[Sean Conolly]

I've been poking around the net for information about word clock generators,
internal and external, rumored improvements, etc. One of the patterns I've
noticed is a lot of statements to the effect of "when I played back my
tracks I could hear a big improvement" - which strikes me as almost
irrelevant. It seems to me that improving playback is a minor benefit,
unless I plan on having everyone come over to my house to listen to my
tracks.

Yes I understand the importance of accurate playback during mixing so you
can make better decisions, but it seems to me that the speakers and the room
is going to blur the sound a lot more than clock jitter, at least in that
context. My concern is whether better clocking improves the tracks during
recording, and will this improvement be audible for other people?

What led me here was that I've been kicking around the idea of trying to get
some improvements out of my Motu 1296. It's done what I need well enough
that I'm more interested in getting it upgraded than replacing it outright -
recording is just one of my hobbies. I've heard that it has room for
improvement with the clock, and this is one of the mods that Black Lion
does. I was also interested in the idea of external word clock, but after
reading a long thread on this topic on Dan Lavry's PSW forum, I can see
where the benefits of this are dubious (reclocking from an external clock
shouldn't sound any better than the internal clock, and possibly worse). I
don't have any other gear to synch with, so I have no other reason to use an
external clock anyway.

I guess I don't have a specific question, I'm just curious what other think
on this topic.

Sean

[Mike Rivers]

Sean Conolly wrote:
I've been poking around the net for information about word clock generators,
internal and external, rumored improvements, etc. One of the patterns I've
noticed is a lot of statements to the effect of "when I played back my
tracks I could hear a big improvement"

This is usually an indication that the D/A converter isn't very good. A
good converter won't be improved by an external clock. But if the
playback really does sound better, don't knock it.

It seems to me that improving playback is a minor benefit,
unless I plan on having everyone come over to my house to listen to my
tracks.

In that respect, yes, but it might help you to mix better if you can
hear more accurately.

My concern is whether better clocking improves the tracks during
recording, and will this improvement be audible for other people?

Again, if it does, it means that it's improving a converter that isn't
very good. Chances are a better converter would be better overall than a
converter that was poor enough to be improved by an external clock.

What led me here was that I've been kicking around the idea of trying to get
some improvements out of my Motu 1296.
I've heard that it has room for
improvement with the clock, and this is one of the mods that Black Lion
does.

I don't know what he does, but it's likely he replaces the A/D converter
chip with something that has a better phase locked loop than the
original, or if it's based on parts rather than a chip, rebuilds the
PLL. I suspect that whatever he does improves its performance with the
internal clock, which most likely makes the improvement, if any, with an
external clock, negligible.

I was also interested in the idea of external word clock, but after
reading a long thread on this topic on Dan Lavry's PSW forum, I can see
where the benefits of this are dubious

The benefit of an external clock, and indeed what makes one necessary,
is to synchronize clocks within a system. That's its primary purpose,
not to make a badly clocked converter sound better.

I guess I don't have a specific question, I'm just curious what other think
on this topic.

P'tooey!

--
If you e-mail me and it bounces, use your secret decoder ring and reach
me he
double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
)

[Neil Gould]

Mike Rivers wrote:
Sean Conolly wrote:
I've been poking around the net for information about word clock
generators, internal and external, rumored improvements, etc. One of
the patterns I've noticed is a lot of statements to the effect of
"when I played back my tracks I could hear a big improvement"

This is usually an indication that the D/A converter isn't very good.
A good converter won't be improved by an external clock. But if the
playback really does sound better, don't knock it.

Word clock is invaluable in systems that synchronize multiple external
interfaces or where tracking may involve a bi-directional flow between
recorders or external effects. But I'm hard pressed to come up with any
reason why the sound would audibly differ in a "one way" system with a
single interface. The worst that one might discover in a laboratory is that
a poorly designed internal clock, PLL, etc. might deliver samples with
timing that spreads a bit, but it would probably be next to impossible to
detect such a thing aurally unless the timing is so bad that it is basically
broken.

--
Neil

[Ethan Winer]

"Neil Gould" wrote:

I'm hard pressed to come up with any reason why the sound would audibly
differ in a "one way" system with a single interface.

I'm sure this is the correct answer. Jitter is irrelevant and inaudible in
modern gear. I'm not convinced it was ever a problem, even at the dawn of
affordable digital in the 1980s. Even a 50-cent crystal oscillator is highly
stable. I'm certain that when people believe they hear an improvement from
changing clocks it is entirely in their mind, or due to comb filtering, and
is exactly the same as improvement audiophiles claim to hear when they
change speaker cables etc.

As Sean said, "speakers and the room is going to blur the sound a lot more
than clock jitter." No kidding. Room reflections and their "timing errors"
are literally 1,000 times larger and stronger than anything possible from
clock jitter. Much more he

http://www.ethanwiner.com/audibility.html
http://www.ethanwiner.com/believe.html
http://www.ethanwiner.com/dither.html
http://www.ethanwiner.com/audiophoolery.html

--Ethan

[Richard Crowley]

"Ethan Winer" wrote ...
I'm sure this is the correct answer. Jitter is irrelevant and inaudible in
modern gear. I'm not convinced it was ever a problem, even at the dawn of
affordable digital in the 1980s. Even a 50-cent crystal oscillator is
highly
stable. I'm certain that when people believe they hear an improvement from
changing clocks it is entirely in their mind, or due to comb filtering,
and is exactly the same as improvement audiophiles claim to hear when they
change speaker cables etc.

And caused by exactly the same effect -- namely hucksters trying
to peddle "up-market" goods to technically illeterate customers.
If you can convince someone that a $20 cable will fix the "jitter
problem" caused by a $5 cable, you can make an easy $15.

[Scott Dorsey]

Ethan Winer ethanw at ethanwiner dot com wrote:
I'm sure this is the correct answer. Jitter is irrelevant and inaudible in
modern gear. I'm not convinced it was ever a problem, even at the dawn of
affordable digital in the 1980s. Even a 50-cent crystal oscillator is highly
stable. I'm certain that when people believe they hear an improvement from
changing clocks it is entirely in their mind, or due to comb filtering, and
is exactly the same as improvement audiophiles claim to hear when they
change speaker cables etc.

