I had an old Panasonic boom box cassette recorder that an old girlfriend bought me in the mid 70s with two little built in condenser mics that was amazing.
I would set it up somewhere near the middle of the room and as far away from the amps as I could without having anything major blocking the path of the sound, turn it on and walk away. Everything came out suprisingly good. The vocals would lose the crispness of the echo and/or chorus on the PA, but that 's something that gets lost in just about any tight spaced high volume live recording regardless of what equipment you're using.
Rick