FWIW, I have since figured out that it's not safe to say that nearly all condenser mics have preamps.

It's more proper to say that nearly all DC biased condenser microphones, the kind we use in music production, have a preamp that is primarily used to amplify current for the relatively long cable run. I think I assumed it was primarily for voltage gain... but now it seems obvious that the current boost is helpful.

I'm at a stage where I'm trying not to pretend that I understand impedance real well... so I only know the more obvious things about what the transformer is doing.

best regards,
mike

Not to further muddy the water, but...

a transformer can be found at the output of any microphone type (moving magnet, ribbon, condenser, carbon<G>), and it can serve different purposes, from isolation to level shifting to impedance matching.

a preamplifier is most often found in condenser and ribbon microphones, but it could be found anywhere as well. These preamplifiers are intended to bring the very low output level of a condenser or ribbon element up to nominal microphone level, or in a couple of oddball cases, line level.

Some DC powered microphones have circuits that look a little like preamplifiers, but they are really just voltage followers, and they are used to buffer impedance mismatches.

Some DC powered microphones have circuits that look a little like preamplifiers, but they are really line drivers, and they can boost current, or buffer impedance mismatches, or both.

None of which makes all that big a difference, really... the combination of microphone element, capsule enclosure, active and passive stages all combine to make a microphone sound the way it does.

Now specifically addressing the active circuit in a microphone - it's there because the microphone would not work without it, and it has little or nothing to do with the external preamplier. And it definitely does not indicate poor design.

A modern condenser microphone provides a very tiny output. It must be amplified. And some of these elements have an insanely high source impedance, and that must be buffered to prevent the subsequent wiring from swamping it.

A modern ribbon microphone has an output that is almost the same as other dynamic microphones, but the devil is in the details, and that extra 10 dB to 20 dB right at the capsule can be a devil of a detail!

Needless to say, the actual output level from a microphone is directly proportional to the air moving in front of it. If you've ever used a TLM-103 you probably discovered that you could use it without an external preamplifier when you stuck it in front of a drum head or loudspeaker.

Does that help at all?