A 50-cent crystal oscillator is highly stable, but it's also only
free-running. There are a lot of pieces of equipment out there that
use derived clocks generated by PLL oscillators that are locked to the
clock of the incoming datastream.

You can argue that this is not competent design practice today in an
age where buffering is cheap, but it still goes on a lot.

As Sean said, "speakers and the room is going to blur the sound a lot more
than clock jitter." No kidding. Room reflections and their "timing errors"
are literally 1,000 times larger and stronger than anything possible from
clock jitter. Much more he

That doesn't mean that having a good clock isn't important. BUT, it is only
important at the converters themselves. If the converter is free-running
it's probably stable... if it has to lock to something else, make sure you
have a good quality piece of equipment.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mike Rivers]

Ethan Winer wrote:

I'm sure this is the correct answer. Jitter is irrelevant and inaudible in
modern gear. I'm not convinced it was ever a problem, even at the dawn of
affordable digital in the 1980s. Even a 50-cent crystal oscillator is
highly stable.

There's a little more to it than frequency stability. That's easy.
Getting modulation out of the clock is a little harder. The PLL does its
best to deal with the crappiest clocks, but it does so by making some
assumptions about what it has to filter out.

It turns out that if you know the characteristics of the PLL in a given
converter, and you're a good enough designer to be able to control the
noise spectrum of the clock, you may be able to improve on a particular
converter with an external clock. What this means is Clock Generator A
might make Converter A sound better (because Company A designed both of
them and they're good designers), but not Converter B or C, but maybe
Converter D because it's similar enough to Converter A.

Honestly, I don't believe the "I hooked up the Westclox and just started
playing some old tracks, and my grandmother ran in from another room
asking what I did because it sounds so much better." stories, but I
believe that a clever designer can improve a particular converter with
an external clock if he knows enough about the characteristics of the
converter's PLL and he knows how to design for it.

Of course a better speaker or a better broadband trap can make more
difference than a new clock, so when it comes to bang-for-buck, this is
not the way to improve your sound (unless you need it for system
synchronization - in which case you should be prepared for a possible
minor degradation). But if you already have the best speakers you can
afford, you might get a bit of an improvement (or not) with a new clock
in the system.

Here's a white paper on the subject of external clocks, toned down for
the general public - no math, but based on too much research:
http://www.drawmer.com/uploads/File/...clock-sync.pdf




--
If you e-mail me and it bounces, use your secret decoder ring and reach
me he
double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
)

[Sean Conolly]

"Mike Rivers" wrote in message
...
Sean Conolly wrote:

What led me here was that I've been kicking around the idea of trying to
get some improvements out of my Motu 1296. I've heard that it has room
for improvement with the clock, and this is one of the mods that Black
Lion does.

I don't know what he does, but it's likely he replaces the A/D converter
chip with something that has a better phase locked loop than the original,
or if it's based on parts rather than a chip, rebuilds the PLL. I suspect
that whatever he does improves its performance with the internal clock,
which most likely makes the improvement, if any, with an external clock,
negligible.


I was doing some tests today with my Motu, and I rediscovered that I have to
use the clock on the PCI card, or I get these weird glitches - every fourth
sample will hold the same value for a few cycles. Picture the output as if
it was a four sample circular buffer, and then stop updating one of the
buffer slots so it just hold the same value for 10-20 cycles. When I switch
the master to the the PCI card it runs perfectly, but if I can't use the
1296 as the master then I'm not sure if I'm going to get any benefit from
modding that clock.

And in the process of really listening and looking critically at what the
Motu produces - I realized it's probably the best piece of gear in my little
office here. The only thing I might need is to pick up a 421 card as a
replacement or spare for the 321 card.

Sean

[Sean Conolly]

"Scott Dorsey" wrote in message
...
Ethan Winer ethanw at ethanwiner dot com wrote:
I'm sure this is the correct answer. Jitter is irrelevant and inaudible in
modern gear. I'm not convinced it was ever a problem, even at the dawn of
affordable digital in the 1980s. Even a 50-cent crystal oscillator is
highly
stable. I'm certain that when people believe they hear an improvement from
changing clocks it is entirely in their mind, or due to comb filtering,
and
is exactly the same as improvement audiophiles claim to hear when they
change speaker cables etc.

A 50-cent crystal oscillator is highly stable, but it's also only
free-running. There are a lot of pieces of equipment out there that
use derived clocks generated by PLL oscillators that are locked to the
clock of the incoming datastream.

You can argue that this is not competent design practice today in an
age where buffering is cheap, but it still goes on a lot.

I'd expect that practice is intended to keep the converter running at the
same pace as the source, more than just syncing samples. Today I compared my
two A/D boxes and found that the little E-Mu is slower than the Motu by a
millisecond per minute - in a D/A converter that kind difference would
eventually overflow the buffer if the clock wasn't sync'ed to the incoming
data.


That doesn't mean that having a good clock isn't important. BUT, it is
only
important at the converters themselves. If the converter is free-running
it's probably stable... if it has to lock to something else, make sure you
have a good quality piece of equipment.

Isn't also true that in a multi-channel converter, the internal clock is a
separate circuit driving all the converters? A single converter with a clock
on the chip is fine, but when there's more than one in the same box an
internal master clock is needed.

Sean

[Mike Rivers]

Sean Conolly wrote:

I was doing some tests today with my Motu, and I rediscovered that I have to
use the clock on the PCI card, or I get these weird glitches - every fourth
sample will hold the same value for a few cycles.

If this is MOTU-speak for "I have to use its internal clock. I get
glitches when using the external clock" this suggests that it's not
really synchronizing to the external clock. Is there an indicator,
either an LED on the front panel or something on the MOTU software
control panel that indicates PLL lock?

There's no published standard for the voltage level of word clock signal
level (either as output level or input sensitivity), only the rise time
of the waveform. I've encountered hardware pairs (a source and
destination) that aren't compatible. When connected, the clock source
doesn't have enough poop to reliably trigger the sync input. I first
encountered this when trying to synchronize a Mackie hard disk recorder
and digital console. With the console's word clock output properly
terminated at the HDR end, the clock voltage dropped below the input
threshold of the HDR and the HDR's "sync" light would blink
intermittently. Swap the word clock master/slave relationship and the
console would lock up solidly to the HDR's clock output. It was possible
to make the HDR work with the console's word clock output by turning off
the termination (there's a switch) on the HDR but that's not the ideal
situation.

