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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 3rd November 2011, 12:37 PM   #17461
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by rsdio View Post
Thanks for that link, Scott.

... but ... log3(60dB)? (from page 7)

To borrow an acronym from Thorsten: WTF?

We regularly see log10() for dB ratios, log2() for efficiency with binary processors, and the natural ln(), which is log2.718(), but I've never seen anyone attempt to make practical use of log3() before this paper. 20*log10(2^10) == 60 dB, showing that you need 60 dB attenuation for the AAF before a 10-bit A/D, but how does that lead to log3(60dB)?

Also, I calculate log3(60) as 3.73, not 6.28

What am I missing here?
Don't know, why do physicists and EE's use different scaling on FFT's? I have not read it carefully enough to see.
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Old 3rd November 2011, 12:39 PM   #17462
chrissugar is offline chrissugar  Romania
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Quote:
Originally Posted by Jakob2 View Post
Paul Frindle, Are we Measuring the right Things? Artefact audibility versus measurement
The Measure of Audio, AES UK Conference 1997.

I have to dig deeper in my archive (which suffers in the moment from similar problems as jneutrons), but afair Theile and Wittek should have done some experiments with ITDs in stereophonic presentations, which confirm at least the ~10Ás .

As stated earlier, small head movements actually increase the localization accuracy, investigated a couple of times with good accordance.

BTW, this was an interesting description in last years discussion:

Gearslutz.com - View Single Post - Paul Frindle - Is This Truth Or Myth? -

later on Frindle mentioned differences detectable as low as 4Ás.

I'm glad you mentioned Paul Frindle because it was my intention to mention his work on the SONY OXF-R3 console (which is considered a state of the art digital console costing over 1 million$).

He has a deep understanding of analog and digital and he did some serious research to correlate audibility of various processes.
He discovered that even dither at -110dBFS could be detected in -70dBFS tape noise recorded digitally if in the randomness of the dither there was a partial statistical correlation. Let's not forget that there is no real random in digital computer world, so you have to know how to design a good random generator using limited computing resources.

chrissugar
 
Old 3rd November 2011, 12:41 PM   #17463
ThorstenL is offline ThorstenL  Germany
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Hi,

Quote:
Originally Posted by scott wurcer View Post
Sorry I'm done with this. As John points out the concept of subtractive dither is over 50yr. old in image coding etc.
That is completely besides the point.

So you insist on not showing anything real that relates to how things really work while presenting something that is an idealised version of hos things could be done, but are not. That is your prerogative...

Ciao T
 
Old 3rd November 2011, 12:58 PM   #17464
ThorstenL is offline ThorstenL  Germany
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Hi,

Quote:
Originally Posted by chrissugar View Post
All the discussion about dither being evil is absurd.
Is it? Would you say that applying 14 Bits of worth of dither and converting a 24 Bit PCM Signal to 10 Bit with this is a good idea?

Quote:
Originally Posted by chrissugar View Post
Dither is absolutely necessary to avoid distortion that would appear if high bit depth files would be simply truncated to 16bit.
Just because you say so does not make it so.

You are aware of Ethan Wienders tests?

Grekim and Ethan test dither, jitter, A/D

Quote:
Originally Posted by chrissugar View Post
It is very simple to experiment by generating a 24bit sine wave in some proaudio software (Wavelab) and truncate it to 16bits and also dither it to 16bits. Just do an analysis and also listen. You can draw your conclusions.

For music the truncated version will sound distorted and all the low level information like space cues and reverb tails will be lost while the dithered version will retain all the low level information and no distortion.
Funnily enough, that is not what I hear and what for example Gremkin/Wiener found.

And note, I do take umbrage as such with 2LSB dither applied to the 16 Bit CD Release when coming from a 24 Bit Master (though the actual need for said is debatable), but I do take issue with 16384 LSB Dither applied to a 24 Bit signal...

Ciao T
 
Old 3rd November 2011, 12:59 PM   #17465
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by ThorstenL View Post
Hi,

BTW, how about you show instead the simulation of a real system, instead of making up stuff that we still have not even a feasibility analysis for. I mean someone may mistake what you posted for an actual illustration of what actual dither does in an actual 16 Bit System...

It is actually already quite obvious in your pictures...


I missed the return to the condecending tone. What I presented was text book stuff. I would think converters used to master CD's are a bit better than off the shelf and their INL and DNL are pretty close to ideal, in any case things are much better now. If you sent a complete map of the INL and DNL of your particular A/D or D/A it could be simulated, but no I don't have time.

As for the harping on FFT's, ideal TPDF dither produces uniformly distributed white noise as a residual, the spectra are not interesting on any scale. Text book stuff again.

Quote:
No need to use real DAC's, all this can be done using "idealised" converters and in something like Mathlab. I lack the time to set this up.
Why am I not surprised? It's either that or someone else paid for it so it's proprietary. Gee when I use "idealized" converters it's not OK.
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Last edited by scott wurcer; 3rd November 2011 at 01:04 PM.
 
