Audacity 2.3.1
Windows 7 x64 SP1
When applying a VST effect using a VST that was exported from Faust DSP code, the VST always uses it’s defaults - regardless of adjustments.
Other VSTs from elsewhere work correctly in Audacity.
But in another editor application (Wavosaur) the Faust VST functions correctly!
I compared Audacity 1.3.12-beta Unicode, and it behaves the same way as 2.3.1.
Is this an Audacity bug, or is it a Faust VST export bug?
Short answer: I don’t know 
TL;DR
Audacity’s VST support is based on 3rd party open source VST headers (rather than Steinberg’s VST headers, which have a restricted license). While this generally works reasonably well for a large number of VST effects, it has limitations.
Audacity is not a full-featured VST host. There are many VST features that are not supported, notably (incomplete list):
There are also problems with LV2 and LADSPA effects created with Faust.
I have successfully run some very basic LV2 / LADSPA effects from Faust in Audacity, but most times they don’t work properly (or at all), even if they work in other applications.
It would be very nice is Audacity and Faust worked better together, but the Audacity development team is very small, and there are many more pressing issues competing for their attention.
Hi Steve,
I’m not sure if this helps narrow it down, but I am told the Linux 64 versions of the VSTs do work correctly in Linux Audacity. None of this “always load the defaults” problem.