In this thread a builder tried mixed mode feedback but later abandoned the idea.
http://www.diyaudio.com/forums/pass-labs/248030-aca-5w-guitar-power-amp.html
The ACA has an output impedance of several Ohms when the feedback is disconnected so it sounds just fine as a guitar amp.
http://www.diyaudio.com/forums/pass-labs/248030-aca-5w-guitar-power-amp.html
The ACA has an output impedance of several Ohms when the feedback is disconnected so it sounds just fine as a guitar amp.