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Seems it is

Posted by Jacques (A) on August 20, 2005 at 11:50:30

In Reply to: An electrical standard is not enough. posted by clarkjohnsen on August 19, 2005 at 08:17:57:

Sorry, Clark, but I have to disagree. You write:
> It doesn't transfer to tapes, LPs or CDs. For instance, does a stylus
> excursion to the outside denote a positive-going or a negative-going
> electrical signal? The AES is silent.
> Ditto with CDs.

(1) AS FOR LPs
**************
According to AES26-2001 paragraph 11.2 (for stereo LPs):
"An upward movement of the reproducing stylus, away from the recorded
surface, shall produce a positive output voltage at the terminal of
the cartridge designated as signal or positive (as opposed to return
or negative) terminal."

"Positive" being defined in paragraph 3.1 as:
"audio signal in any transmission medium (acoustical, mechanical,
electrical, magnetic, modulated carrier, and so on) that would
result from an increase (over the static atmospheric pressure)
of the instantaneous acoustic pressure on the diaphragm of a
pressure microphone, which causes displacement of the diaphragm
away from the sound entrance"

So, the answer to your question is clear: a stylus excursion to the
outside denotes a positive-going electrical signal, which represents
an increase of atmospheric pressure.

(2) AS FOR TAPES
****************
I read in paragraph 6.1:
"The direction of the magnetization of the tape corresponding to the presence
of an instantaneous positive audio signal shall be in the same direction
as that of the motion of the tape."
"The direction of the magnetization" (South-North) is as defined in
IEC 60094-1 (see paragraph 3.2)
BTW, the remaining of the paragraphs deals with FM recorded tapes, movies
tapes and other oddities

(3) AS FOR CDS
**************
as for CDs (and any other digital medium in this matter, I read in
paragraph 9.1 :
"For linearly represented digital audio data according to AES3,
positive analog voltages at the input of the analog to digital converter
(ADC) shall produce positive numbers at the output of the ADC"
"linearly represented digital audio data" applies to CD format.

You wrote:
> I tried to work with them on this at the time, but they refused
> to, ah, listen to me.
On paragraph 1, I read:
"The preservation of signal polarity in audio recording and processing
is important for two main reasons:
a) the polarity relationship between channels of a stereo pair or
multichannel set of signals is of fundamental importance in the
correct re-creation of the sound field;
b) some audio signals are sufficiently asymmetrical that polarity
inversion may be perceptually detected.
"
Seems to me that if they refused to listen to you, they did listen to
other people with the same concern.

You wrote:
"I tried to work with them on this at the time, but they refused
to, ah, listen to me.
Hence there are still no standards on Absolute Polarity."
I won't comment on the "hence", but I think there is a standard on Absolute
Polarity. Or maybe I'm plain wrong, but to help me change my mind,
just try to find out other arguments.
(for other inmates, no, I'm not bashing Clark, it's just the way things go
in any technical discussion when people disagree. Nothing personal!)

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Schiit Audio

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