This is one of those problems that you just have to analyze. Without
having exactly the same setup that you have, it's impossible for anyone
to make the right guess.



--
If you e-mail me and it bounces, use your secret decoder ring and reach
me he
double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
)

[Scott Dorsey]

In article ,
Sean Conolly wrote:
"Scott Dorsey" wrote in message
...
Ethan Winer ethanw at ethanwiner dot com wrote:
I'm sure this is the correct answer. Jitter is irrelevant and inaudible in
modern gear. I'm not convinced it was ever a problem, even at the dawn of
affordable digital in the 1980s. Even a 50-cent crystal oscillator is
highly
stable. I'm certain that when people believe they hear an improvement from
changing clocks it is entirely in their mind, or due to comb filtering,
and
is exactly the same as improvement audiophiles claim to hear when they
change speaker cables etc.

A 50-cent crystal oscillator is highly stable, but it's also only
free-running. There are a lot of pieces of equipment out there that
use derived clocks generated by PLL oscillators that are locked to the
clock of the incoming datastream.

You can argue that this is not competent design practice today in an
age where buffering is cheap, but it still goes on a lot.

I'd expect that practice is intended to keep the converter running at the
same pace as the source, more than just syncing samples. Today I compared my
two A/D boxes and found that the little E-Mu is slower than the Motu by a
millisecond per minute - in a D/A converter that kind difference would
eventually overflow the buffer if the clock wasn't sync'ed to the incoming
data.

Right. So you have an internal clock that is synched to the source clock
so they all run at the same rate overall.

Imagine having four 2-channel A/D boxes feeding an 8-channel recorder, for
instance. They all need to lock off some master clock because otherwise
they wouldn't be sending data at quite the same rate. Normally that master
clock is in the recorder.

That doesn't mean that having a good clock isn't important. BUT, it is
only
important at the converters themselves. If the converter is free-running
it's probably stable... if it has to lock to something else, make sure you
have a good quality piece of equipment.

Isn't also true that in a multi-channel converter, the internal clock is a
separate circuit driving all the converters? A single converter with a clock
on the chip is fine, but when there's more than one in the same box an
internal master clock is needed.

Actually, even on two-channel converters, there is an internal clock which
is usually not on the same chip as the converters. Sometimes it's actually
built into the S-PDIF receiver chip.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Ethan Winer]

Scott,

There are a lot of pieces of equipment out there that use derived clocks
generated by PLL oscillators that are locked to the clock of the incoming
datastream.

Yes, and I was addressing only a single clock as used in a sound card.

--Ethan

[Ethan Winer]

Mike,

Honestly, I don't believe the "I hooked up the Westclox and just started
playing some old tracks, and my grandmother ran in from another room
asking what I did because it sounds so much better." stories

Exactly, and that's all I'm addressing, which in turn is what Sean (OP) was
asking about.

Here's a white paper on the subject of external clocks

In that paper I see exactly what I object to:

"People have installed an external word clock and have reported an apparent
sonic improvement, generally described as more open and less harsh."

Jitter manifests as FM sidebands some number of dB below the music. Typical
values I see are -110 to -140 dB, with is WAY below the noise of 16-bit
digital, which in turn is WAY below the room noise of 16+ tracks mixed
together. Even one microphone in a quiet room capturing an acoustic guitar
will have ambient noise well above the noise floor of 16 bits.

I'm just trying to keep this stuff in perspective. :-)

--Ethan

[Mike Rivers]

On Nov 3, 10:29 am, "Ethan Winer" ethanw at ethanwiner dot com
wrote:

Jitter manifests as FM sidebands some number of dB below the music. Typical
values I see are -110 to -140 dB

Is that with an external clock source? Remember, when you connect two
boxes, and defect in one (like a ground problem or a noisy power
supply) can be imposed on the other.

If there are sidebands 60 Hz removed from a given frequency, that
probably won't hurt anything. It might even make a bass part sound
better. But if they're 2-3 kHz removed, they can get in the way of
some pretty useful stuff.

Now don't get me wrong. I'm not a strong advocate of using an external
clock unless you need one. But I can understand the principle that
predicts the problem, even though the magnitude of the problem may be
tiny in some circumstances. I've not heard any problems even when I
run my Mackie HDR24/96 using a 45+ year old Wavetek function generator
as the word clock source when I need to change the speed/pitch of a
track, but I wouldn't be surprised if some golden ears would tarnish
at the thought, if not the sound.

Remember, too, that the better the converter's clock design, the more
immune it is to effects of external noise.

[Ethan Winer]

Mike,

Is that with an external clock source?

I dunno, it's from tables in Ken Pohlmann's book Principles of Digital Audio
and a few other places.

If there are sidebands 60 Hz removed from a given frequency, that probably
won't hurt anything. It might even make a bass part sound better. But if
they're 2-3 kHz removed, they can get in the way of some pretty useful
stuff.

Yes, but only if the side-bands are audible. If they're 100+ dB below the
music, they're not audible no matter how golden one's ears are.

Now don't get me wrong. I'm not a strong advocate of using an external
clock unless you need one. But I can understand the principle that
predicts the problem, even though the magnitude of the problem may be tiny
in some circumstances.

Actually, one of the famous designers (Dan Lavry?) argues strongly the
opposite, that an external clock can only make jitter worse. The explanation
involves math that's over my head, but I believe him. However, all that
stuff is still just mental masturbation because it's always 100+ dB down and
thus irrelevant.

I've not heard any problems even when I run my Mackie HDR24/96 using a 45+
year old Wavetek function generator as the word clock source when I need
to change the speed/pitch

I rest my case. :-)

--Ethan

[Mark]

I've not heard any problems even when I run my Mackie HDR24/96 using a 45+
year old Wavetek function generator as the word clock source when I need
to change the speed/pitch

I rest my case. :-)

--Ethan

and the effects of jitter are EASILY detected on a spectrum analyzer
looking at simple test tones...

anyone who thinks they hear a change of one clock configurartion vs
another can easily verify what they think they hear with a spectrum
analyzer.

If you are using a function generator as a clock source, as a test you
can apply intentional FM of various deviations and frequencies to the
clock and create HUGH amounts of jitter to see how much it really
takes to become audible.

