Been doing a lot of audio tests. Found some interesting things, some fairly important for audio/music engines. Still have a lot more tests to do, but I’m taking a breather and posting this:
(click to see full size)
Just some DAC characteristics that I didn’t think about. Normally, you see a lot of “return of zero/centerline” with PCE audio and tests. As in, the leaning of the samples (relative to the audio line) would point towards center line, relative to which polarity the sample it current residing. Especially for sample stuff, because of the low frequency of sample updates (and strings of duplicate samples in a row).
This pic is of a snare sample. It has a lot of sample updates (non redundant runs of samples). If you look at the red lines on the top channel, you can see the slant is towards the next sample, not centerline (green). It’s the channel’s DAC ramping up (and down) voltage to the next sample. Pretty much just like oversampling (or linear point filtering), except this doesn’t happen on the PCE if the sample update is too low. Lower than 7khz. It makes certain samples on DDA a tiny bit softer on the real system too. Just something to think about.