"Keith Williams" wrote in message
T...
In article ,
lid says...
snip
Except for one thing...when they played the CD back
unfiltered, people would find their tweeters melting
for some weird reason....44.1kHz! at huge powers!
BS. Were it unfiltered aliasing would make the CD sound terrible.
The filter has to be in there for any sampled system. They didn't
"all of a sudden" figure out that they needed a filter.
Aliasing happens on the analog to digital conversion, not the digital to
analog conversion. That's why low-pass filters are put 'in front' of analog
to digital converters.
When going from digital to analog, all you *really* need is a sample/hold
circuit to maintain output until the next digital sample comes through for
conversion. But the step change from one sample to the next, if done with a
very fast slew rate can introduce some harmonics (rapid step changes are
always rich in high harmonics). But this is *not* aliasing ala Nyquist.
These can be 'smoothed' with a variety of filter circuits.
daestrom