moshulu;131906 Wrote: > For an amateur like me, DACs are mysterious things. After putting > together my Monica2 (a battery-powered non-oversampling DAC that uses a > single TDA1545A chip) I fed in a 2 kHZ “sine wave” signal > from a test CD. I looked at Monica’s analog output, compared > with that of my garden-variety Denon deck (see link to picture below). > I should have anticipated what I saw, but I admit to being shocked. No > way was I going to feed that ugly waveform into my nice, > painfully-constructed, 300B monoblocks! Still, what’s an honest > DAC supposed to do? All it has is the 44.1 kHz data samples; > everything else is guesswork and interpolation. For all it knows, the > original sound WAS a step function. In any case, I figured that the > high frequency components in the steps were probably not going to be > amplified in my monoblocks, transmitted through my cables, reproduced > by my speakers, or heard by my ears. The final proof, of course, was > in the listening. Monica produces a lovely sound, superior to the > Denon deck and, IMHO, to the Squeezebox. > > http://i47.photobucket.com/albums/f165/moshulu/DSCN0563b.jpg > [Top trace: Monica; bottom trace: Denon]
The "smoothing" of the signal done by a modern DAC is not really guesswork. It reconstructs exactly how the signal would have looked during A/D conversion after being bandwidth limited (prior to being sampled) -as it must be to avoid aliasing effects. The output from Monica, however, is the result of "sample and hold", where the sample phase is represented by the leading edge of the steps, and the hold phase is the horizontal sections. Now, the hold phase is just an implementation detail (in DACs), and is not really something that can be said to be part of any stored signal. (In theory, the sample is taken at a specific time, and during an infinitely short time period.) -- P Floding ------------------------------------------------------------------------ P Floding's Profile: http://forums.slimdevices.com/member.php?userid=2932 View this thread: http://forums.slimdevices.com/showthread.php?t=26598 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
