better micro-resolution. Altogether, a quieter, smoother, 'darker', more natural listen. It sometimes sounds boring at first.
 
Why not listen to Bob Katz on what jitter sounds like which also agrees with Mark's description:
This is a quotation from Bob Katz, well known recording & audio mastering engineer posted here http://www.digido.com/audio-faq/j/jitter-better-sound.html

After an engineer learns to identify the sound of signal-correlated jitter, then you can move on to recognizing the more subtle forms of jitter and finally, can be more prepared to subjectively judge whether one source sounds better than another.

Here are some audible symptoms of jitter that allow us to determine that one source sounds "better" than another with a reasonable degree of scientific backing:


It is well known that jitter degrades stereo image, separation, depth, ambience, dynamic range.
Therefore, when during a listening comparison, comparing source A versus source B (and both have already been proved to be identical bitwise):
  • The source which exhibits greater stereo ambience and depth is the "better" one.
  • The source which exhibits more apparent dynamic range is the "better" one.
  • The source which is less edgy on the high end (most obvious sonic signature of signal correlated jitter) is the "better" one
.
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And a reply:
The better one, and it is better, is also easier to listen to. . . less fatiguing. I would also add to this that the low end just "feels" bigger and more solid. This is perhaps a psychoacoustic affect more than a measurable one. It may be that the combination of a less edgy high end and greater depth and width makes the bass seem better.
All of this makes sense if thought of in terms of timing (that is what we're talking about isn't it ;-]). With minimal jitter nothing is smeared, a note and all its harmonics line up, the sound is more liquid (a term probably from the "audiophile" crowd but one which accurately describes the sound none the less), and images within the soundstage are clearly defined.
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Just to explain something about the term used above "signal-correlated jitter" or "data correlated jitter"

I posted this on another thread where there was confusion about jitter afoot

There are two main types of jitter Random(noise like) & Data-correlated(varies with the data)
Random jitter is fairly benign & adds noise to the signal, Hearing is fairly immune to constant levels of noise, up to a certain level - we can hear through the noise. Just take tape replay as an example! So we are fairly immune to high levels of random jitter - some say up to 100nS.

Data correlated jitter is not like a constant noise source - it varies with the data that is being processed. This type of jitter is much more intrusive as our hearing is much more sensitive to it's varying effects. It causes distortions which are specific to digital & we don't find in analogue sources -so not equivalent to Wow & flutter at all. It causes the edginess that we often associate with digital, which some mistake for extra detail in the sound.

What Peter asked about was probably a post I made when he asked " interesting remark about how Dacs with sophisticated re-clocking add flavour (ok, perhaps not the best analogy), and that dacs without reclocking, could/would sound better when supplied of a "low" jitter source."
Yes, reclocking, done properly, can reduce high levels of jitter (of both types) but only down to a certain level & with the penalty that it converts it into noise (with some variability). If you feed a source with a lower jitter than this threshold level, the reclocking will actually be detrimental to the sound & mask the benefits of the low jitter source!
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Really it's no big deal, if they differ in sound it will be heard sighted or blind, in the few blind tests I have sat in on I have always heard the difference, if there was one, but thats me, others do or don't and thats the problem, people hear things differently or not at all and this causes all sorts of issues with trying to "test scientificly" and why bother, if it's just to satisfy someone elses "rules" please yourself guys because you sure ain't ever going to please them.
They live to argue the toss.
Mr ED.
 
if you're doing an ABX test, A and B should always be known, each and every time, and only the value of 'X' blinded.
 
arthur said:
Scepticism Steven.

And you may one day find that it's an excellent bullshit solvent.

But then again...
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I'm impressed Arthur. You spelt 'scepticism' correctly there with a c and not a k. You aren't such an oaf after all. ;) :)

I wouldn't describe your responses as sceptical though, they are more as though you come out in a rash.

We can add skepticism to the pfm dictionary along with the verb 'loose' meaning the opposite of 'find' not the adjective 'loose' meaning the opposite of 'tight.'

Anyway, back on topic, well almost...

Perspex!
 
jkeny said:
Yes, reclocking, done properly, can reduce high levels of jitter (of both types) but only down to a certain level & with the penalty that it converts it into noise (with some variability). If you feed a source with a lower jitter than this threshold level, the reclocking will actually be detrimental to the sound & mask the benefits of the low jitter source!
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Surely that just depends on the quality of the clock that is used for re-clocking. If it's better than the clocking of the incoming data then you win. If it's worse, you lose. No mysteries there. Get a DAC with a buffer and a very good clock. Film at 11.
 
Steven Toy said:
I'm impressed Arthur. You spelt 'scepticism' correctly there with a c and not a k. You aren't such an oaf after all. ;) :)
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Locke spelt it with a k, and that's good enough for me.

From wikipedia:
"The American spelling, akin to Greek, is the earliest known spelling in English.[187] It was preferred by Fowler, and is used by many Canadians, where it is the earlier form.[188] Sceptic also pre-dates the European settlement of the US, and it follows the French sceptique and Latin scepticus. In the mid-18th century, Dr Johnson's dictionary listed skeptic without comment or alternative, but this form has never been popular in the UK;[189] sceptic, an equal variant in the old Webster's Third (1961), has now become "chiefly British". Australians generally follow the British usage (with the notable exception of the Australian Skeptics). All of these versions are pronounced with a hard "c", though in French that letter is silent and the word is pronounced like septique."

That last sentence is the reason why I prefer it with a k. With c, casual reading produces the expectation of 'tank'. The benefit of k is that pronunciation is less ambiguous. And it's different from the French which is always a good idea.
 
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