I had an old Adcom feeding a DAC, the sound did slowly degrade; not that that is an argument for difference in sounding transports. It just happened is all.
My shameless support of Bybee continues, because they work in my audio system and in others that I have experienced. People are always asking me for audio advice, because I have 50 years in the audio business. I try to help if I have some real input on the specific subject that they are concerned with, and if they don't expect to design something for free for them. That is where I draw the line.
SY,
Here is an old Stereophile article from 1993. Old yes, but would it still apply where jitter is concerned?
A Transport of Delight: CD Transport Jitter | Stereophile.com
Lots of measurements and graphs. I am not an expert when it comes to digital by any means. I only know the basics, and what I have learned from reading.
Jim
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Let's try to look at this from a logical, thinking man's perspective. If you look how data is stored on a CD, you see that there's more bits on it than is required for the audio! More than double! (See the CD Redbook specifications for more detail).
There's the audio data in 96 bits IIRC chunks, there's blocks, frames, preambles, EC sections, parity bits, status bits, timing, what have you. It's a sophisticated storage system that embeds the coded audio as to make it virtually impervious to damage.
It is not unusual for the system (because that is what it is) to have literally thousands (!) of sequential bits, in blocks, damaged because of a scratch, and yet the audio coming out unscated!
The idea that a lowly cable can damage such a robust system is, well, not something I would put money on.
But since we are in thinking mode, let's think a bit further. Let us assume we listen to two CD transports/cables and feel that one has a warmer midrange and the other has more sparkle in the treble. What does that mean for the difference (if it is real) in the digital bitstreams?
It would mean that *something* or *somebody* is very selectably changing a bit here, another bit there, to increase a sample value here, decrease a sample value there, to cause the midrange level to rise or the treble level to decrease. And a cable is doing that? Really? That cable would need to possess more computing power than in the laptop I am typing this on.
The idea is just to ridiculous to seriously entertain.
Yet, you say, when I listen to these two transports and switch between one to the other, I am certain I do here a difference! And I am sure you would be honest and sincere. How can we reconcile this then?
The reason for this state of affairs lies in the way we perceive, in the way we process inputs from all our multiple sensors, remembered history and expectations, and from the mix come up with an opinion. It's not a kind story, but it has been confirmed for centuries really.
Not sure you want to hear more about it, but we can come back to it later.
If you are still in serious/learning/thinking mode, spend a few minutes looking up The McGurk effect, The ambulance color test, and read this:
https://www.harman.com/sites/default/files/white-paper/12/11/2015 - 05:54/files/AudioScience.pdf
forward to page 10, BLIND vs. SIGHTED TESTS – SEEING IS BELIEVING
If you are serious about this, I promise you a quantum leap in understanding! And for free 😉 (OK some time spend).
Jan
There's the audio data in 96 bits IIRC chunks, there's blocks, frames, preambles, EC sections, parity bits, status bits, timing, what have you. It's a sophisticated storage system that embeds the coded audio as to make it virtually impervious to damage.
It is not unusual for the system (because that is what it is) to have literally thousands (!) of sequential bits, in blocks, damaged because of a scratch, and yet the audio coming out unscated!
The idea that a lowly cable can damage such a robust system is, well, not something I would put money on.
But since we are in thinking mode, let's think a bit further. Let us assume we listen to two CD transports/cables and feel that one has a warmer midrange and the other has more sparkle in the treble. What does that mean for the difference (if it is real) in the digital bitstreams?
It would mean that *something* or *somebody* is very selectably changing a bit here, another bit there, to increase a sample value here, decrease a sample value there, to cause the midrange level to rise or the treble level to decrease. And a cable is doing that? Really? That cable would need to possess more computing power than in the laptop I am typing this on.
The idea is just to ridiculous to seriously entertain.
Yet, you say, when I listen to these two transports and switch between one to the other, I am certain I do here a difference! And I am sure you would be honest and sincere. How can we reconcile this then?
The reason for this state of affairs lies in the way we perceive, in the way we process inputs from all our multiple sensors, remembered history and expectations, and from the mix come up with an opinion. It's not a kind story, but it has been confirmed for centuries really.
Not sure you want to hear more about it, but we can come back to it later.
