Audio, hi-fi and car audio - Dirty Digital [sic.]

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Dirty Digital [sic.]

"Jim Lesurf"

Yes. I suspected he'd done that as a result of his persistent use of
undithered tones.

** Given that the only way to test a CD player's THD performance is by the
use of a special test signal CD - kindly tell us who makes & where one
can buy a test CD that contains sine wave tones that are stated to have been
deliberately digitally dithered ?

AFAIK none of the professional test CDs sold by Philips or Audio Technica
or anyone else incorporated dithering of the digitally generated 16 bit data
strems that constitute the sine wave test signals on the disk.

...... Phil

Dirty Digital [sic.]

In article , Phil Allison
wrote:

"Jim Lesurf"

Yes. I suspected he'd done that as a result of his persistent use of
undithered tones.

** Given that the only way to test a CD player's THD performance is by
the use of a special test signal CD

Which these days is easy enough to create for yourself if you know how to
generate dithered test waveforms and write them onto a CDR.

FWIW The example spectra on the webpages I wrote use the form of data which
I do use with a CD burner to create CDRs for audio replay. I created data
files of the type I'd normally write to CDR, and then used the data for the
FFTs.

Given how easy this is I doubt there'd be much commercial need these for a
conventional CD just to measure THD. Except perhaps for a tester/reviewer
who didn't know how to make the required test bands for themself.

AFAIK none of the professional test CDs sold by Philips or Audio
Technica or anyone else incorporated dithering of the digitally
generated 16 bit data strems that constitute the sine wave test signals
on the disk.

You'd have to specify which of the test bands in question are explicitly
intended for low-level THD measurements. Not dithering may be preferred for
non-THD measurement purposes. e.g. I would not dither an impulse waveform.
Nor would you have to for other special cases. Obvious examples being
44.1k/2 or 44.1k/4 sinusoids.

However if you look, for example, at the HFN II Test CD, that dithered some
bands for THD measurements. So such discs exist. Not seen a survey of other
discs. But since you ask I'll see if I can find out what disc is used for
the HFN tests that measure THD for CD as a function of signal level. They
show levels way below what NK claimed in his article.

You may be right, though, and NK is simply using a standard disc from
somewhere without dither, and without realising the implications of just
taking all the components except for the nominal frequency as 'distortion'.

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Dirty Digital [sic.]

"Eeyore" wrote in message
...

Failing that, a group of audio pros ought to picket the next edition of
HFN

Try and follow the thread you ******, it wasn't HFN but HFW.

Dirty Digital [sic.]

"Arny Krueger" wrote in message
...

I just thought I'd say Hi as the only other poster in this demented thread
who replies to any of your posts is that nutter Eeyore.
Do you think the others have you plonked?

Dirty Digital [sic.]

Sure, I heard that - but it is absolutely minute. There is absolutely no
way that could cause interference to audio equipment in a studio. To
find it I had to make a pickup, use all the gain my DAT had on its mic
input, then apply another 20dB later.

I stood exactly where the arrow pointed.

d

Sure this isn't caused by earth currents anywhere appearing on say the
mains incomer and another earth like perhaps one for the studio "tech"
earth?..

--
Tony Sayer

Dirty Digital [sic.]

tony sayer wrote:
Sure, I heard that - but it is absolutely minute. There is absolutely no
way that could cause interference to audio equipment in a studio. To
find it I had to make a pickup, use all the gain my DAT had on its mic
input, then apply another 20dB later.

I stood exactly where the arrow pointed.

d

Sure this isn't caused by earth currents anywhere appearing on say the
mains incomer and another earth like perhaps one for the studio "tech"
earth?..

That's quite possible.

d

Dirty Digital [sic.]

tony sayer wrote:

Sure, I heard that - but it is absolutely minute. There is absolutely no
way that could cause interference to audio equipment in a studio. To
find it I had to make a pickup, use all the gain my DAT had on its mic
input, then apply another 20dB later.

I stood exactly where the arrow pointed.

Sure this isn't caused by earth currents anywhere appearing on say the
mains incomer and another earth like perhaps one for the studio "tech"
earth?..

In the kilohertz region ?

Graham

Dirty Digital [sic.]

"Jim Lesurf"
Phil Allison

** Given that the only way to test a CD player's THD performance is by
the use of a special test signal CD

Which these days is easy enough to create for yourself if you know how to
generate dithered test waveforms and write them onto a CDR.

** That is a big "if" and got nothing to do with my Q.

(snip repeat of same silly opinion)

AFAIK none of the professional test CDs sold by Philips or Audio
Technica or anyone else incorporated dithering of the digitally
generated 16 bit data streams that constitute the sine wave test signals
on the disk.

You'd have to specify which of the test bands in question are explicitly
intended for low-level THD measurements.

** This is all nothing a bunch of circumlocution and irrelevant drivel .

Just like you bizarre excuses for publishing false info on the Quad ESL57

However if you look, for example, at the HFN II Test CD, that dithered
some
bands for THD measurements. So such discs exist.

** Huh ? Makes no sense at all.

You may be right, though, and NK is simply using a standard disc from
somewhere without dither, and without realising the implications of just
taking all the components except for the nominal frequency as
'distortion'.

** He would hardly be alone in that one.

Every CD player review I saw published in the 80s and through most of the
90s used such test tracks for THD evaluation - usually from one of the
Philips tests discs.

( While more modern so called " reviews " contain no objective tests and
only talk about the spurious imaginings of the demented audiophool doing the
review).

The " Denon Audio Technical CD " ( released in 1984 but still available,
AFAIK ) has a number of ( non dithered) 1001Hz sine wave tracks that are
stated to be for THD measurement, some with "emphasis" on and some with it
off, - all of them at 0 dB. The other 1001 Hz sine wave tracks at lower
levels ( ie -24 dB and -60 dB ) are stated to be for " dynamic range "
testing.

First generation CD player reviews published in ETI magazine circa 1983/4,
quoted THD figures for sine wave test levels down to -80 dB and INCLUDED
residual noise and spurious supersonic signals in the results.Then, the same
fictitious figures were used to create a graph of CD player " linearity " -
and otherwise good machines fared very badly.

...... Phil

Dirty Digital [sic.]

I noticed last night that one paragraph of the explanation on the page I
did wasn't what I'd intended, so I have altered the wording to make things
clearer. It is the para explaining why an undithered tone at 44.1k/5
generates components at its harmonics as a result of quantisation.

Slainte,

Jim

--
Change 'noise' to 'jcgl' if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Dirty Digital [sic.]