Re: [ARSCLIST] Sampling Theory (was Fred Layn's post on the Studer list re: Quantegy)

[Eric Jacobs <ericj@xxxxxxxxxxxxxxxxxxx>]

For kicks, I just ran the Cardas Test record, Tracks 2b and 2c, 1 to 30 kHz
sweep, and was effectively flat at 30 kHz.  The second harmonic at 60 kHz
was still clearly visible at about -30 dB, with the noise floor at -60 dB.
The response wasn't perfectly flat throughout the sweep, but the point is
that good analog gear (vinyl or magnetic tape) is perfectly capable of
reproducing a usable signal well beyond 20 kHz.

Digitizing and playing back a sine wave is easy.  Try a square wave and
see what happens.  Try a 10 kHz square wave sampled at 44.1 kHz - you
will find that the DAC will return a 10 kHz sine wave, not the original
square wave.  It starts getting close at 192 kHz - the square wave starts
looking more square with a good DAC.  What does sample rate mean to
impulses and other non-sinusoidal waveforms as produced by brass,
percussion and vocals?

The above comments in no way speak to what people can hear or not hear,
nor does it make an argument that higher sample rates are always better.
It does make the point that the ADC-DAC chain is not yet a perfect
reproduction of the original analog signal.  Whether what is lost in the
ADC-DAC translation is audible is something that many of us are still
trying to assess.

Eric Jacobs
The Audio Archive


-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx]On Behalf Of Dave Bradley
Sent: Monday, January 17, 2005 12:04 PM
To: ARSCLIST@xxxxxxxxxxxx
Subject: Re: [ARSCLIST] Sampling Theory (was Fred Layn's post on the
Studer list re: Quantegy)


I find it interesting that people point to subjective studies about what
can be sensed above 20 KHz, or above 15 KHz for that matter, and say that
because digital doesn't go there it's inferior. Take note that the
cartridge on your turntable isn't going there either, and with good reason,
the vinyl that the stylus is being dragged through can't reproduce up there
either. There may be harmonics up there, but analog isn't delivering it. So
if the problem is that digital isn't giving you something which you can't
hear, but can sense, keep in mind that analog isn't giving that to you
either.

The fact of the matter is that a pure sinewave, when digitized properly,
and then played back through a proper DAC will give you that same pure
sinewave again. It doesn't give you stepped response. It doesn't give you a
triangle or square wave. It gives you that pure sinewave.  Just because
zooming in on the waveform in your favorite DAW software shows you
individual sample values and a less than smooth wave form doesn't mean that
the playback will be that way.  Keep in mind that in the end, what you are
hearing is analog generated from a set of digital instructions or
samples.  You are still hearing analog.