Right. This is going to be an odd one.... I don't yet have an audio sample, so bear with me.
Taped a band called Helsinki last night at Dingwalls in Camden. Great set, not the best venue sound. Checked the recording outside afterwards, and it sounded GREAT. Really pleased.
However... listening to the full show on the way home, and halfway through the quality dips really obviously. It's still listenable, but half-way through a song the dynamics are gooooooooone and it's suddenly flat for the rest of the show, all muddy.

I've had a quick mic check, all seems fine. Cables seem fine too. Checked the R09's line in, seems fine - I believe if my i/p had given up the ghost I'd have noise and/or drop-outs. None of those.
Volume is consistent, and I'm positive I've not changed settings midway, on either the pre (my FEL BMA1) or the R09.
My question, therefore, is - does this sound like the pre battery might have started running out mid-show? I'll get a sample up tomorrow, but I'm taping again tomorrow night so I'm desperately hoping that a simple battery swap will fix it.
Does a preamp battery run out gradually or would it explain the sudden change? Could I have a bad battery? I've used the same battery for 4 shows now, and it's the only thing I can think of that could be at fault at this point.
Any assistance would be greatly appreciated. Cheers folks.