This may be irrelevant to loads of people, but it is something I have recently “discovered” on one of my amps.
It’s called “Emulated Output”, I’ve seen this for ages in loads of amps, but it’s a little different on my Blackstar HT-1R, it’s got a 1/4″ standard guitar jack, and this means I am able to use it with my headphones, usually these outputs (at least in my experience) are XLR outputs and they are made so you can connect your amp to a console and get reproduce the sound through other speakers (not guitar cabinets), this is useful for live gigs, however I never liked the sound yo can get out of this. Anyway… going back to the Emulated Output on the Blackstar, I’ve connected my headphones… and I was blown away! you feel that the sound you hear is from a 100W amp at a stadium gig (if you use a little reverb :p).
To my understanding this output allows you to hear the sound that you would get if you could turn your amp to 10 without going deaf or to jail (pesky neighbors) and it is addictive you could just sit and play riffs for hours and still fall in love with the sound, and not only that… you can also plug in your phone to the input and hear the music through your headphones, so you can play along your songs without anyone hearing a thing but most importantly with an impressive quality.
If you don’t have a pair of decent headphones I’ve already recommended in previous posts the AKG K77, they are very decent and dirt cheap. I found that this output did not work well with my Marshall headphones, I think it’s got to do with the amount of power they can take, because it sounds all distorted, so you may need some studio headphones.