Suzuki-san confirmed this was for dac or phono board when I talked to him at the show. You should have asked me that before, I would have brought it up! Also he confirmed the dedicated low voltage supply for the addon board.
Jude got other things confirmed when he visited Stax office on Friday (such as power supply regulation), I hope to see some news posted in the HF thread at some point.
I liked what I heard on brief listen when compared to stock 727 amp, it felt more significant than differences between other stax amps. Of course, this is to be taken with a pinch of salt given the short audition / show conditions etc...
Oh, and it does look very nice in person, sand blast finish on the aluminum panels, reminiscent of the SR009. It's bigger than other stax amps but nothing compared to my BHSE, I can see people wanting this.
Arnaud