If you are still in serious/learning/thinking mode, spend a few minutes looking up The McGurk effect, The ambulance color test, and read this:
https://www.harman.com/sites/default/files/white-paper/12/11/2015 - 05:54/files/AudioScience.pdf
forward to page 10, BLIND vs. SIGHTED TESTS – SEEING IS BELIEVING
If you are serious about this, I promise you a quantum leap in understanding! And for free 😉 (OK some time spend).
Jan
Well said Jan, not the first time many of us have pointed this out, only to fall on deaf ears (sorry Golden Ears🙂)
For many years I have been asking the people who chime on about bits not being bits to explain then what they are...
I am curious as after over 30 years of getting bits from one place to another I am curious as to what we have been missing in digital signal integrity... or in just getting the bits from a to b intact...
For many years I have been asking the people who chime on about bits not being bits to explain then what they are...
I am curious as after over 30 years of getting bits from one place to another I am curious as to what we have been missing in digital signal integrity... or in just getting the bits from a to b intact...
Neither is Harley.
The only jitter that matters is at the clock pin of the DAC chip. And generally, it is far, far lower than any hearing threshold, which is why jitter "demonstrations" have to be rigged in a very non-physical way.
Reading is a good thing; trying to learn about technology from a comic book isn't.
I sincerely hope you are wrong. In fact, I strongly suspect you are wrong. If you are right then it would be almost impossible to use an optical drive to load software onto a computer. I'm sure someone will correct me if I am wrong, but I seem to recall that data use of optical drives has weakish error correction because it can do retries, while audio and video use of optical drives has strong error correction because it cannot do retries. The net result is that both types of usage will almost always present bit-perfect data. That is all the drive is required to do, so we can assume that optical drives are perfect almost all of the time for all practical purposes. When imperfect, due to faults or media damage, it is usually very obvious.leadbelly said:
This is a very strange thread. It seems that some people think that personal opinions about matters of fact can be validated by seeking confirmation from a 'guru' - after first, presumably, carefully selecting the right 'guru'.
I am pleased to report that my personal opinion that optical drives are essentially perfect has been adequately confirmed by SY. As a chemist he knows about such things. Maybe tomorrow I will ask him to confirm that my personal opinion about Ohm's Law is correct.
Of course they wear out. To the point that they no longer play the disc, or do retries that sound like an old record getting stuck in a groove.
Not to worry. As long as they play, the bits are all right. ALL of the drives produce bit-perfect streams as matter of routine. The whole computer industry would collapse overnight if they didn't.
Jan
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While all good CD transports sound alike, not all CD transports are good. The industrial audio consultant Dick Pierce, noticed that over 15 years ago.
******************
>No, I've made these tests with at least 1/2 dozen DAC's. Digital cables
>aren't audible. They transmit data not analog waveforms.
Well, the problem is that you're both right and both wrong. Let
me give you a real-world example to illustrate the point.
Several years ago I was responsible for the software
implementation on a turn-key multi-track digital audio editing
workstation. We were introducing a new digital I/O module and
one of the requirements we set for ourselves was that it just
absolutely HAD to work with everyb coneivable piece of equipment
out there, even if that other equipment got its implementation
of the protocol wrong. If it couldn't talk, it should tell the
user exactly why it couldn't.
To that end, I begged, borrowed, stole, rented or leased every
piece of digital hardware I could get my hands on. This included
a wide mix of pro, semi-pro, consumer and high-end equipment.
In the process of testing, I connected a Tascam DA-30 DAT
recorder to a "highly regarded and favorably reviewed) high-end
DAC from a prestigious connecticut-based high-end company. with
certain cables, the residual noise floor on the output of the
DAC was simply AWFUL. Why?
The reason was simple: you had two utterly incompetent
implementations. The DA-30's SP/DIF output had miserable current
drive capability: load it up with enough capable capacitiance,
and the output went into slew-rate limiting and failed to meet
the rise-time requirement. The DAC, for all of it's thousands of
pretentious dollars, had the most MISERABLE design for clocking
around. The result was that, given the right cable with enough
capacitance, the resulting output had oodles of jitter in it.
Now, here's the ironic thing: the DAC used was considered by
many to be very "transparent" and was one of the few that, it
was said, COULD reveal differences in digital cables.
Well, that's NOT what was really happening. In reaility, it
idiot who designed the reclocking circuitry in the DAC simply
got it wrong in a seriously stupid fashion: the designer simply
made a DAC clock recovery circuit that was SO sensitive to small
changes in put conditions, that its performance was all over the
map.
