laurent.artaud[AT]free.fr" <"laurent.artaud[AT]free.fr wrote:
>> No.  There is no difference in the waveforms.  See my posts in
>> povray.binaries.misc.  Or download Adobe Audition demo version to
>> try out for yourself.
>
> Silly me! Of course there is no difference: the filters keep only the
> fundamental, which is a sin at 20KHz! It's a triangular waveform, not
> a sin waveform you have to use.
> ARGH!
> I'm starting to loose myself!
> I can't remember how the test was supposed to be done!
> Was it 20KHz or 22KHz? Was it a triangular or a square waveform?

Assuming you filter at 48kHz for a 96kHz sampling rate, a 20kHz square wave
will appear as a 20kHz sine wave because the next harmonic in a square wave
is at 3 times the fundamental.  Can't remember what it is for a triangle
wave though.  Will test out this evening listening to them to see if I can
tell any difference :-)

>> Please note that in [4] the scale goes from -32000 to 32000, so we
>> are seeing an error of between 1 and 2 per 32000, ie -84dB.
>> Theoretically there should be no error, but I had choose a quality
>> setting when I upsampled in stage 2, so I'm sure that effects the
>> result.
>
> Well, In my opinion, this error is just a rounding error during the
> conversions... It is not the one I was talking about.

Yes, I think it is rounding error too.

>> I can't hear the -84dB signal on my machine at work, I'll try it at
>> home but I'd imagine I would need to have my amplifier up *far*
>> higher than I do normally.
>>
>
> Well, if you can hear this signal, you have a really really really
> hi-end audio system. Most of the signal/noise ratios are around
> 70-80dB, so you might hear the amplifier's noise better that the
> signal.


claimed specs:

Frequency response: 10Hz - 80kHz -3dB
SNR: 98dB

Unfortunately I don't think my speakers can keep up with that! (claimed
40-22kHz -3dB)

One thing that I do notice is that if I turn my amp up to full while
connected to my 2496 soundcard I hear no hiss or noise at all.  Switch it to
my SoundBlaster Live and wham! there is so much hiss, even when all outputs
are muted in windows ;-)

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