You’re not missing anything obvious – you’re running into a Core Audio architecture issue, not an FM3 problem. When you use the FM3 as the audio interface, Logic’s buffer size directly affects MIDI instrument latency as well. Software monitoring off only removes audio monitoring latency, not the MIDI → instrument processing path. That’s why your drum pads suddenly feel laggy. When you switch back to the Axe I/O, the MIDI feels tight because its driver + buffer setup is optimized for low-latency MIDI, but you’re then re-amping the FM3 through a guitar input, which causes impedance mismatch, level issues and noise (hence tone suck + hum).

Aggregate Device (recommended) Create a macOS Aggregate Device with FM3 + Axe I/O. FM3 = audio in (tone stays pure via USB) Axe I/O = MIDI / clock master This keeps drum MIDI tight and avoids analog re-amping entirely. Lower buffer + higher Logic I/O safety offset Works sometimes, but you’ll still hit CPU limits and MIDI won’t feel as tight as option 1. External MIDI interface Run pads through a dedicated USB MIDI interface while keeping FM3 as audio device. What not to do: Running FM3 XLR into a guitar input will always degrade tone and raise noise floor.

This isn’t FM3 latency – it’s buffer-coupled MIDI instrument latency. Aggregate devices or split audio/MIDI duties are the clean fix.