OK I have a quick update on this, I've just had a quick squizz at this again, and just designed a pre-amplifier based on just the pre-amp sub-section of the Calrec 1061.
I'm gonna use this as an intro project to making the whole shebang.
Here it is, and it simulates perfectly (although I still haven't finished improving it yet, since it's an exact replica of the original, which is not necessarily a good thing...., with substitutions like 2 resistors for the small gain trimmer - which will be different obviously on the PCB, and some HPF caps which seem to mess too much with the bass response, which I'd like to change) - 2 gain stages, and then an output driver.
I'd recommend using transformers at input and output, but it doesn't appear that's a requirement, as the B210 DOA can supposedly drive down to 600ohms, and at lower gains, the input should be perfectly fine as is (i.e. line in etc.), so the simulator says "hell yes", you should be able to use the output transformer-free if you wish to do so.
There's an almost infinite amount of gain available here depending on how the gain resistors are wired up (as per the 1061 there's up to 70dB on tap! yet there don't appear to be issues going even higher....), but, more to come soon, this will definitely be an interesting little project, as it can also be unity gain for some nice analog warming too.... However, for those following the API Compressor thread, I'll probably try and finish that first 8)
Here is the DOA board that I'm currently happy with too - it's VERY close to the original spec-wise, the only substitution is rather than BFR41 and BFR81 on the output, it uses BC639/BC640, aside from that it's absolutely identical to the original, since the parts are quite easy to come by:
