[Chikuzen]

http://avisynth.org/mediawiki/Intern...trol_functions
OPT_AllowFloatAudio | v2.57 | global OPT_AllowFloatAudio = True
This option enables WAVE_FORMAT_IEEE_FLOAT audio output. The default is to autoconvert Float audio to 16 bit.

It will be changed into 16bit by avisynth itself if you pass float to the tool using vfw interface(e.g. ffmpeg, wavi, etc) without ”global OPT_AllowFloatAudio = True".
And generaly, you should avoid use of global variables if possible.
Thus, avs2pipe(mod) is better choice than wavi if you want to use float audio.