re: This Beatles song really doesn't sound 50 years old.

That was the first song whose sound was engineered by Geoff Emerick, who had just turned 18 before this recording. He put the drum mics dangerously close to the snare, hence that loud snare sound. John Lennon told him something like "I want to sound like a monk yelling from the top of a mountain 10,000 miles away" and of course Emerick had no idea what the hell he was talking about, but somehow he nailed it according to Lennon.