I contacted Sony Support to figure out exactly where the PCM-M10's Low Cut Filter rolls off the bass. Here's the answer I got:
"Lo cut filter frequency starts at 200Hz, 24dB/Octave filter, effects both Mic and Line input"
200 Hz seems pretty high, but I'm wondering what the 24dB/Octave filter means. Perhaps one of you more tech minded members can explain it to me? Does it maybe mean that although it starts at 200 Hz, it's a gentle roll off curve?
I've used it for several shows and it doesn't seem much more severe than the 80 Hz rolloff on my Tascam.
Also, for anyone who is interested, the LCF filter, when switched on, functions through both the LINE IN and the MIC input. This is super handy when your mics/batt box don't have a any built-in bass rolloff.