Mark

[Mike Rivers]

Ethan Winer wrote:

Actually, one of the famous designers (Dan Lavry?) argues strongly the
opposite, that an external clock can only make jitter worse. The
explanation involves math that's over my head, but I believe him.
However, all that stuff is still just mental masturbation because it's
always 100+ dB down and thus irrelevant.

His explanation is correct in the "all things as expected" case.
However, there can be things wrong (we're not just talking bad designs
here, though bad design or implementation is a factor) where sidebands
resulting from jitter can be much greater than -100 dB. And then there's
the issue of putting them in places where they won't do a lot of harm.

One of the things that Lavry is very careful about is not just low
jitter clocking, but clock circuits that are immune to being buggered by
outside influences such as external clock generators, power supply hum,
stray EMI, and ground loops. The clock might be find by itself, and then
the real world comes along and screws things up. That's where theory and
practice are not the same, which, in theory, they should be. g

--
If you e-mail me and it bounces, use your secret decoder ring and reach
me he
double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
)

[Randy Yates]

"Ethan Winer" ethanw at ethanwiner dot com writes:
[...]
Actually, one of the famous designers (Dan Lavry?) argues strongly the
opposite, that an external clock can only make jitter worse. The
explanation involves math that's over my head, but I believe
him.

Hi Ethan,

Do you have a reference?
--
% Randy Yates % "She's sweet on Wagner-I think she'd die for Beethoven.
%% Fuquay-Varina, NC % She love the way Puccini lays down a tune, and
%%% 919-577-9882 % Verdi's always creepin' from her room."
%%%% % "Rockaria", *A New World Record*, ELO
http://www.digitalsignallabs.com

[Les Cargill]

Randy Yates wrote:
"Ethan Winer" ethanw at ethanwiner dot com writes:
[...]
Actually, one of the famous designers (Dan Lavry?) argues strongly the
opposite, that an external clock can only make jitter worse. The
explanation involves math that's over my head, but I believe
him.

Hi Ethan,

Do you have a reference?

I'm not Ethan, but....

http://www.lavryengineering.com/white_papers/jitter.pdf

Briefly, jitter is based on error in absolute time. As the time
goes down, the effect of a change on a unit circle at a higher
Fs goes up - a 1 nanosecond hit causes twice as much error at
2Fs than at 1Fs.

Jitter also has a different spectrum at twice the clock rate.

--
Les Cargill

[Randy Yates]

Les Cargill writes:

Randy Yates wrote:
"Ethan Winer" ethanw at ethanwiner dot com writes:
[...]
Actually, one of the famous designers (Dan Lavry?) argues strongly the
opposite, that an external clock can only make jitter worse. The
explanation involves math that's over my head, but I believe
him.

Hi Ethan,

Do you have a reference?

I'm not Ethan, but....

http://www.lavryengineering.com/white_papers/jitter.pdf

Thanks Les. Ethan, is this the paper you were referring to?
--
% Randy Yates % "How's life on earth?
%% Fuquay-Varina, NC % ... What is it worth?"
%%% 919-577-9882 % 'Mission (A World Record)',
%%%% % *A New World Record*, ELO
http://www.digitalsignallabs.com

[Sean Conolly]

"Mike Rivers" wrote in message
news
Sean Conolly wrote:

I was doing some tests today with my Motu, and I rediscovered that I have
to use the clock on the PCI card, or I get these weird glitches - every
fourth sample will hold the same value for a few cycles.

If this is MOTU-speak for "I have to use its internal clock. I get
glitches when using the external clock" this suggests that it's not really
synchronizing to the external clock. Is there an indicator, either an LED
on the front panel or something on the MOTU software control panel that
indicates PLL lock?

I have three basic choices: using the 1296 box as the master, using the PCI
card as the master, or using the external clock input on the 1296. I'm
assuming that using the 1296 as the master would be the better choice since
it's part of the same hardware as the converters, but in practice it turns
out that I have to use the PCI card to avoid the glitches I described. It
may be that the card clock should take priority since it's doing the actual
recording to disk, or maybe there's little too much spread between the
internal clocks of the card and the box, or that the box is better at
sync'ing to an external clock (external to the box) than the card is.

There's no obvious indicator - it does flash the chosen sample rate for a
while and stop, but the pattern is the same using either the box or the card
as the master. I've never seen the display flash during recording, but I
don't watch it that much after I get my levels set. Not a big deal to me,
other than every couple of years I forget why I had the master set to the
card and go through the discovery process again.

Sean

[Sean Conolly]

"Mark" wrote in message
...


I've not heard any problems even when I run my Mackie HDR24/96 using a
45+
year old Wavetek function generator as the word clock source when I
need
to change the speed/pitch

I rest my case. :-)

--Ethan

and the effects of jitter are EASILY detected on a spectrum analyzer
looking at simple test tones...

anyone who thinks they hear a change of one clock configurartion vs
another can easily verify what they think they hear with a spectrum
analyzer.

If you are using a function generator as a clock source, as a test you
can apply intentional FM of various deviations and frequencies to the
clock and create HUGH amounts of jitter to see how much it really
takes to become audible.

I think that the effects of clock jitter are going to be in the time domain
much more than the frequency domain. The most common benefit that people
report with improved word clocks is tighter stereo imaging, which of course
is how the listener's brain interprets the signals from each ear into a
spatial point. It can be easily shown that the position of a source can be
moved in the stereo field just by manipulating the timing, so I can
understand how the accuracy of the timing errors could influence where the
source sits in the field. It also seems that the nature of the jitter is a
factor: if it's a slow modulation it should be imperceptible, and the same
if it's random - at least in relation to audio frequencies.

Just as a guess, I'll speculate that jitter would have to be in the 100
microsecond range to perceptually effect the imaging, and even then only if
the average is modulating at something near audible frequencies. If it's
jumping around too much the brain will ignore it, and if it's drifting
slowly enough then you're not conscious of it, at least until someone points
it out. Obviously if it's a constant offset then that would just change
where the source sits in the field, not the size of it.

Again this is just my guess: the brain is a strange organic DSP and may be
far more sensitive than I'm imagining here. The very fact that we perceive a
sound coming from multiple speakers as a single point says a lot about how
adaptive our hearing is.

