Very cool, so did you get the hum sorted?
Love that site of projects, and I'm not kidding, when I get things sorted and have time to relax, I'm gonna build an SSL bus compressor. Love the sound of that thing. It's one of those pieces of hardware that is truly iconic for a very good reason, it really does work magic on recordings!
Regards making a modeled version in Axoloti, it's a shame it would take too much processing power.
I could be wrong (and probably am) but i get the feeling Johannes and Mark might be secretly analyzing the shortcomings of the current Axo and planning a newer model that eliminates or lessens them. Personally, I wish the physical aspect of Axo was just a board with no sockets attached to it, or at least give us the option to buy one unpopulated.
For example, I don't like the stereo out being on a single jack. It's no doubt done for space reasons, but if there was no need to attach anything directly to the board, we'd be free to attach our own choice of jacks etc. Same with power, same with input, same with card type, we'd be able to attach our own much like you can do with an Arduino or a Raspberry Pi Compute or Zero module.
I think it also needs to cater for multitrack recording and playback and sampling in a much more elegant way than it does right now. I think demand for sampling and multitrack recording is one aspect of the Axo that was maybe underestimated in the current design.