I can't say that it's necessarily loud enough to jam with a drummer, but I'm not sure. It's more than loud enough in my room and I have a Marshall 100W and VOX AC50 in my room. It seems to get as loud as those do when they're on 3 or 4 on the volume pot. I'm running it into an 8ohm cabinet with two 10" Jensen speakers.
The best part about this unit is the sound. The bass, treble and mid knobs really shape the sound. I'm used to bass, treble and mid pots shaping a sound on an amp, but I feel like these actually make a huge difference.
I owned a Roland JC120 for a decade and this unit, which I have running into some vintage Jensens, sounds like a Roland JC120. But the treble, bass and mid pots are actually more responsive, so if you want it too, it can sound a JC120 that had a baby with a Fender Deluxe Reverb. The nice thing is, it doesn't get in the way of your tone. Like the Roland JC120, it just feels like more of a faithful recreation of your tone. But, the mid pot actually makes a big difference, so if you want to scoop the mids, and pump up the bass, the knobs ACTUALLY FREAKIN' DO THAT. I was hoping for a flat response amp for my modeller and it IS that. But even without a preamp or a modeller shaping the tone, it's absolutely phenomenal.
The gain sound is great. It's like a soft rounded drive, not a distortion. If you want anything gnarly or nasty, you'll have to add a DS-1 or a distortion pedal. The gain is more like an even-keeled OD-3 or bluesdriver tone, but maybe with even LESS frequency shaping which is kind of nice. The gain just beefs up the tone in a nice even way. So it's perfect for edge of breakup tones and gets you pretty far into rock territory before you start looking around for a distortion pedal. If you're into Indy Rock, New Wave and Early British Punk, there's more than enough on tap.
The Reverb sounds perfect. There is nothing I would wish to improve on the Reverb sound.
The only thing I wish they would improve (or perhaps I should say offer) is to make a 40-50W version, or a 100W stereo version. One with a gain channel switch. I'd pay $200-$250 for something like that having heard this version. Having heard this, I want more. I may split the Jensens and buy a second one, so I can power each speaker independently and make my own stereo rig.
Oh, I should say, if you're jamming with a quiet drummer, or a drummer with electronic drums, then this is loud enough. The drummers I'm referencing were very loud rock drummers.