Sean

[Mike Rivers]

Sean Conolly wrote:

I have three basic choices: using the 1296 box as the master, using the PCI
card as the master, or using the external clock input on the 1296. I'm
assuming that using the 1296 as the master would be the better choice since
it's part of the same hardware as the converters

That's a good starting point, but . . you have to do what works in the
system.

but in practice it turns
out that I have to use the PCI card to avoid the glitches I described. It
may be that the card clock should take priority since it's doing the actual
recording to disk, or maybe there's little too much spread between the
internal clocks of the card and the box, or that the box is better at
sync'ing to an external clock (external to the box) than the card is.

I suspect the latter. But if you want to pursue it, look at the driver
situation. Are you up to date? And more important, is the manufacturer
up to date? And are all your terminations and non-terminations correct?
I'll bet the card's word clock input has a fixed termination, and what
you're feeding it with may not develop enough voltage across that load
to properly synchronize the card's clock input. My Lynx L22's software
control panel has a set of indicators including one labeled "Lock"
that's red if it doesn't have a good clock signal from whatever source
you've selected.



--
If you e-mail me and it bounces, use your secret decoder ring and reach
me he
double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
)

[Arny Krueger]

"Sean Conolly" wrote in message


I think that the effects of clock jitter are going to be
in the time domain much more than the frequency domain.

Ask anybody whose taken any EE courses in the last 50 years. The time domain
and the frequency domain are very closely related. It's darn hard to do
something in one domain without doing some analogous thing(s) in the other.
Remember, F = 1/T where F is frequency and T is time. Relationships don't
get much simpler than that!

The most common benefit that people report with improved
word clocks is tighter stereo imaging, which of course is
how the listener's brain interprets the signals from each
ear into a spatial point.

That may be intuitive to you, but it doesn't hold up in reality.

What FM distortion (jitter's technical name) does at modest levels is add
sidebands around every tone in the recorded sound. These tones are
aharmonic, so if they are loud enough, they are going to make the music
sound kind of sour.

At higher levels, jitter simply keeps digital receivers from ever locking
into the input signal. If the jitter level is inconsistent, you may have
clicks and pops as the digital receiver falls in and out of lock.

At really high levels, jitter keeps the digital receiver from ever locking
into the signal, and you have silence.

The reason why I can say these things so boldly is that one day maybe 5-7
years ago I built a device that added jitter to a digital audio signal in
ways and amounts that I could control from mild to wild. I then tried out a
bunch of digital audio gear with different amounts and kinds of jitter, and
carefully listened to it and also measured its effects on the equipment.

One of the devices I had that did very little to correct jitter was a fairly
pricey (in its day) Denon DAC. Another device that did wonders with a
jittery input signal was essentially a cheap Technics surround receiver.

It can be easily shown that the
position of a source can be moved in the stereo field
just by manipulating the timing,

Yes, but that requires timing changes on the order of tens of milliseconds
and even fractions of a second. Jitter at its worst involves changes on the
order of nanoseconds or picoseconds. So, jitter involves changes that are
on the order of a thousandth or a millionth of what it takes to cause image
shifting.

so I can understand how
the accuracy of the timing errors could influence where
the source sits in the field. It also seems that the
nature of the jitter is a factor: if it's a slow
modulation it should be imperceptible, and the same if
it's random - at least in relation to audio frequencies.

Jitter is usually imperceptible because at this time, it is pretty trivial
and inexpensive to make equipment that simply reduces it to such low levels
that the next trick is to accurately measure it, let alone actually hear it.
That's one of the nice things about digital, a good DAC can make horrendous
amounts of jitter simply and effectively disappear.

An example of a piece of audio gear that has a DAC that makes huge amounts
of jitter disappear might be a $150 surround receiver.

Just as a guess, I'll speculate that jitter would have to
be in the 100 microsecond range to perceptually effect
the imaging, and even then only if the average is
modulating at something near audible frequencies.

Think 10-100 times larger. That much jitter takes a major screw-up to
actually have. Not to say that people just plugging cables and flicking
switches in a studio haven't done this to themselves at one time or the
other.

If it's
jumping around too much the brain will ignore it, and if
it's drifting slowly enough then you're not conscious of
it, at least until someone points it out.

Low frequency FM distortion is like flutter and more even more likely wow.
Play a good piano recording with audible amounts of flutter and/or wow, and
nobody needs to tell you that is there. The ear is very sensitive to low
frequency FM distortion, and its sensitivity to it goes down as the jitter
frequency goes up.

Obviously if
it's a constant offset then that would just change where
the source sits in the field, not the size of it.

No, a constant amount of FM distortion is called a pitch change. If you
want to change the imaging you *have* to do different things to each of the
channels that you are listening to. Since most jitter gets tacked onto a
digital signal that is also multichannel (degenerate case: Stereo) all the
embedded channels get the same bad treatment. bottom line, no image shift.

Again this is just my guess:

I'm sure you mean well, but unfortunately you've got just about everything
wrong. I'll bet money that you've been reading lots of subjective comments
about jitter. Since there are a lot of pro audio ragazines that employ some
writers are actually no more savvy than your average consumer high end audio
ragazine, a lot of really weird stuff shows up where it shouldn't.

the brain is a strange
organic DSP and may be far more sensitive than I'm
imagining here.

Actually, what the brain does with sound and music is pretty well
understood. Music, Your Brain, and Ecstasy by Jourdain would be a good
starter, and then for the heavy lifting there are the writings of Zwicker
and Fastl.

[Arny Krueger]

"Ethan Winer" ethanw at ethanwiner dot com wrote in
message

Mike,

Is that with an external clock source?

I dunno, it's from tables in Ken Pohlmann's book
Principles of Digital Audio and a few other places.

If there are sidebands 60 Hz removed from a given
frequency, that probably won't hurt anything. It might
even make a bass part sound better. But if they're 2-3
kHz removed, they can get in the way of some pretty
useful stuff.

Agreed, but for more details, please see the post to another subthead that I
just posted.

60 Hz (and 120 Hz) are good frequencies to use when talking about jitter
because they are very common in the real world.

One less-obvious that this happens is when a digital signal gets mixed with
a lot of hum. Obviously, you can't hear the hum directly. And, a
well-designed digital input will filter low frequencies out. But there is
gear that is not well-designed. ;-(

At any rate, some place along the way, most digital signals pass through
some kind of a level-sensitive logic device like a Schmidt Trigger. The hum
makes the trigger points shift back and forth at the frequencies contained
in the hum which of course are generally power-line related. Bang! Jitter.

