I have recorded live concerts using Edirol R-09 internal mic.
They were not Rock concerts, and I set the input level = 7 and the result was OK but I still got some cracks during some very loud notes.
In this case, the result would be very soft and I need to change the volume level of the recording with a sound editing application later, though (+400% or more) and reduce the bass.
I have set the AGC on once, but the result was much worse (very annoying indeed, with the volume going up and down unnaturally all the time).
So I would suggest input level = 5 or 6 using the internal mic to record in the open air. If you have to conceal the mic inside your jacket or something, higher input level is OK (7 or
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I put my Edirol inside a thick dark glove, start recording and switch the HOLD on and let just the mic portion slipped out.