Stereo Tool

So, is it the old version now that works or the new one? Since you previously said that it crashes?

Please try minimizing that other screen, or move it out of the way.

It's the new version, that works (Audition on Mac). The old version was still in the Audition effect browser when I tested it the first time. But the new one is OK. The other screen cannot be minimized, it can only be closed. I have to move it down to the bottom of the screen. Maybe your plugin produces an own popup and doesn't use the "effect popup" of Audition... The AU plugins are opening in one screen.

I made a short test regarding to the sound Quality... when I apply the effects of your plugin, it works. But I can`t prefade listen (activate your plugin, choose a preset and play the tracks in the background to find the right settings).

Ah, so the new wxWidgets fixed the El Capitan problem? Great!

The latter is most likely caused by buffering issues (I haven't heard what it sounds like, but if it's chopped up, it's that).
So, try increasing the buffer size in Audition.

Or, if you can't find it quickly, another thing to try is to lower the Latency setting in Stereo Tool under Configuration -> CPU & Latency. This will reduce the audio quality though.

Yeah, one Mac problem seems to be fixed...
The chopping problem stil exists. I`ve increased the buffer size of Audition to the highest value. No fix.
To lower the latency... well, the sense of using Stereo Tool is to increase the audio quality, so that`s no the best workaround I think...

No but it would be useful to know if it helps.

Tested it with lower latency and quality settings - no effect. Sound quality remains bad, but the song now plays slower in prefade listening...

Weird. For Stereo Tool it doesn't matter if you're processing for live listening or to write to a file. It doesn't even know which of the two is happening. If you're processing and saving to a file, does it take a long time? Alternatively, if you turn all the processing off (RESET -> ALL AUDIO SETTINGS), does that fix it?

No, a reset of the audio processing doesn't fix the problem. Applying an effect to a file takes a long time (up to 10 seconds), while applying an AU effect takes about 2,3 seconds.

I understood from Mathijsco that on his system he sees the same issue, but the stand alone version works fine. So it has to be something specific for the VST version...