I am new to the forum, but I was searching for mod solutions on this amp as I also own one. For someone peculiar on tone as me, this amp has issues, especially if you play live in a small club. This amp could handle small club situations but only on green (clean) channel because this has the only adequate bottom end sound. The orange has a decent overdrive crunch, but bass has almost no adjustment room. The Red channel does horrible things with the 16 ohm thin paper speaker that warrants no attempt at achieving a tone to perform or record with.

These things should not happen to a Marshall amplifier at all or any amplifier that is sold in the price range the DSL401 is in. I did not pay full price for this amp and nor should anyone for that matter, unless you are novice enough to not percieve or listen for these shortcomings, and the name Marshall means too much to you. There really is no use in overdriving those tall skinny tubes unless you could drive more speakers which it can't.

The lack bottom end on lead channels sounds like a fender problem, and it probably is. Perhaps the best solution is a 'blackfacing' of this Marshall or a mod that full developes the green channels tonal qualities, then using your favorite pedal for crunch and distortion.
However, this amp is just dyin' for that 6L6 boost in the orange/red positions. If anyone has help on this let me know.

RV