Some years ago, some newsgroup readers made
a big fuss that there was a low pass filter on the
Apple IIGS. The IIGS has a low pass filter at 26kHz
frequencies. What those people kept arguing was
that this halved the sampling rate compared to CD.
This is total nonsense. The maximum frequency
that can be accurately captured by a given rate of
sampling is half the sampling rate. This is denoted
by the Nyquist theorem.
Fact is, practically all digital audio equipment has
low pass filters. CD players have them and PC
sound cards have them.
Take a look at Tom's Hardware's review of the new
Audigy2 card from Creative. It specifically points
out a low pass filter.
I'm just thinking how funny it was that people were
blaming Apple for putting in the filter when in fact
there's nothing to blame. Without such a filter all
you get is extra noise above 1/2 the sample rate.
I even recall that someone came out with a IIGS
emulator and promoted it saying that it lacked the
low pass filter. Shouldn't the Mac's audio out
have one too? It probably does.