BTW, this is the general approach I used to make a jitter-inducing device.

Yes, but only if the side-bands are audible. If they're
100+ dB below the music, they're not audible no matter
how golden one's ears are.

Agreed.

Now don't get me wrong. I'm not a strong advocate of
using an external clock unless you need one. But I can
understand the principle that predicts the problem, even
though the magnitude of the problem may be tiny in some
circumstances.

Actually, one of the famous designers (Dan Lavry?) argues
strongly the opposite, that an external clock can only
make jitter worse.

I suspect that most of that is because its external. It suffers the slings
and arrows of equipment grounding, and bad cabling, and the like. External
DACs for CD players were always a disaster waiting to happen. Put as much as
you can inside a box and engineer the box carefully (Dan's your guy, there!)
and all is well.

The explanation involves math that's
over my head, but I believe him. However, all that stuff
is still just mental masturbation because it's always
100+ dB down and thus irrelevant.

Exactly. Jitter often stops being a problem when it is *only* 80 dB down,
but 100 dB is both readily doable and gives you lots of insurance. I think
that 120 dB down is not all that rare. One of the cheap surround receivers I
tested put any jitter in a signal that it could lock on, about 115 dB down.
;-)

I've not heard any problems even when I run my Mackie
HDR24/96 using a 45+ year old Wavetek function generator
as the word clock source when I need to change the
speed/pitch

Been there, done that.

I rest my case. :-)

As is usual, exactly right. ;-)

Back to things that actually matter like room acoustics!

[Mark]

Again this is just my guess: the brain is a strange organic DSP and may be
far more sensitive than I'm imagining here. The very fact that we perceive a
sound coming from multiple speakers as a single point says a lot about how
adaptive our hearing is.




I say again..

use a spectrum analyzer!!

You can SEE jitter well below the level anyone can hear it.

There is no guesswork needed..

Mark

[Ethan Winer]

Sean,

The most common benefit that people report with improved word clocks is
tighter stereo imaging

Yes, I know that's the common report, but I think the reports are just wrong
and those people would never identify low jitter from high jitter in a blind
test. This article I linked to earlier explains my best guess as to why
people report changes in "imaging" and clarity etc when changing clocks, or
speaker cables, or other things that are unlikely to make an audible change:

http://www.ethanwiner.com/believe.html

The very fact that we perceive a sound coming from multiple speakers as a
single point says a lot about how adaptive our hearing is.

It's actually much simpler than that. If a sound is directly in front of
you, it has the same volume and arrival time at both ears. So whether the
sound really is in front of you, or arrives from two separate loudspeakers,
both ears receive the same signal. So it's not any mystique in the ears or
brain, but simple physics and acoustics.

--Ethan

[Ethan Winer]

Do you have a reference?

I know I've seen it several times at Gearslutz, both by the author (pretty
sure it's Dan Lavry) and by other people referring to him saying that. Maybe
go to Gearslutz.com and search for posts by Dan. As I recall he posts under
his own name there.

--Ethan

[Ethan Winer]

Thanks Les. Ethan, is this the paper you were referring to?

I've mostly seen him explain it in forum posts.

--Ethan

[Ethan Winer]

One of the cheap surround receivers I tested put any jitter in a signal
that it could lock on, about 115 dB down.

Yep. A total non-issue.

Back to things that actually matter like room acoustics!

LOL - okay then!

--Ethan

[Sean Conolly]

"Arny Krueger" wrote in message
...
"Sean Conolly" wrote in message


I think that the effects of clock jitter are going to be
in the time domain much more than the frequency domain.

Ask anybody whose taken any EE courses in the last 50 years. The time
domain and the frequency domain are very closely related. It's darn hard
to do something in one domain without doing some analogous thing(s) in the
other. Remember, F = 1/T where F is frequency and T is time. Relationships
don't get much simpler than that!

The most common benefit that people report with improved
word clocks is tighter stereo imaging, which of course is
how the listener's brain interprets the signals from each
ear into a spatial point.

That may be intuitive to you, but it doesn't hold up in reality.

What FM distortion (jitter's technical name) does at modest levels is add
sidebands around every tone in the recorded sound. These tones are
aharmonic, so if they are loud enough, they are going to make the music
sound kind of sour.

At higher levels, jitter simply keeps digital receivers from ever locking
into the input signal. If the jitter level is inconsistent, you may have
clicks and pops as the digital receiver falls in and out of lock.

At really high levels, jitter keeps the digital receiver from ever locking
into the signal, and you have silence.

The reason why I can say these things so boldly is that one day maybe 5-7
years ago I built a device that added jitter to a digital audio signal in
ways and amounts that I could control from mild to wild. I then tried out
a bunch of digital audio gear with different amounts and kinds of jitter,
and carefully listened to it and also measured its effects on the
equipment.

One of the devices I had that did very little to correct jitter was a
fairly pricey (in its day) Denon DAC. Another device that did wonders with
a jittery input signal was essentially a cheap Technics surround receiver.

It can be easily shown that the
position of a source can be moved in the stereo field
just by manipulating the timing,

Yes, but that requires timing changes on the order of tens of milliseconds
and even fractions of a second. Jitter at its worst involves changes on
the order of nanoseconds or picoseconds. So, jitter involves changes that
are on the order of a thousandth or a millionth of what it takes to cause
image shifting.

so I can understand how
the accuracy of the timing errors could influence where
the source sits in the field. It also seems that the
nature of the jitter is a factor: if it's a slow
modulation it should be imperceptible, and the same if
it's random - at least in relation to audio frequencies.

Jitter is usually imperceptible because at this time, it is pretty trivial
and inexpensive to make equipment that simply reduces it to such low
levels that the next trick is to accurately measure it, let alone actually
hear it. That's one of the nice things about digital, a good DAC can make
horrendous amounts of jitter simply and effectively disappear.

An example of a piece of audio gear that has a DAC that makes huge amounts
of jitter disappear might be a $150 surround receiver.

Just as a guess, I'll speculate that jitter would have to
be in the 100 microsecond range to perceptually effect
the imaging, and even then only if the average is
modulating at something near audible frequencies.

