This is something I've wondered for a long long while, but never spent the time to research. The typical digital flow is the analog sound comes into a microphone, into an analog lowpass filter, then an A/D which digitizes it. On playback out of the DAC, the last stage is also a filter to remove images or false frequencies. I *think* these images are just from the highest frequencies near the sampling frequency. In that case, considering that there is little information up there, it makes me wonder if you really need that filter at all. Those filters were blamed-rightly or wrongly-for early problems with digital sound due to their steepness and time domain behavior. So presumably, if you ditched them entirely, you could improve the time behavior, at the price of distortion from imaged frequencies. But if there is hardly anything to image, maybe it would be OK. Or at least worth trying out. Now if the images are from ALL the audio, that's a different story. Reconstruction Filter - an overview | ScienceDirect Topics under the section "Hardware for Active Control - S.J. ELLIOTT, in Signal Processing for Active Control, 2001 - 10.3 RECONSTRUCTION FILTERS" it discusses this, but having not thought about this stuff to this level of detail in a long time I could not glean if the imaged frequencies are indeed the ones around half the sampling frequency that is around 22 kHz for a CD system. Actually I spent a fair amount of time looking and couldn't find something clearly showing images of various frequencies on the reconstruction side. (This Typical Errors in Digital Audio: Part 6 – Aliasing was interesting but if I understand correctly they are talking about stuff that's already present before the D/A reconstruction). So back to the topic: what happens with real recordings if there is NO reconstruction filter?