Yet, members of the high-end press praised this piece of crap
for its "transparency. "It's obvious," it was said, "that
anything that DOES show such large differences in cables MUST be
transparent and high-resolution," when, in fact, precisely the
opposite was the case.
Far less price- and name-pretentious DACs, those with FAR better
clocking circuits did NOT exhibit this ridiculous sensitivity to
the cable: they were immune to the cariation that the more
expensive DAC simply could not handle properly.
So, if the problem exists, it's not because some of us are using
DACs that are immune to these errors, it's because some of you
AREN'T :-(.
The solution: boycott manufacturers that propogate these sorts
of pretentious but incompetent designs. And the high-end audio
business certainly has more than it's share.
| Dick Pierce |
| Professional Audio Development |
*****************************
https://groups.google.com/forum/?hl=en#!topic/rec.audio.high-end/uwb-KcM11gU
******************
>No, I've made these tests with at least 1/2 dozen DAC's. Digital cables
>aren't audible. They transmit data not analog waveforms.
Well, the problem is that you're both right and both wrong. Let
me give you a real-world example to illustrate the point.
Several years ago I was responsible for the software
implementation on a turn-key multi-track digital audio editing
workstation. We were introducing a new digital I/O module and
one of the requirements we set for ourselves was that it just
absolutely HAD to work with everyb coneivable piece of equipment
out there, even if that other equipment got its implementation
of the protocol wrong. If it couldn't talk, it should tell the
user exactly why it couldn't.
To that end, I begged, borrowed, stole, rented or leased every
piece of digital hardware I could get my hands on. This included
a wide mix of pro, semi-pro, consumer and high-end equipment.
In the process of testing, I connected a Tascam DA-30 DAT
recorder to a "highly regarded and favorably reviewed) high-end
DAC from a prestigious connecticut-based high-end company. with
certain cables, the residual noise floor on the output of the
DAC was simply AWFUL. Why?
The reason was simple: you had two utterly incompetent
implementations. The DA-30's SP/DIF output had miserable current
drive capability: load it up with enough capable capacitiance,
and the output went into slew-rate limiting and failed to meet
the rise-time requirement. The DAC, for all of it's thousands of
pretentious dollars, had the most MISERABLE design for clocking
around. The result was that, given the right cable with enough
capacitance, the resulting output had oodles of jitter in it.
Now, here's the ironic thing: the DAC used was considered by
many to be very "transparent" and was one of the few that, it
was said, COULD reveal differences in digital cables.
Well, that's NOT what was really happening. In reaility, it
idiot who designed the reclocking circuitry in the DAC simply
got it wrong in a seriously stupid fashion: the designer simply
made a DAC clock recovery circuit that was SO sensitive to small
changes in put conditions, that its performance was all over the
map.
Yet, members of the high-end press praised this piece of crap
for its "transparency. "It's obvious," it was said, "that
anything that DOES show such large differences in cables MUST be
transparent and high-resolution," when, in fact, precisely the
opposite was the case.
Far less price- and name-pretentious DACs, those with FAR better
clocking circuits did NOT exhibit this ridiculous sensitivity to
the cable: they were immune to the cariation that the more
expensive DAC simply could not handle properly.
So, if the problem exists, it's not because some of us are using
DACs that are immune to these errors, it's because some of you
AREN'T :-(.
The solution: boycott manufacturers that propogate these sorts
of pretentious but incompetent designs. And the high-end audio
business certainly has more than it's share.
| Dick Pierce |
| Professional Audio Development |
*****************************
https://groups.google.com/forum/?hl=en#!topic/rec.audio.high-end/uwb-KcM11gU
Speedskater,
It seems Jitter is more than likely the cause.
Maybe the reason I can hear the differences in transports is due to the DAC I am using. To me that still does not say the fault is strictly due to the DAC though, does it? I should also mention others have listened to the differences on my 2 channel system as well.
The DAC is a Cambridge Audio azur DAC Magic.
Digital coax cable, a 2 meter Tributaries Series 8 digital coax cable.
Have you read this white paper before by chance?
Is The AESEBU/SPDIF Interface Flawed
http://www.scalatech.co.uk/papers/dunn_hawksford_1992.pdf
.
It seems Jitter is more than likely the cause.
Maybe the reason I can hear the differences in transports is due to the DAC I am using. To me that still does not say the fault is strictly due to the DAC though, does it? I should also mention others have listened to the differences on my 2 channel system as well.
The DAC is a Cambridge Audio azur DAC Magic.
