Regarding +-32700 --
With a 16-bit sample size (as used by music CD's, etc.) you can
count up to 65,536 (including the starting zero). If you take
one bit to indicate whether the number is positive or negative,
that cuts the total counting range to 32,768 (or 32700 for
short).
So "plus" 32700 is the highest point on a waveform and "minus"
32700 is the lowest. In other words, in a graphic picture of an
audio wave, zero is the center line, and Full Scale is plus or
minus 32700.
If you drew a wave form (one cycle is all you need) that is just
a square shape with, say, 22 samples at plus 32700 and 22
samples at minus 32700, you'd have a harmonic-rich full-scale
signal at 1 kilohertz.
You get the +-32700 wave height by making sure the waveform
display is not zoomed in vertically, and then zooming in
*horizontally* until the individual sample "dots" are showing.
Then just drag the pencil tool at the top and bottom of the wave
display. Once you have one cycle, you can copy/paste it a few
times, then reselect them all and copy/paste again, and end up
with as much time duration of the 1kHz squarewave signal as you
like.
There are other issues involved in dealing with such a violent
signal in digital equipment, but this how you could make one
without special software.
To validate that a recorder is just cloning the input byte
stream, it probably doesn't matter much what the wave *shape*
is, so long as it goes full scale. I'm not sure about that, but
it seems reasonable that just about anything full scale would
get significantly messed with if it goes through another DA/AD
conversion. I would think that just 1 cycle, comprising a single
sample at plus full scale and the next sample at minus full
scale, would validate that an input is pure digital -- but I
haven't tested that.
ac
Allen Cobb
http://acobb.com
http://shakespeare.acobb.com
http://timbreproductions.com
-----Original Message-----
From:
Behalf Of Lou Judson
Sent: Wednesday, October 19, 2005 6:25 PM
To:
Subject: Re: [Nature Recordists] MT2496 digital input
Ah, very clear. That would indeed be a severe test for any
convertor!
I'll have to suggest it sometime on an audio elist I'm on.
Thanks for the details. But what does the +or-32700 mean? So
many
questions...
<L>
Lou Judson =95 Intuitive Audio
415-883-2689
On Oct 19, 2005, at 10:01 AM, Allen Cobb wrote:
> In most waveform editing programs (such as Sony SoundForge)
you
> can "draw" waveforms or drag individual samples to whatever
> level you want. In SoundForge, you can use the "insert
silence"
> command to create a short wave comprising only zero samples.
> Then with the "pencil tool" you can drag individual samples to
+
> or - 0db FS (that is, all the way up or all the way down).
Just
> don't play the result through your sound system unless the
level
> is set very low!
>
> ac
>
>
> Allen Cobb
>
> http://acobb.com
> http://shakespeare.acobb.com
> http://timbreproductions.com
>
>
> -----Original Message-----
> From:
> Behalf Of Lou
Judson
> Sent: Wednesday, October 19, 2005 11:01 AM
> To:
> Subject: Re: [Nature Recordists] MT2496 digital input
>
>
> Can you describe what you mean by this file? How do you make
it?
> Sorry
> if it is a dumb question...
>
> <L>
>
> Lou Judson =95 Intuitive Audio
> 415-883-2689
>
> On Oct 19, 2005, at 12:37 AM, Gianni Pavan wrote:
>
>> Create an "impossible" file with samples alternating
> among -max and
>> +max (-32700,+32700,-32700,+32700,....)
>> Play the file through a digital output
>
>
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> "Microphones are not ears,
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