Archived from groups: rec.audio.high-end (More info?)
Stewart Pinkerton <patent3@dircon.co.uk> wrote in message
news:<Kc5Gc.24114$MB3.7322@attbi_s04>...
> On Sun, 04 Jul 2004 07:39:58 GMT, Stereophile_Editor@compuserve.com
> (John Atkinson) wrote:
>> if you doubt the articles in Stereophile, I suggest you read Barry
>> Blesser's compendium on digital audio in the October 1978 issue of
>> the Journal of the Audio Engineering Society, where the problems of
>> word-clock jitter were first described in an audio context (to the
>> best of my knowledge). A Stereophile article showing how different
>> analog signals can be reconstructed from identical bitstreams can
>> be found at http
/www.stereophile.com/reference/1290jitter. This,
>> too, is based on an AES paper, this time by Stephen Harris, and a
>> third article can be found at
>> http/www.stereophile.com/reference/590jitter. A fourth article,
>> showing measured differences, goes up in the stereophile.com
>> archives on Monday.
>
> Hardly new knowledge. Jitter has been acknowledged as a problem in
> digital audio since the '60s - telecomms being several decades
> ahead of so-called 'high end' audio, as usual.
With respect Stewart, I think you are being a tad disingenuous here.
Yes, the problems of jitter were known in telecommunications work.
But it was only with the advent of practical digital audio in the
1970s, with the pioneering work of the BBC in the UK, Sony, NHK and
Denon in Japan, and 3M and the late Dr. Thomas Stockham at Soundstream
in the US, that digital theory became applicable to audio. Far from
the Blesser paper that I mentioned being "decades" behind, it was
published in 1978, just a handful of years after the first digital
audio devices were prototyped. Bob Stuart's work on jitter reduction
in Meridian players followed the Blesser paper by a decade, but that
was still just 5 years after the commercial launch of the CD medium.
>> You may think it unlikely, Mr. Seufert, but that doesn't mean it
>> doesn't exist. The problem is that there is no clock in the disc
>> data.
>
> Exactly! In a standalone player, the only clock is the free-running
> DAC clock, which also controls the data-reading servo. Hence, *if*
> that clock has vanishingly low phase noise, and *if* the power
> supplies are absolutely clean, there can be no jitter in the output
> signal, other than that of the A/D converter used to make the
> original digital master.
I really don't think we disagree, Stewart. I would say that my position
is that your word "if" conceals a multitude of design sins on the part
of product designers, sins that, according to the measurements
published in Stereophile and other review magazines, allow time-base
errors to propagate through to the recovered analog signal. I agree
with you that such design sins are poor engineering; I would merely
point out to you and Mr. Mr. Seufert that because something in theory
can be made to be perfect, that doesn't mean all real-world solutions
are also perfect.
<snip>
>> Around 12 years ago, this subject was examined by Ed Meitner and
>> Bob Gendron in an AES paper. To their surprise, they found -- and I
>> duplicated their work -- that riding on the DC power rail supplying
>> the ICs in a DAC was the audio signal described by the data that was
>> being processed. If you think about it, this is astonishing.
>
> It's not really astonishing, but it *is* a sign of poor system design.
I agree Stewart, But it is also not uncommon in cost-compromised
players with inadequate power supplies. Again, practical implementation
of theoretically perfect circuit topologies can leave a lot to be desired.
> See any current Meridian player for a fine example of how it should
> be done - or just hook up any old transport to a Benchmark DAC-1.
Yup. The Benchmark is an extraordinary product. Its designer, BTW,
claims that it will pass EEC RF emission standards with its cover
removed, which, if true, is a testament to the layout of its pcb.
> It's unfortunate that your august publication still makes the fatal
> error of assuming that a DAC which actually *is* sensitive to
> different transports is somehow 'superior', when the plain *fact*
> is that it's basically broken.
I am not sure that Stereophile has said this, at least not since the
early 1990s (if then). When you say "still makes" this error, Stewart,
are you aware of a recent instance?
