I've noticed this before but as I haven't really used the blend function, I couldn't be bothered with further investigation. However, the newest update claims to fix the issue:
Kazrog wrote:From the manual in progress, for version 5.0.5 guitar FX:
[*]Fixed plugin delay compensation issue that caused wet/dry signal phasing during blending.[/list]
Well, I decided to do some testing and noticed some strange things happening.
For reference, here's the clean impulse (light blue) overlaid with a simple zero-latency saturation (yellow):
Here's Vintage Driver at 100% wet. Still nothing special here. The slower rise time of the waveform is normal for a circuit emulation plugin I think. 7 samples shouldn't cause much problems when blended with wet/dry.
But here's a GIF where I toggle a 30% mix (to balance the peaks) Vintage Driver through quality 1-6.
There's a significant difference with the dry and wet peaks, and in oversampled (buffered) modes the dry peak is shifted backwards in time.
The plugin reported latency values change accordingly (I'm using 128 samples of audio device buffer):
0 - 64 - 32 - 16 - 32 - 16
Thermionik Blackverb, 100% dry, quality 1 (8spl latency)
Thermionik Blackverb, 30% dry, quality 1-6
Also, Recabinet 5 now seems to report zero latency, instead of 1*buffer. However, here's Recab 5, 30% wet, Dyn ON
The impulse itself naturally adds a bit latency and it varies, but with every impulse I tried there was at least ~18spl added latency between the dry and wet peaks, when the Dynamics was ON.
So, at the moment I wouldn't advice any REAPER peeps to use the blend function until this is fixed.