It helps that he's using a Royer ribbon mic mixed with a 57, it gives a really accurate representation of a guitar amp, when placed/mixed even just moderately well. This is a lot like what the amp sounds like new, tube/speaker changes affect it a lot. I don't even bother with most recorded demos, because the mic, it's placement and mixing can drastically change the vibe vs what an amp sounds like in real life. That Royer is pretty awesome for an accurate "in the room" capture, the 57 is usually just used to fill in the upper mids a bit, as that's the the only weakness in the Royer, but honestly you could get buy with just some eq and no 57. To get an idea of how useless demos can actually be, some of the most searing melt your face solos from back in the day were recorded using a small little Princeton or Champ.