I think the mystic of The Microphone Preamp is on the wane and not before time IMHO.
Back in the day, mics were all dynamics and we only had valves to amp 'em. As now, mics were very low level, balanced and very low impedance. Valves stages are noisy and unbalanced high impedance. The saviour in this story was of course the audio transformer. But you needed high ratios and that meant a poor HF response (typical cutoff 12kHz!). As transformer technology improved so did the response and distortions but at a cost and since most pre amp makers used their own traffs a certain "house sound" emerged. To add even more to the cost the output needed a bigger but still high quality transformer to deliver a low Z, balanced output.
Early transistors were no help, their noise was no better at least than a good traff+triode and they had pitiful headroom (you could build quite a decent transistor pre IF you used an input traff!) .
The coming of the integrated circuit changed all that. An NE5532 was good enough for most applications sans transformer and the now very common hybrid 2 or 4 transistor _ op amp design was better than almost any valve pre for noise, distortion and bandwidth.
So today a very good mic preamp can be made for a couple of $.
The top kit still has its advantages of course. Better gain setting systems, notoriously difficult to do for a wide gain range. Filters, polarity switches and by using advanced techniques and selecting components, the very last word in low noise can be achieved, but few of us have rooms quiet enough for it to matter.
I vividly remember the first "modern" mic amp I encountered in 2005 when I bought a Behringer BCA2000 AI. I would have KILLED for that mic pre forty years ago!
Dave.
