Played with MixPre-3 II few hours yesterday evening and here are some quick personal critical impressions:
The biggest problem for me was get AA batteries out of sled. Not too user friendly design. The solution - place thin ribbon under the batteries. This usually helps in similar situations to get out batteries from holders.
AA batteries is a total shame. Instead of 4xAA they could design sled with SINGLE 18650 li-ion battery and it will produced same Wh capacity.
Battery sled may looks thin, but subjectively seems it is not cheap ABS plastic. It feels like made of Polyamide or similar heavy duty heat resistant Nylon-like industrial material.
XLR lock handles are very tiny and with sharp edges. Not too comfortable to press. Sort of idiotic design way to fit everything inside slim size to provide 5mm less body thickness.
As expected, preamps sounds slightly different between MixPre and MixPre-3 II because transformers technology is very different between them.
As expected, when you plug MixPre out to MixPre-3 II Aux line in, and record with 32 bit mode, you can not recover similar ultra wide dynamic range clipped data as from native MixPre-3 II peamps recording. But it is still better than 24 bit recording because MixPre still allow to recover very tiny amount of clipped data. MixPre was calibrated with 20db tone signal and tested with limiters turned OFF.
Until you create Presets for different connections it is impossible to switch things and setups as fast and intuitive as with MixPre physical buttons.
For some reason "switch to USB files transfer mode" hidden too deep. You need too many clicks inside menu every time when you connect it to computer and want to transfer files.
Faders knobs rotate very smooth and well damped. Input gain faders are fully digital, so they can not change input gain in real time with same smoothness as analogue MixPre faders. When switched to final mix volume control mode, they probably provide more smoothness but i don't tested it yet.
Вespite all this MixPre-3/6 II is a great tool and no any real alternative to it.