SS Pre into SS Poweramp?

[mexicanyella]

I'm not the OP, but it wasn't really a project, at least based on the original question and yours...just plug your Marshall's line out/FX send/whatever into another amp's line in/FX return jack. The Marshall's preamp tone will now come through both amps' power sections and speakers: amp slaving.

It's definitely worth it if you like the master amp's tone but want more volume, and you have a suitable slave amp sitting around. I have had lots of fun doing this with a little Peavey amp I like as the master amp, slaved through various different amps.