No, more channels would not help…
That animation shows, how analog signal looks like if one aproximates square wave with sine. It gets better as one uses more and more sines, but look at the end of upward and beginning of downward part. There is considerable up for short time, before it settles at desired value. It is inevitable….
Simply, perfect square wave does not exist in analog world.
The summing in the picture is just mathematical abstraction, not real summing in the gear. If one creates square wave in digital, it has infinite number of sines reaching infinite frequency (if using infinite sample rate)… But because of limited samplerate, digital may represent just frequences up to half of sampling rate. In fact, D/A generates higher frequencies, but they have to be cut off after conversion to analog, they are just “reflections” of lower frequencies.
There are few peculiar things in D/A and A/D that are not very intuitive. It is just pure math…
But back to original topic… I guess, there is not much difference if the summing of signals is done analog or digital. Beside, that analog summing always introduces some kind of alteration/colouring of signal (probably unrecognizable, but still present), while digital does it just perfectly. Unless one deliberately models analogish sound in digital summing…
