Reply To: Debunking the Digital Audio Myth: The Truth About the ‘Stair-Step’ Effect

June 5, 2023 at 3:20 pm #5841

You can recover a sine way just below the Nyquist frequency, say, 20 kHz, just as easily as you can recover a 1 kHz sine wave.


Well, for the EE designing and building the LPF that comes after the conventional DAC running at 44.1 kHz sample rate, it’s not just as easy.  Differentiating 20 kHz from 22.05 kHz is harder than differentiating 1 kHz from 22.05 kHz.  One case is 4+ octaves of spacing and the other is far less than an octave.  To leave the 20 kHz mostly unmolested and to kill its closest image at 24.1 kHz requires a pretty sharp LPF with a skinny transition band.

Now you’re right, Bob, regarding ΣΔ technology and oversampling by 64x.  At 3 MHz sample rate, smoothing out 20 kHz (while leaving it unattenuated) is just as easy as 1 kHz.