Six channels: two from built in mics, two from XLR, and two from 3.5mm jack on the side. Or four channels from built-in mics and two XLR. Recorded as three stereo pairs.
One mystery is how you set the XLR for mic or line level input. Most recorders have a mic/line switch. I didn't see one on the R-26.
You set both the PIP and input sensitivity of the XLRs via the touchscreen. Well, rather, you turn phantom and PIP off/on and then set the input sensitivity. Same concept as on Edirol R-44. It doesn't have "MIC/LINE" like the 680 does.
The only thing I dislike is while you can turn the minijack sensitivity all the way down, I"m not sure if even at its lowest setting it is still a true "line-in".
I have run the Aerco as well as an SBD feed into that jack with no issues though.
Not sure what would cause the issue mentioned re: the MP-2 other than that the input sensitivity must have been set too high.
One thing I would not do is use that auto gain stuff. Just as dumb as using that stuff on another recorder.
Also: as to the HOLD/OFF switch - it will not turn off while recording. If you are turning off HOLD and accidentally push to OFF it tells you you are recording and denies the command.