Old 3rd November 2011, 01:03 PM   #17466
SY is offline SY  United States
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John Curl's Blowtorch preamplifier part II
Quote:
Originally Posted by Jakob2 View Post
as cited before, Paul Frindle reported in his Convention paper ABX-Results for an impressive list of small differences (done in studios) including a constant halfsample width delay of one channel (leads to ~11Ás) and confirmed it later several times in discussions over at the pgm list.

Paul Frindle, Are we Measuring the right Things? Artefact audibility versus measurement
The Measure of Audio, AES UK Conference 1997.

later on Frindle mentioned differences detectable as low as 4Ás.
I have that paper. He lists a bunch of things that he claims are audible, but neither references the tests nor (for the ones he did) gives any detail whatever on how the tests were done and what precisely was being tested. It's an entertaining document, much of it is useful, but it's rather short on data. I wouldn't be citing it as evidence that a 10us interchannel time delay is audible on speakers.

I do note with amusement that he says several times that the quality of the equipment used in evaluations isn't very important as long as level and frequency response variations are controlled.
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Old 3rd November 2011, 01:04 PM   #17467
chrissugar is offline chrissugar  Romania
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Quote:
Originally Posted by ThorstenL View Post
Hi,



That is completely besides the point.

So you insist on not showing anything real that relates to how things really work while presenting something that is an idealised version of hos things could be done, but are not. That is your prerogative...

Ciao T

You insist on some claims that have no ground in theory and in practice.
My (and many others) measurements and listening tests on real equipment correlate very well with the theory so there is no gap between the two world.

Also all the measurements and listening tests done by Dan Lavry and Paul Frindle are not some theoretical simulations but results with real converters and processors.

here is a small excerpt from Dan's paper:
"Dithered signals provide a "constant" noise floor, independent from signal and DC offset.
Measuring a triangular dither with a "dB meter" shows a reading of -93 dB for 16 bits. The energy
density (at each frequency) is at about -125 dB. Can you hear under the noise floor? You can hear
30dB below your "meter", all the way down to the noise density in the surrounding frequencies.
Reexamination of the frequency plots shows that you can hear a 16 bits dithered signal down to about
-125 dB under full scale.
Some manufacturers choose to view the special case of undithered signal gating as a the 16 bits
hearing threshold. One should not confuse the "gating threshold" of unditherd system with the noise
density of a dithered one. The "special gating case with 1/2 LSB of DC" occurs at about -96 dB. The
noise density (per frequency) for dithered signals is almost 30 dB lower.
The ability of the dither "to to bring the gated signal back" is shared by all types of dither.
Rectangular, Nyquist and triangular all perform the task within about 3 dB of each other (a range of
about 1/2 a bit). Beware of claims for "a special ability" of a specific type of dither to provide "3 -4
more bits". The 30 dB or so of dynamic range "beyond" the gating threshold is not unique to one type
of dither. It is shared by all types of dither and is not to be confused for additional bits. The proper
criteria for dither quality is its ability to eliminate distortions and noise modulation."


chrissugar
 
Old 3rd November 2011, 01:09 PM   #17468
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by ThorstenL View Post
You are aware of Ethan Wienders tests?
Did they evaluate the noise of the original? Lots of opportunity to obviate dither.
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Old 3rd November 2011, 01:25 PM   #17469
jneutron is offline jneutron  United States
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Quote:
Originally Posted by SY View Post
I'll reverse the question- delay one channel by 1/12 ms (approximately, whatever TD corresponds to an inch). Any difference from the geometrical move?
Of course not. Humans will adjust to the sweetspot.

Again, Non Sequitur.

jn
 
Old 3rd November 2011, 01:28 PM   #17470
chrissugar is offline chrissugar  Romania
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Quote:
Originally Posted by ThorstenL View Post
Is it? Would you say that applying 14 Bits of worth of dither and converting a 24 Bit PCM Signal to 10 Bit with this is a good idea?
If the final delivery format is 10bit then yes but why we are talking about a limited format.


Quote:
Originally Posted by ThorstenL View Post
You are aware of Ethan Wienders tests?
It is Ethan Winer and yes I'm aware for more than 10 years about all of his demistification. His tests are mostly based on mediocre quality recordings. I'm not surprised he thinks the Creative Sound Blaster is as good as an Apogee converter.
Nobody in the mastering comunity is taking him serious.
I think you should listen to some of the guys who proved their hearing and technical abilities with their work like Keith Johnson, Dan Lavry, Paul Frindle, Bob Katz and many others.


Quote:
Originally Posted by ThorstenL View Post
Funnily enough, that is not what I hear and what for example Gremkin/Wiener found.
I think you are alone because the whole mastering community (you know the guys who deliver all the audiophile music available) think different related to dither.
Dither is not an option in the real world audio.

chrissugar
 

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