Update - After troubleshooting further I discovered that the problem described below is tied to AutoEQ, BassEQ, and Low Level Boost. If one, two, or all three modules are enabled, the problem below will occur to some degree. Only if all three of these modules are disabled will the problem below not occur. This problem occurs going all the way back to the version of Stereo Tool where each module was introduced. See viewtopic.php?f=14&t=23663&start=520#p54980
Checking the latest beta 61, Stereo Tool VST is having problems for me.
I did some additional checking and this problem is present back to at least beta 49. Wish I had more time to keep checking further.
This issue is that not all Stereo Tool modules seem to completely engage until either some amount of audio is processed, or the VST is used at least once in the current DAW session.
Here's my original track:
Here's after running Stereo Tool on it once (note first part of track):
Here's after clicking "Undo" in the Edit menu, then running Stereo Tool on it again without changing any settings:
I checked and I can't seem to find exactly which modules are the culprit. I suspected "Low Level Boost" but that's not it. So I give up. I wish I had more time to troubleshoot further but I don't right now. (I'm not even using any of the compressors here.)
Start Audacity (I'm on 2.2.1 but this shouldn't matter).
Load the following track (it's public domain): sample.mp3
Start Stereo Tool, import the following settings: User_Default_b61.sts
Apply Stereo Tool. Note result (take screenshot, etc.)
Undo Stereo Tool (Edit -> Undo)
Apply Stereo Tool again. Note result.
I checked on another DAW (Wavosaur) and reproduced this behavior there, so it doesn't appear to be a DAW issue. Checked both 32 and 64 bit VST (in 32 and 64 bit Wavosaur) with same results. Also checked 16 bit vs. 32 bit wav, that had no effect either. The last thing I had time to check, was enabling the "VST Workaround - Clean Buffer at start of new track" option; this also had no effect on the issue.