Think 10-100 times larger. That much jitter takes a major screw-up to
actually have. Not to say that people just plugging cables and flicking
switches in a studio haven't done this to themselves at one time or the
other.

If it's
jumping around too much the brain will ignore it, and if
it's drifting slowly enough then you're not conscious of
it, at least until someone points it out.

Low frequency FM distortion is like flutter and more even more likely wow.
Play a good piano recording with audible amounts of flutter and/or wow,
and nobody needs to tell you that is there. The ear is very sensitive to
low frequency FM distortion, and its sensitivity to it goes down as the
jitter frequency goes up.

Obviously if
it's a constant offset then that would just change where
the source sits in the field, not the size of it.

No, a constant amount of FM distortion is called a pitch change. If you
want to change the imaging you *have* to do different things to each of
the channels that you are listening to. Since most jitter gets tacked onto
a digital signal that is also multichannel (degenerate case: Stereo) all
the embedded channels get the same bad treatment. bottom line, no image
shift.

Again this is just my guess:

I'm sure you mean well, but unfortunately you've got just about everything
wrong. I'll bet money that you've been reading lots of subjective comments
about jitter. Since there are a lot of pro audio ragazines that employ
some writers are actually no more savvy than your average consumer high
end audio ragazine, a lot of really weird stuff shows up where it
shouldn't.

the brain is a strange
organic DSP and may be far more sensitive than I'm
imagining here.

Actually, what the brain does with sound and music is pretty well
understood. Music, Your Brain, and Ecstasy by Jourdain would be a good
starter, and then for the heavy lifting there are the writings of Zwicker
and Fastl.

I'm going to politely disagree on most of your points, probably because I
didn't I meandered around instead of making a plain statement:
The brain isn't like a piece of hardware, we interpret imaging mostly by the
time difference in when the event reaches each ear, and that our ears are
far more sensitive to this than to sideband frequencies buried in the
signal. That's my personal assertion - I can offer nothing to back it up and
may well be dead wrong.

I also disagree that aural perception is well understood, especially in
regards to timing. Well studied yes, but not understood. If aural perception
were an exact science we wouldn't need listening tests for gear, would we?

Sean

[Arny Krueger]

"Sean Conolly" wrote in message


"Arny Krueger" wrote in message
...

"Sean Conolly" wrote in message


I think that the effects of clock jitter are going to be
in the time domain much more than the frequency domain.

Ask anybody whose taken any EE courses in the last 50
years. The time domain and the frequency domain are very
closely related. It's darn hard to do something in one
domain without doing some analogous thing(s) in the
other. Remember, F = 1/T where F is frequency and T is
time. Relationships don't get much simpler than that!

The most common benefit that people report with improved
word clocks is tighter stereo imaging, which of course
is how the listener's brain interprets the signals from
each ear into a spatial point.

That may be intuitive to you, but it doesn't hold up in
reality.

What FM distortion (jitter's technical name) does at
modest levels is add sidebands around every tone in the
recorded sound. These tones are aharmonic, so if they
are loud enough, they are going to make the music sound
kind of sour.

BTW, I find it very interesting that so much has been written about the
alleged sound of jitter, but so few have come up with anything that
resembles this characterizations what jitter sounds like. If one actually
ever hears audible amounts of jitter, it literally jumps out at you.

At higher levels, jitter simply keeps digital receivers
from ever locking into the input signal. If the jitter
level is inconsistent, you may have clicks and pops as
the digital receiver falls in and out of lock.

At really high levels, jitter keeps the digital receiver
from ever locking into the signal, and you have silence.

The reason why I can say these things so boldly is that
one day maybe 5-7 years ago I built a device that added
jitter to a digital audio signal in ways and amounts
that I could control from mild to wild. I then tried out
a bunch of digital audio gear with different amounts and
kinds of jitter, and carefully listened to it and also
measured its effects on the equipment.

One of the devices I had that did very little to correct
jitter was a fairly pricey (in its day) Denon DAC.
Another device that did wonders with a jittery input
signal was essentially a cheap Technics surround
receiver.

It can be easily shown that the
position of a source can be moved in the stereo field
just by manipulating the timing,

Yes, but that requires timing changes on the order of
tens of milliseconds and even fractions of a second. Jitter at its worst
involves changes on the order of
nanoseconds or picoseconds. So, jitter involves changes
that are on the order of a thousandth or a millionth of
what it takes to cause image shifting.

so I can understand how
the accuracy of the timing errors could influence where
the source sits in the field. It also seems that the
nature of the jitter is a factor: if it's a slow
modulation it should be imperceptible, and the same if
it's random - at least in relation to audio frequencies.

Jitter is usually imperceptible because at this time, it
is pretty trivial and inexpensive to make equipment that
simply reduces it to such low levels that the next trick
is to accurately measure it, let alone actually hear it.
That's one of the nice things about digital, a good DAC
can make horrendous amounts of jitter simply and
effectively disappear.

An example of a piece of audio gear that has a DAC that
makes huge amounts of jitter disappear might be a $150
surround receiver.

Just as a guess, I'll speculate that jitter would have
to be in the 100 microsecond range to perceptually
effect the imaging, and even then only if the average is
modulating at something near audible frequencies.

Think 10-100 times larger. That much jitter takes a
major screw-up to actually have. Not to say that people
just plugging cables and flicking switches in a studio
haven't done this to themselves at one time or the other.

If it's
jumping around too much the brain will ignore it, and if
it's drifting slowly enough then you're not conscious of
it, at least until someone points it out.

Low frequency FM distortion is like flutter and more
even more likely wow. Play a good piano recording with
audible amounts of flutter and/or wow, and nobody needs
to tell you that is there. The ear is very sensitive
to low frequency FM distortion, and its sensitivity to
it goes down as the jitter frequency goes up.

Obviously if
it's a constant offset then that would just change where
the source sits in the field, not the size of it.

No, a constant amount of FM distortion is called a pitch
change. If you want to change the imaging you *have* to
do different things to each of the channels that you are
listening to. Since most jitter gets tacked onto a
digital signal that is also multichannel (degenerate
case: Stereo) all the embedded channels get the same bad
treatment. bottom line, no image shift.

