Leaderboard

I had time to look up the manual for your amp. There's a footswitch (PEDL-90016) that toggles the FX Loop. Since I don't see a manual switch (usually on the front panel) I would normally assume that the FX Loop is ON by default. However, it would be silly to assume logic from Marshall (like they ASSUME that you have the footswitch, so no front panel switch is necessary...)., so if your FX LOOP isn't working you should spend some time researching that.

How do you dial in your overdriven presets? With my ears - not meant to be facetious, but really that's all that matters. 'Standard practice' is BS, it's just doing what others do and may not work for you. You may want/need to change your mic/cab approach for dirtier sounds, or even the amp settings. Luckily you can do all those changes with one button push using snapshots. I think you need to throw away analog approaches (which frankly were always a massive compromise (amp + cab with pedals in front) and embrace what digital offers in terms of clean and dirty and 'disgusting' can all be highly independent. You are no longer bound to amp/pedal/can settings based on what you have onstage. Play and learn, and have some fun.