You also brought up an interesting question about op-amps…. It’s interesting because contrary to what you might expect, there has not been any improvement in analogue op-amp design for years, and yes, I have been trying all sorts of types for the new mic amp and guess what…. I have come back to the MC33078. It may be about half a dB noisier than the LM833N or the LM4562, but it is readily available, reliable and stable so I like it! And with a good mic amp, the noise you are hearing is predominantly resistive noise from the elements of the mic itself. In the new mic amp, the electronic noise from the mic amp is actually at least 8dB below the noise of any mic I try. The big advances have happened in measuring techniques…. I can now measure noise and distortion far better than in the ‘old days’!
And ribbon mics can be a pain! I must look up the ‘FetHead’; that’s something I have not met. 