00940: Balanced operation, as AMB points out, is not very popular. We discussed this during the PPA design phase and concluded that if you want true balanced operation you can use only the left and right channels of 2 boards.
With regards to the layout, I will try to align all the MOSFETs if possible, with the input circuit on one side and the capacitors on the other side. This would allow for one big bar bolted to all of the MOSFETs, but would not be conduicive to bolting them to the case wall. The Aavid extrusions require about 1.5 inches of linear space, that's 9 inches for all 6 if they are lined up. It may be that we will either have to sacrifice the Aavid extrusions, or rotate them 90° to reduce the length of the footprint.
Sovkiller: Team M³ is designing the M³ with DIYer input and arranging for board manufacture when the time comes, as a community service.
Earwax: As you say, crossfeed is best left to daughterboards. As Tangent hinted, we will probably include PPA compatible daughterboard holes.
Aos: OK, relatively wimpy by comparison, then.
I don't want to consider any output device less than 1 Amp. May I ask if you have tried the IRFZ24N and IRF9Z34N MOSFETs? We tried the Renesas MOSFETs (if I remember correctly) and didn't find them superior.
Regarding the non-standard FETs, I knew that would come up.
That capacitance multiplier might not be used. It has yet to face close scrutiny by Team M³. To answer more directly, the 2N5457 and 2N5460 have a low, consistent Idss of about 1mA which makes them convenient for this purpose. I was just suggesting to AMB recently that people would not be happy about this and that we could use other FETs or at least use the N channel on both rails by turning it 180° in place of the P channel FET.
MOSFET bias is adjustable, with 80mA being the minimum we are considering for now. Once prototyping and testing has proceeded to a more advanced stage, we will study distortion .vs. bias to determine the optimum value.
JCX: We said no compromises for battery compatibility
, which to me means compromises like low quiescent current, class AB output, keeping the amp to a portable size, etc. The power supply is still very open ended. That is one of the issues we intend to discuss. I would get into more detail right now, but I am late for a movie. I'll be back in a few hours.
Oh, and Jamont, going back to the eurocard format issue, perhaps that is best left to PPA v2. No, there is no info on PPA v2 at this time.