Alright, I went to Modest Mouse tonight to record. Everything seemed to go fine, I was in a good place @ the venue (right behind the soundboard), mics in hat, venue was a tad bassy but i didn't worry because I had my Preamp this time. Anyway, I finish up get in my car to listen, and the recording is HORRIBLY BASSY. The first show I taped, I plugged my microphone into the "Mic In" and had my level @ like 2, and I still got bass feedback, but not even as much as I did running this time through the Line In. It's odd.
Well, I see I'm not the only one to run into this little problem with this setup (Church Audio omnis + Visivox pre-amp).
I've had no problem with this setup at quieter shows, but haven't (yet) made a superb tape at loud shows.
Which pre-amp do you have, though? The one I have has a lo and a high gain option, which might help me in future... I have only been to two (loud-ish) concerts with this setup, and both times I was stupid and didn't bother dropping to low gain. I got distortion in both cases. The results in the second case were passable, but I have to do some testing to see if the problem is the mics or something else.
You could always do the poor-man's-attenuator trick, and go to Radio Shack and pick up an inline headphone volume control, and drop that between the mic and the pre-amp... but if the problem is overloading of the mics themselves, then that won't help much.