You don't need to use the slave out. It's before the power section.
Okay, here's what I do.... Keep it simple.
I've got an RM100. I've got a Hot Plate. I'm in a situation I can't really record with mic. So I still have my speakers connected to the hot plate and the hot plate to the amp. I talked to the folks at THD about this. I do it this way so I can use whatever effects on the track that I've set up in my rackmount MFX unit (and this saves using some effects plugins which saves processor power).
Those switches for the bright and deep on the front? They work the opposite on the line out. The line out also has a level pot. As you increase your attenuation you'll need to turn up the level pot because it taps the signal after the reactive load.
So basically I take a direct tap off the Line Out of the Hot Plate (I use attenuation at 0 db or maybe 4 db at most), and run that into the input of my Presonus Studio Channel (you can go direct into your interface, but I do some pre-input EQing). Also this gives me some additional control over level. And from there into my interface, making sure the level doesn't clip the interface.
If you run Load or -16 you'll need to turn up the output from the Line Out. I don't have a problem with ground loops. If you do you can always stick a JDI in between the Hot Plate and your interface and use the ground button.
Then once this is set up, slap on a good set of cans, and record your track. You get to monitor your playing direct from your speakers which are loud enough to blow by any "soundproof" headphones with zero latency while you hear the drum track or whatever you're playing along with.
I use Pro Tools. My cab models come from Eleven Free (which comes with Marshall 425 loaded with Greenbacks, and a Marshall cab loaded with Vintage 30s). I also have Audio Ease Cabinet which has 5 more. My favorite is the Greenbacks because I don't have to tweak my tone since that's what I use live.
