"Pooh Bear" wrote in message
...
Clyde Slick wrote:

Its time to dredge out this old baby again!!

Here is a challenge for Graham:
A while ago Arnie got into a heated argument against John Atkinson
and Glenn Z regarding aspects of the J Test about whether or
not the signal should be dithered.
I would like you to revisit this issue and tell us whether
you think Arnie was correct, or if John and Glenn were correct.
Since you are on a similar level of technical expertise as
Glenn, I think your input into this matter
would be very helpful and interesting.
And a new discussion on the technical merits should
prove interesting, as well.

Here are some excerpts:

snipped for brevity

That's quite a meal you posted there Clyde. It raises a number of issues
that
were doubtless once contentional but now likely to be rather less of an
isssue due to technical improvements in conversion.

I had to print out what you posted but I was still unclear who exactly was
commenting on whom.

I'll reply thus - hopefully it'll answer your questions - at least in
part.


Use of dither.

Dither is essentially similar to adding noise to the signal to be
quantised.
I have heard undithered digital audio at low bit depth at Neve ( where the
possibilities existed to research such stuff ) and it truly sounds awful.
Like a buzz-saw almost.

Use of a careful amount of dither introduces *new samples* that 'smooth
out'
the reproduced waveform and provide a more acceptable result for human
listening.

That is a simpistic representation but essentially gives a workable
overview.

As to whether you should use a dithered signal to test a D-A depends on
which
characteristics you are seeking to measure. 'Horses for courses'.


Jitter.

The intelligent can deduce that jitter ( inaccuracy in the time domain )
can
be directly correlated as an equivalent error in the amplitude domain (
when
no attempt is made at jitter reduction ).

Early digital products sometimes experienced high levels of jitter. I was
involved in producing a report back in 1988 for the benefit of several
pro-audio manufacturers on this precise subject.

At worst, jitter can cause data recovery problems in the receiver of a
serial
digital signal ( e.g AES or SPDIF format ) that may cause signal muting.

My investigations indicated that one specific Japanese pro-audio
manufacturer
had a level of jitter that caused problems with much other digitally
interfaced equipment.

That specific Japanese manufacturer subsequently withdrew from the digital
pro-audio market.

Modern digital receivers have far 'cleverer' circuitry that can accomadate
jitter with more tolerance and reject it.

Does that help ?


It avoided the heart of the matter of contention, but anyway,
all that is between you, JA, Glenn Zelniker and Arnie.

no matter what happens with that one debate, sometime,
somehow you are going to have a big clash with Arnie.

that is because you are smarter than he is, you are more
highly educated than he is, more experienced than he is, and you
are actually a productive contributor in the world of product
developement in audio, which Arnie is not, at all. However,
Arnie perceives himself to be the brightest, most experienced and
most knowledgeable person posting her on RAO. So someday,
he is going to have to put you in your place. This is whetehr he
wants to or not, or tries to or not.

Arny has one advantage over you, though,.....He is insane,