I'm thinking about designing a simple low-frequency AWG for audio work, but I'm struggling to understand what I've read about output filtering when using a DAC to generate waveforms.
If I generate a 20KHz sine wave with a 200KHz sample rate, I know I could have a sharp rolloff reconstruction filter above 20KHz that would remove almost all of the stepping distortion created by the DAC, but if I then want to generate say, 20Hz, how do I remove these steps using the same filter? Depending on the bit depth used, won't the samples take place at different intervals, and produce different frequencies in the output?
I guess another question would be how important is it for general purposes to actually filter this output? Would a simple RC filter with a -3dB at 1/2 the sampling frequency suffice? Especially if I'm using a 24bit DAC anyway.
Hopefully someone has done this before and has some insight, apologies if this has been discussed here already.