Folks, I’m reading an introductory book on DSP for audio and computer music (ISBN 0-8053-1684-1 page 287).
One of the sections discusses oversampled D/A conversion at the output of the CD players. The original signal at 44.1ksps is digitally interpolated to 176.4kHz (4x the sampling frequency) before the D/A.
> That image is centered at 176.4kHz, way beyond the range of hearing, and it doesn’t take much of an analog filter to do a good job removing it (but see Problem 4).
> Problem 4: The first substantial image of the baseband signal in a CD player after oversampled D/A conversion is well beyond the range of human hearing. Why is it still important to filter it out? (Hint: It helps to know something about electronics here.)
My ideas for the answer. (1) The audio amplifiers may be nonlinear at high frequencies, and the nonlinearities from the high frequency signals may show up at the audible band. (2) EMC. But I doubt that EMC is the answer.
