Sorry, reading back, I get the recording situation more clearly now.
It really does sound like the signal from the turntable is at fault, whether that's due to the turntable output itself or the RCA cables. It's possible you brickwalled, if the recorder's input is more sensitive to bass frequencies, maybe. But either way, you accurately recorded a distorted signal.
If the "crunching" is all in the upper frequencies, you could try the high pass filter on the turntable feed and compensate by cranking up the higher frequencies on the mic recording. How that sounds is going to depend on how much of the audience chatter is in the high frequencies, but it's worth a shot.