Thought this deserves its own thread. Audio amp designers (and testers) use square waves in testing because they can see the amplified square wave and get an instant insight into what the amp is doing. Square waves are very hard to amplify, as they are the infinite sum of an infinite series of sine waves.
The 16/44 vs 24/98 thread talks about square waves at 20kHz being sampled. This is at best misleading. For two reasons: 1) music doesn't have any 20kHz square waves 2) you can't sample a 20kHz square wave, per Nyquist's fundamental rules. I think #2 deserves a bit of explaination. Before you can sample any signal, you must pass it through a low pass filter set at the Nyquist frequency. For 44.1 kHz, the filter has to pass signals below 22.05 kHz, and block all signals above 2.05 kHz. Once you've filtered the incoming signal, then you can sample it. But, what is not obvious, is that when you pass a 20kHz square wave signal through a 22.05 kHz low pass filter, the result is a sine wave signal at 20kHz. It may have some spurious harmonics, but the basic output is a sine wave. When you sample the sine wave, you get a stream of bits. When you pass the stream of bits to a DAC, you get a sine wave. You do not get a 20kHz square wave. -- pfarrell Pat http://www.pfarrell.com/music/slimserver/slimsoftware.html ------------------------------------------------------------------------ pfarrell's Profile: http://forums.slimdevices.com/member.php?userid=200 View this thread: http://forums.slimdevices.com/showthread.php?t=38813 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
