I am able to record at +10db gain and +20db gain, but at 0db gain I can barely hear anything. The mic sounds pretty bad overall. Recording via the line in seems fine. I bought my OP-1 second hand and it has always been this way, but I wanted to confirm that it due to the internal mic being pretty aweful and not mine being defective.
I got mine direct from TE about a year ago and mine has always been the same way.+0dB is basically useless. I almost always end up using an external mic for any real recording.
Yeah, the internal mic is for emergency use for quick sketches before you forget. If I was designing a custom model for my personal use I would just omit the useless thing, but I can understand why it is there.
Am glad it’s not just me. Useful for sampling quick demonstrations and that scratchy,rub modulation too.
Makes sense to me. “rub modulation” hahahaha…
lol it’s just that bad… “is it broken?” 
recently i realized how bad the SNR is when I tried to do some spare acoustic/vocal recording. It’s passable if you bury the live recording parts in a mix and are careful about mic placement: