I'm not familiar with the DR-40 or the PFA, just saying you want to check settings. You should have been able to test this at home before taking it out to a concert- if it brick walls at 0 then it will brick wall when you record your home stereo. The 853's need to be supplied with the correct voltage, and if you brick walling your mic in, you at least need to try setting it to line in or plugging into line in instead. Either the mics are getting too much voltage or the recorder is. The reason you can get brickwalling at 0 is that the adjustment happens after the signal has already passed through some circuitry that can not handle the signal. I can't say exactly what it is but you need to try something different obviously, or perhaps you have toasted your 853's with too high a phantom voltage. Have you ever made this rig run correctly?