Interesting that so many are so far out in left field when it comes to
characterizing the subjective effect of a steady-state clock frequency
error. It is really where music 101 hits digital technology 101. Simple
stuff over which there is actually no controversy at all among knowlegable
people.

Again this is just my guess:

I'm sure you mean well, but unfortunately you've got
just about everything wrong. I'll bet money that you've
been reading lots of subjective comments about jitter.
Since there are a lot of pro audio ragazines that
employ some writers are actually no more savvy than your
average consumer high end audio ragazine, a lot of
really weird stuff shows up where it shouldn't.

the brain is a strange
organic DSP and may be far more sensitive than I'm
imagining here.

Actually, what the brain does with sound and music is
pretty well understood. Music, Your Brain, and Ecstasy
by Jourdain would be a good starter, and then for the
heavy lifting there are the writings of Zwicker and
Fastl.

Note that our correspondent regrettably instnatly this well-known and
generally-accepted knowlege base competely out of hand

I'm going to politely disagree on most of your points,

Your gun, your bullet, your foot.

Well studied yes, but not understood. If aural perception
were an exact science we wouldn't need listening tests for gear, would we?

Let's cut to the chase. You can disagree with most of my techical points,
but you do so at your own risk. Most of the ideas you put foreward, one of
which was more erroneious than the next, were developed by people who knew
little about digital technology, and did only casual listening tests. That's
easy for me to say, because almost *nobody* bites the bullet like say Ethan
and I, and puts any of these wild assertions to a reliable test.

Audio is both Art and Science and one ignores either one at considerable
risk to their own personal development.

[Ethan Winer]

almost *nobody* bites the bullet like say Ethan and I

Yep, you can identify the pioneers by the arrows in their backs.

[Mark]

I'm going to politely disagree on most of your points, probably because I
didn't I meandered around instead of making a plain statement:
The brain isn't like a piece of hardware, we interpret imaging mostly by the
time difference in when the event reaches each ear, and that our ears are
far more sensitive to this than to sideband frequencies buried in the
signal. That's my personal assertion - I can offer nothing to back it up and
may well be dead wrong.

I also disagree that aural perception is well understood, especially in
regards to timing. Well studied yes, but not understood. If aural perception
were an exact science we wouldn't need listening tests for gear, would we?

Sean- Hide quoted text -

- Show quoted text -

Sean,

the fact that you fail to realize is that the "time distortions" that
you are concerned about are mathematically tied to the "sidebands in
the frequency domain". If you phase or frequency modulate a signal
(what you call time distortion) it WILL create sidebands in the
frequency domain that a spectrum anlyzer is perfectly capable of
displaying.

So while you may consider it an indirect observation, any modulation
in the phase/ time domain WILL also create sidebands that can be seen
on a spectrum analyzer. Therefore one of the best ways of looking for
phase/frequency distortion is to look in the frequency domain. This
has nothing to do with human hearing, it has everything to do with
modulation theory. The time doman and frequency domain are related.

Mark

[Arny Krueger]

"Ethan Winer" ethanw at ethanwiner dot com wrote in
message

almost *nobody* bites the bullet like say Ethan and I

Yep, you can identify the pioneers by the arrows in their
backs.

The good news is that there are now places like this, where proper reliable
listening tests are *The Standard*:

http://www.hydrogenaudio.org/

The other kind of news is that while the true pioneering work in reliable
listening tests was done ca. 1975, some 33 years later, so many people are
still wandering in the dark.

[Mike Rivers]

Arny Krueger wrote:

BTW, I find it very interesting that so much has been written about the
alleged sound of jitter, but so few have come up with anything that
resembles this characterizations what jitter sounds like. If one actually
ever hears audible amounts of jitter, it literally jumps out at you.

I suspect that this is because jitter, other than in the extreme,
doesn't really hear a sound. You don't hear a stray tone or an increase
in distortion. What you perceive is the effect of jitter on what you're
hearing. This is where the "shrinking sound field" description comes
from, I think, though I can offer no psychoacoustic or electronic reason
for it to be so.



--
If you e-mail me and it bounces, use your secret decoder ring and reach
me he
double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
)

[Ethan Winer]

Mike,

This is where the "shrinking sound field" description comes from, I think,
though I can offer no psychoacoustic or electronic reason for it to be so.

Right, I don't buy it either. As soon as someone says some tweak or other
affected the sound stage or fullness, I'm sure it's comb filtering in their
listening room. Comb filtering is proven to exist in huge amounts even in
treated rooms, so that's the most sensible explanation. I'm sure Occam will
agree. :-)

--Ethan

[Sean Conolly]

"Mark" wrote in message
...


I'm going to politely disagree on most of your points, probably because I
didn't I meandered around instead of making a plain statement:
The brain isn't like a piece of hardware, we interpret imaging mostly by
the
time difference in when the event reaches each ear, and that our ears are
far more sensitive to this than to sideband frequencies buried in the
signal. That's my personal assertion - I can offer nothing to back it up
and
may well be dead wrong.

I also disagree that aural perception is well understood, especially in
regards to timing. Well studied yes, but not understood. If aural
perception
were an exact science we wouldn't need listening tests for gear, would
we?

Sean- Hide quoted text -

- Show quoted text -

Sean,

the fact that you fail to realize is that the "time distortions" that
you are concerned about are mathematically tied to the "sidebands in
the frequency domain". If you phase or frequency modulate a signal
(what you call time distortion)

Sorry - I'm just not being clear with what I'm thinking, and I can't seem to
find the right way to describe it.


So while you may consider it an indirect observation, any modulation
in the phase/ time domain WILL also create sidebands that can be seen
on a spectrum analyzer. Therefore one of the best ways of looking for
phase/frequency distortion is to look in the frequency domain. This
has nothing to do with human hearing, it has everything to do with
modulation theory. The time doman and frequency domain are related.


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.

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.

Sean

[Richard Crowley]

"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.

[Scott Dorsey]

Richard Crowley wrote:
"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.

Sometimes I believe one, sometimes I believe another.

The thing about stereo imaging is that all kinds of tonal changes can
change perceived imaging. Add low order even harmonic distortion and
folks will hear it as the image fuzzing out. Increase the top end and
people perceive it as the image getting tighter, on top of the tonal
difference. It's all happening in your brain.
--scott




--
"C'est un Nagra. C'est suisse, et tres, tres precis."