Digital coax cable, a 2 meter Tributaries Series 8 digital coax cable.
Have you read this white paper before by chance?
Is The AESEBU/SPDIF Interface Flawed
http://www.scalatech.co.uk/papers/dunn_hawksford_1992.pdf
.
1992 called and wants its boogyman back. See the green line? Below that is where you want to be. Oddly all competent DACs are. If you spend a lot you can get crappy performance
Attachments
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Yes, that must be it. It helps to not understand how digital audio works- this frees your mind to accept all sorts of bizarre fantasy.
You've assumed that the phenomenon is real. First demonstrate that it is before demanding explanations. If you understand how digital audio works, you'll know why the probability that you can actually hear an effect (assuming a system that isn't badly broken, so muting and skipping) is about equal to you demonstrating a perpetual motion machine.
I understand that you meant "naysayer" to be a pejorative, but sometimes the answer actually is "nay."
I understand that you meant "naysayer" to be a pejorative, but sometimes the answer actually is "nay."
Digital Audio is a trivial thing these days...
Digital transports are just spitting out a bit of digital data, I am confused how they can sound different and if its noise then lets see some figures and how this affects the downstream conversion... considering the performance of some PC sound cards (on that noisy PC motherboard) is excellent.
Digital transports are just spitting out a bit of digital data, I am confused how they can sound different and if its noise then lets see some figures and how this affects the downstream conversion... considering the performance of some PC sound cards (on that noisy PC motherboard) is excellent.
Your premise is "for any real sound difference, bits have to be changed" .
Is that premise true?
Simply no. You know what that means to your conclusions.
Why do you mention the McGurk effect?
If it is a a trick of sense that you can´t defeat, it doesn´t matter because cd-transports don´t speak.
Otoh if humans are able to learn which way not to be affected by the McGurk effect you should reexamine the way our perception works, because obviously people are able to counteract bias mechanisms. (all said wrt the underlying assumption that humans most likely are not perfect)
To illustrate the first possibility, remember our perception of virtual sound sources in the middle of the pair if both speaker produce the same signal.
As said before most people (there exists a minority that does only perceive two discrete sound source instead of the virtual one) perceive the virtual sound source and if you don´t change the two channel setup, no controlled listening test regime will be able to exclude this illusion.
Could you therefore conclude that no perception is real because this fundamental illusion exists? Of course you can´t.
If otoh it is a matter of training then the conclusions are obvious. 😉
Perhaps we can form this into a better direction? Your CD transport is, if made by most major manufacturers, and probably at 1/3 the price of the one you own) probably more than good enough to pass the data. Now, that means you can go spend your money and effort on DAC->downstream where you have a much much better chance of affecting things.
James, what we're trying to say is that the protocol to get data off a CD is extremely robust because it needs to be to ensure the data is reliably transported. The result of such errors would be dropouts or bloops/blips, which tend to be the case when either a CD is scratched beyond belief and/or in a car/discman (remember those?!) bouncing around, making the tracking hard.
So, at least to our level of interaction with the hardware, we can assume getting the data off the CD to be a solved problem. If there's a digital interconnect problem between your transport and your DAC, this will also manifest as bit loss/corruption and there come the pauses and blips/bloops. You would know about these, and it's time to replace hardware because something is broken. The noise/corruption immunity of digital is pretty amazingly good, which is why so much of what we take for granted just "works".
At the DAC, now, we can run into jitter/nonlinearities, and, as has been mentioned, there can be pathological input loading (don't do that), but that's much much more focused on the output side than it is on the receiving side.
James, what we're trying to say is that the protocol to get data off a CD is extremely robust because it needs to be to ensure the data is reliably transported. The result of such errors would be dropouts or bloops/blips, which tend to be the case when either a CD is scratched beyond belief and/or in a car/discman (remember those?!) bouncing around, making the tracking hard.
So, at least to our level of interaction with the hardware, we can assume getting the data off the CD to be a solved problem. If there's a digital interconnect problem between your transport and your DAC, this will also manifest as bit loss/corruption and there come the pauses and blips/bloops. You would know about these, and it's time to replace hardware because something is broken. The noise/corruption immunity of digital is pretty amazingly good, which is why so much of what we take for granted just "works".
At the DAC, now, we can run into jitter/nonlinearities, and, as has been mentioned, there can be pathological input loading (don't do that), but that's much much more focused on the output side than it is on the receiving side.
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