> Not sure what you mean by "it's not like it's a flat cut off after that". Any spectral content above 22.05 kHz is aliased to frequencies below 22.05 kHz -- th

> Not sure what you mean by "it's not like it's a flat cut off after that". Any spectral content above 22.05 kHz is aliased to frequencies below 22.05 kHz -- that is mathematically inescapable. Yes, that's what I mean. If you encode a 23kHz sound you don't get a flat signal as you'd get with a (-inf low pass filter) but an aliased one approximating the original; and as freq goes up, the errors introduced by aliasing (kind of) increase. You are also correct about mentioning the reconstruction filters and internal oversampling. In practice these errors don't matter, as we humans are, at the very best, barely able to hear anything up there (as in, is there a 23kHz sine vs is there nothing at all), let alone discern any difference between two different sounds (as in, is the sound emitted a 23kHz square or a 23kHz sine or a 23.5kHz sine), and even less when drowned by any signal in the human ear highly sensitive range. (Not even mentioning that getting into these areas start needing so much pressure to be perceived that it can become painful/damaging) So theory is all fun and games, because I guess ultimately my point is that in practice anything above 22kHz flat out doesn't matter. Admittedly I'm taking many many shortcuts and possible lies here and there, but I don't thing going "why doesn't Feynman fall through his chair" really helps. Let's all get out and enjoy some love and music already.