Yes midi delay is a whole other kettle of fish. The solution to your problem is always direct monitor the Drum Brain while tracking. It's easy to find out is there is latency, just toggle the VST drum Input echo as you play. You'll hear the digital delay. I agree even a tiny bit is annoying with drums. Never had a issue with keyboard.
So I keep my kit patched into my monitor mixer and keep input echo off on AD2.
Back on topic.
- Milliseconds X the sample rate = # of samples In the example, if the delay between a pair of room microphones and a soundboard feed in the record's home studio is 17 milliseconds of delay (based 17 feet of distance), the formula becomes:17 times 44.1 = 749.7 samples.
In this case, the recorder enters a sample delay of 749.70 samples into the software for the closest source to time-align the sources.
- Samples divided by the sample rate = milliseconds
- so if a loopback test track is out by 44 samples it is about 1 ms not really noticeable, but a track out by 440 ms is 10 ms so would be very noticeable. This is why the loopback test is important and even if you don't find anything out of sorts I think it's important to understand your system and how it's performing. In my case both my interfaces were only out by under 10 ms so there was not great need to adjust the timing manually.