Unfortunately, it's not well documented! There's also been 2 versions since my post with susposedly subtly different SQ, the last version enabling you to switch between the 2 (A.06). There have been at least 6 firmware updates since launch! John Westlake is very busy designing the B-DAC, M-AMP, M-PAX & at his own admission, isn't too good at documentation!
All I can say is that the updating process on Windows works flawlessly but finding earlier versions might be hard to roll back to. Until someone documents all these changes on John's behalf, it maybe a good idea to hold fire until a final version is available but don't bother looking to audiolab for updates - they don't even have a link to the bitperfect test files the last time I looked. Some versions have had minor bugs but none have caused problems.
Since launch:
Absolute phase invert
SPDIF PLL bandwidth options that have helped those using the Logitech SB having lock problems (Jitter rejection Option)
A workaround for a bug in the DAC chipset that the manufacturer isn't addressing
Mute function pausing playback via USB
Display dimming - either dims the display or dims then display then shows " L A K E . W E S T " after 20"
Powerup to last selected input or chosen input (bug to be resolved)
Universal remote control codes to allow direct access to inputs without having to scroll
The ability to reduce filter options to just 2 during scrolling
(I think that's it!)
Future possible options may include input renaming but may loose absolute phase invert but am not certain about this
The M-PAX is supposedly going to include a beefed-up PSU for the M-DAC, a basic FM tuner & analogue input(s) but not sure if means an ADC or analogue output. The M-AMP is going to use modified class A with a future class D design (JW either owns some novel class D patents himself or has been the inventer - no sure which). I'm also not sure what projects will be marketed by JW as Lake West or by Creek. He has also upgraded the SQ on certain customer units sent to him in the Czech Repulic & intends to continue to do so! On one hand, even John has lost count of the options he's made available & on the other, continues to support a product well beyond the call of duty!