[Arny Krueger]

"Sean Conolly" wrote in message


I do understand that, but I'm discussing the perceived
effect, specifically in spatial perception. I'm not
disputing what you or Arny are saying, just that's it's
not really related to my line of thought - which was
speculating about how jitter could influence the stereo
image as some have claimed.

The most likely way that jitter could influence the stereo
image as some have claimed, is if they are imagining things.

When people are imagining things, one of their common refuges is the world
of "soundstaging". If you take "soundstaging" in its broadest reasonable
sense, its a truism. *Everyhing* effects soundstaging because soundstaging
can be a way of describing the totality of the results of sonic
reproduction.

In a technical discussion, reciting truisms that everybody knows and agrees
about is about the same as saying nothing.

But the real killer for my line of thought, as pointed
out by Arny, is that jitter should have the same effect
on both channels.

Hold that thought!

It can't be influencing the stereo
imaging unless it affects the channels differently.

Yes! Yes! Yes.

So now I can't imagine any way for jitter or lack of to have
the effects people have reported.

Hold that thought!

Their problem is that they were *hearing* jitter that was actually well
below the threshold of reliable perception. It was all imaginary, and the
vague terminology for describing what it supposedly sounded like should have
tipped us all off instantly. I have to admit it, I was in intellectual
bondage to the specter of digital jitter until I had a chance to do
side-by-side measurements of CD and LP playback. The difference is huge!!!

The true history of audio is that for almost a century, playing back audio
recordings included actual massive and audible amounts of FM distortion due
to mechanical wow, mechanical flutter, and scrape flutter. The LP was
particularly susceptible to FM distortion, as warped records are an endemic,
largely unsolved problem to this day.

Suddenly in came digital, and audible FM distortion became pretty much a
thing of the past. Strangely enough, after years of relative silence about
the audible FM distortion endemic in analog media, which science and
technology could never really banish completely, the problem dropped by
quite a few orders of magnitude.

This big lie progressed to the point where thousands of audiophiles actually
believed that jitter was a unique problem of digital, and that their LP
playback systems had no such difficulties. The truth was nearly the exact
opposite. Digital largely solved the problem of audible jitter, and analog
media particularly the LP, is loaded with it, to this day.

The high end audio pundits, responding to analog equipment advertiser demand
that something be done before the digital juggernaut totally eliminated
their business completely, started whining about jitter. Eventually, any
number of other hungry journalists, and technicians, hungry for something to
write about, jumped on the bandwagon.

One of the things I've been able to do is isolate a number of technical
tests of purportedly high end LP playback equipment. One common thread is
that they show *huge* amounts of jitter.

[Arny Krueger]

"Richard Crowley" wrote in message

"Sean Conolly" wrote ...
But the real killer for my line of thought, as pointed
out by Arny, is that jitter should have the same effect
on both channels. It can't be influencing the stereo
imaging unless it affects the channels differently. So
now I can't imagine any way for jitter or lack of to
have the effects people have reported.

People report all sorts of things that can't be measured
or explained scientifically.

The consumer high end audio business has raised this to what is certainly a
subcultural activity, and a pseudoscience, at best.

Whether you believe that the
perceptions are real and undefined, or psychological and
imagined depends on your philosophy.

It's really pretty simple - the means for verifying these reports is
well-known and generally not all that difficult to implement.

The question is not whether you believe in science, but rather whether your
belief in science is compartmentalized, or general.

[Randy Yates]

"Richard Crowley" writes:

"Sean Conolly" wrote ...
But the real killer for my line of thought, as pointed out by Arny, is
that jitter should have the same effect on both channels. It can't be
influencing the stereo imaging unless it affects the channels differently.
So now I can't imagine any way for jitter or lack of to have the effects
people have reported.

People report all sorts of things that can't be measured or explained
scientifically. Whether you believe that the perceptions are real and
undefined, or psychological and imagined depends on your philosophy.

When they can't reliably tell one source with the proported "thing" from
another without the "thing", I'd call that perception imagined.
--
% Randy Yates % "Though you ride on the wheels of tomorrow,
%% Fuquay-Varina, NC % you still wander the fields of your
%%% 919-577-9882 % sorrow."
%%%% % '21st Century Man', *Time*, ELO
http://www.digitalsignallabs.com

[Scott Dorsey]

Arny Krueger wrote:

One of the things I've been able to do is isolate a number of technical
tests of purportedly high end LP playback equipment. One common thread is
that they show *huge* amounts of jitter.

Yes, BUT they show huge amounts of jitter whose sidebands are now very
widely separated from the original signals. This is going to have a very
different sonic effect.

The question basically comes down to how much modulation is audible, AND
what modulation spectra are most audible.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Arny Krueger]

"Scott Dorsey" wrote in message

Arny Krueger wrote:

One of the things I've been able to do is isolate a
number of technical tests of purportedly high end LP
playback equipment. One common thread is that they show
*huge* amounts of jitter.

Yes, BUT they show huge amounts of jitter whose sidebands
are now very widely separated from the original signals.

???????????

The position of the sidebands for relatively small modulation indices (less
than 1%) is the same as the modulating frequency. Since most of the
modulating frequencies are due to mechanical effects, the frequencies are
relatively low.

Well, that's the theory.

I have my own results, and they are consistent with what follows, but for
grins I'll cite results by someone with the following vinyl setup:

The turntable is a Linn Sondek LP12 + all of the major upgrades up to and
including the Lingo power supply. It has not had the Cirkus or any
subsequent upgrades.

The pickup arm is a Linn Ittok LVII. This is a fairly early Ittok, with the
two-piece counterweight.

The cartridge is a Linn Karma AL22621.

The sidebands of a standard 3 KHz flutter test signal are at 2920 Hz and
2942 Hz.

So, the modulating frequency is 21 Hz.

The most common jitter frequencies will be related to things like the power
line (50 or 60 Hz) or framing frequencies (75 Hz for a CD). Their jitter
sidebands will therefore be 50, 60 or 75 Hz from the carrier.

The presumption that the sidebands will be more widely separated from the
original signals for a most digital audio components is not supported by the
relevant facts or actual measurements.

This is going to have a very different sonic effect.

The question basically comes down to how much modulation
is audible, AND what modulation spectra are most audible.

First we have to show that those sidebands are indeed further away from the
carrier, which runs counter to the relevant
facts.

Now, if you are talking scrape flutter, different story. ;-)