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I also note that Pro Q2 VST2 and VST3 save and recall processor state, as does Pro Q3 in VST2, however Pro Q3 in VST3 does not save.
![fabfilter pro q2 gb fabfilter pro q2 gb](https://procracked.org/wp-content/uploads/2021/06/images-3-1.jpg)
What I find is that Fab Filter Pro Q2 has correct PDC behaviour in VST2 and VST 3 versions, but in Pro Q3 VST2 works fine whilst VST3 does not compensate when switched between processing modes. created a track with stereo song, duplicated that and phase flipped the copy to phase cancel in Monitoring. I have just done my own test, similar to yours. firstly there is a known issue with PDC in Loop Play, this is on the fix list, so any tests done whilst in Loop Play would be misleading. I also did this and the vst3-versions of plugins were not latecy DTB, thanks for your post. Maybe someone can confirm this behaviour and use another vst3 plugin (should introduce latency which mixbus should compensate). instead after mixbus restart the default processing mode (zero latency) was applied. in my case the processing mode of the plugin pro q3 was not saved with the session. Someone else in this forum reported that some settings/params of vst3-plugins are not correctly saved with the session. I did not set an eq-curve in pro q3 just changed the processing mode. the signal was completely nulled when using vst2 but not with the vst3-version.ītw. I even checked nulling by flipping the phase on the duplicated track. I repeated this test with Pro Q3 VST2-version and - guess what - everything works fine. the delay is gone when switching off the plugin. switching pro q 3 on/off confirmed this behaviour. Then I switched to linear phase-medium which introduced a latency of 106.7 ms and this could be clearly heard as a slap delay - once again imo no latency compensation - the signal was behind the original track. so mixbus seemed not to apply a plugin delay compensation. Switching to processing mode "natural phase" caused a latency of 320 samples (according to the info at the left-corner of the plugin pane) - sounded like a short "doubler" effect. Inserted Pro Q3 on the duplicated track with default setting (processing mode=zero latency ) which did not introduce any latency and everything was fine - no issues. I duplicated a snare track and routed both directly to master bus. I did some testing with fabfilter PRO Q3 (VST3 version). seems as if these are not fully latency-compensated by mixbus 32c (I am on win10 pro, mixbus 32c v6.2.70). I would like to let you know my experience with latency compensation of vst3-plugins.