MXL Tube Microphones
The most interesting thing about these microphones is the way that they inherit their personality and color from their tubes. The MXL Genesis Studio Tube Condenser Microphone, for example, contains a genuine Mullard 12AT7 tube that gives it a stellar combination of clean highs and warm mids with a tight, satisfying bottom-end. Tube microphones can be as crystal-clear, as dark or as warm as you like; it's just a matter of choosing the MXL mic with the right tube for those qualities.
Naturally, there is one big advantage with a tube mic, which is that you can give it a completely new sound simply by changing the tube. That makes them nice and versatile: no need to buy multiple microphones when you can simply shop for replacement tubes that will give you the voice you're looking for. Just be careful to match the type; for instance, if you're using the legendary MXL Revelation, any replacement tube would have to have the same footprint as the EF86 pentode it comes with. Of course, when you hear that tube's warm, rich and transparent sound, chances are great that you wouldn't dream of swapping it anyway.
If you do some research, you'll probably encounter some people claiming that tube mics are universally better or worse, but neither of them would be right. The truth is that every mic has its own personal voice, whether it's based on tubes or solid-state circuitry. So, don't dwell on the fact that MXL tube microphones are based on vacuum tube tech. Instead, look at the features and sound characteristics that make each one unique. Make your decision based on those factors, and you'll have no trouble choosing the perfect tube mic for your needs.