M2x powered from DC source

no challenge

just stay with your limits 🙂

do not exceed max capacitance on output of your reg

if needed ( try!) and if confirmed with listening that is going to better - you can include additional capacitance , but always preceding with some small series resistor

so - say that you can put 0R22/3W-033R/3W in rail in series , then your parallel cap

it could prevent oscillation in reg
 
Well, that's pretty easy advice to follow. The nutube will be the thing to push it over the edge if anything does, based on all those 1kuF caps.

If necessary I can move up to the bigger reg. Will first push the 400W ABB and see what it does then bring the battery into the system. Exciting stuff :up: