sounds odd... and certainly not an issue ive faced with playback
you need to narrow down the problem slightly.
play a simple sine osc to output - check this is not
if this is distorted, look at your gain levels on output etc.
if not, then we know its not axo hardware related, since the audio output path is ok
so you need to check the wav file, ensure it is a 48k raw 16 bit mono file.
(various threads on the forum about preparing raw files for playback with audacity etc.)
use a scope on the output of table play, check to see if its clipping, if not, try to add a gain after, to reduce gain level.
another 'tip' in patch settings, try turning off 'saturation', which increase gain on patch, if your patch has high gain levels/combines a few audio sources, this can be problematic
to get further, you probably need to post your patch and wav file.
also it'd be useful to see a screenshot of the scope connected to the play, so we can see if its clipping.
I cant say anything about the mics, except there is an audio in config object which you should look at to adjust gain etc.... again, I use axo as an fx with audio in, without any buzzing etc.