John Atkinson
Editor, Stereophile
Stewart Pinkerton <patent3@dircon.co.uk> wrote in message
news:<Kc5Gc.24114$MB3.7322@attbi_s04>...
> On Sun, 04 Jul 2004 07:39:58 GMT, Stereophile_Editor@compuserve.com
> (John Atkinson) wrote:
>> if you doubt the articles in Stereophile, I suggest you read Barry
>> Blesser's compendium on digital audio in the October 1978 issue of
>> the Journal of the Audio Engineering Society, where the problems of
>> word-clock jitter were first described in an audio context (to the
>> best of my knowledge). A Stereophile article showing how different
>> analog signals can be reconstructed from identical bitstreams can
>> be found at http
/www.stereophile.com/reference/1290jitter. This,>> too, is based on an AES paper, this time by Stephen Harris, and a
>> third article can be found at
>> http
/www.stereophile.com/reference/590jitter. A fourth article,>> showing measured differences, goes up in the stereophile.com
>> archives on Monday.
>
> Hardly new knowledge. Jitter has been acknowledged as a problem in
> digital audio since the '60s - telecomms being several decades
> ahead of so-called 'high end' audio, as usual.
With respect Stewart, I think you are being a tad disingenuous here.
Yes, the problems of jitter were known in telecommunications work.
But it was only with the advent of practical digital audio in the
1970s, with the pioneering work of the BBC in the UK, Sony, NHK and
Denon in Japan, and 3M and the late Dr. Thomas Stockham at Soundstream
in the US, that digital theory became applicable to audio. Far from
the Blesser paper that I mentioned being "decades" behind, it was
published in 1978, just a handful of years after the first digital
audio devices were prototyped. Bob Stuart's work on jitter reduction
in Meridian players followed the Blesser paper by a decade, but that
was still just 5 years after the commercial launch of the CD medium.
>> You may think it unlikely, Mr. Seufert, but that doesn't mean it
>> doesn't exist. The problem is that there is no clock in the disc
>> data.
>
> Exactly! In a standalone player, the only clock is the free-running
> DAC clock, which also controls the data-reading servo. Hence, *if*
> that clock has vanishingly low phase noise, and *if* the power
> supplies are absolutely clean, there can be no jitter in the output
> signal, other than that of the A/D converter used to make the
> original digital master.
I really don't think we disagree, Stewart. I would say that my position
is that your word "if" conceals a multitude of design sins on the part
of product designers, sins that, according to the measurements
published in Stereophile and other review magazines, allow time-base
errors to propagate through to the recovered analog signal. I agree
with you that such design sins are poor engineering; I would merely
point out to you and Mr. Mr. Seufert that because something in theory
can be made to be perfect, that doesn't mean all real-world solutions
are also perfect.
<snip>
>> Around 12 years ago, this subject was examined by Ed Meitner and
>> Bob Gendron in an AES paper. To their surprise, they found -- and I
>> duplicated their work -- that riding on the DC power rail supplying
>> the ICs in a DAC was the audio signal described by the data that was
>> being processed. If you think about it, this is astonishing.
>
> It's not really astonishing, but it *is* a sign of poor system design.
I agree Stewart, But it is also not uncommon in cost-compromised
players with inadequate power supplies. Again, practical implementation
of theoretically perfect circuit topologies can leave a lot to be desired.
> See any current Meridian player for a fine example of how it should
> be done - or just hook up any old transport to a Benchmark DAC-1.
Yup. The Benchmark is an extraordinary product. Its designer, BTW,
claims that it will pass EEC RF emission standards with its cover
removed, which, if true, is a testament to the layout of its pcb.
> It's unfortunate that your august publication still makes the fatal
> error of assuming that a DAC which actually *is* sensitive to
> different transports is somehow 'superior', when the plain *fact*
> is that it's basically broken.
I am not sure that Stereophile has said this, at least not since the
early 1990s (if then). When you say "still makes" this error, Stewart,
are you aware of a recent instance?
John Atkinson
Editor, Stereophile
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