magiccarpetride;581951 Wrote: > I wasn't very clear in my previous explanation: it is not desirable to > use a DAC that will take the bit-perfect digital signal and just > faithfully convert it to analog signal. Why? Because the digital > source, when compared to the same analog source, sucks beyond belief. > The digital source is just a crude approximation, a crass caricature, > if you will, of the original analog signal that got captured by the > microphone and stored on the magnetic tape. Think of a digital audio > source as if being similar to an extremely pixelated photo. The DAC > needs to upconvert the harsh jagged edges into smooth curves. In order > to be able to do that, the DAC needs to be very creative, that is, > built with some ingenuity.
I don't mean to be rude, but... that's pretty badly wrong. If you don't believe me, see the posts by Sean Adams here (the designer of the squeezebox products), or read any book on signal analysis, Fourier transforms, or information theory. Here's the very simplest way I can think of to explain why you're incorrect. Take your jagged-edged signal produced by a DAC and subtract it from the original analog signal. The result of that subtraction is the distortion induced by the A-->D-->A chain. The relevant question is whether or not that distortion is audible when added to the original signal, or whether or not it's as loud as the noise component of the original analog signal. If the answer to both questions is no, then the digital signal will not sound audibly different from the original. A more sophisticated way to look at it is via Shannon, Hartley, and Nyquist, who proved a series of mathematical theorems that tell you precisely what you need to do to encode and reproduce a real-world (finite bandwidth, finite signal/noise) analog signal. The 16 bit 44.1 kHz standard was designed to meet those requirements up to and beyond the level of audible differences, and does so under realistic conditions. If you don't believe me, try distinguishing the sound of a vinyl record from a good quality digital recording (or A-->D-->A processed version) of that same record. Here are two attempts to do that, both failures: http://www.bostonaudiosociety.org/bas_speaker/abx_testing2.htm http://www.hydrogenaudio.org/forums/index.php?act=ST&f=21&t=7953 There are more such tests out there. -- opaqueice ------------------------------------------------------------------------ opaqueice's Profile: http://forums.slimdevices.com/member.php?userid=4234 View this thread: http://forums.slimdevices.com/showthread.php?t=82520 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
