> I know that all best sound is usually tube amps ...
Yes, but that's musical instrument amplifiers. You can often make them sound more colorful and interesting by driving them into moderate levels of distortion. Many tube amplifier circuits have a considerable range of power output during which the distortion remains within, say 5 to 10%, and mainly emphasizes the lower, even-order harmonics of the sound (e.g. "soft clipping").
Microphones are another thing, though. Most of us typically record with a stereo pair of microphones that capture the overall sound of a performance--the entire "mix" at once. So any coloration in the microphone (or preamp, or recorder) applies to everything at once. That approach doesn't usually sound very good; it tends to sound like--well, like a distorted recording, actually.
Even for applications such as close-up vocals in a studio, the problem with using overload distortion in a microphone for "color" is that you usually have no way to control it. With guitar and bass amps, you can set the "drive" level (which determines the distortion) somewhat independently from the output level (volume level). Thus you can pre-set the range in which the desired distortion levels will be triggered. But with a microphone, you can't normally do that; the distortion is a simple function of the sound pressure level. I know of only one contemporary tube microphone that lets you move the overload point up or down within the dynamic range the way an instrument amp can. Much more commonly, that kind of arrangement exists in tube mike preamps. See, for example, ART tube preamps--no great shakes in terms of quality, to be sure, but they have the kind of gain controls that I'm talking about, and they've sold fairly well over the years.
Most "vintage" tube microphones weren't designed for close-up recording at screaming volume levels, so their audible overload range begins at a point below the limit of a rock singer's volume range. That, just coincidentally, allows a singer to use the overload range as an "effect" by screaming into the mike. (And that is pretty much how tube condensers got their reputation as studio vocal microphones during the Beatles era.) There also are people who will gladly, for a fee, modify a microphone's circuitry to bring its overload point down into the volume range that people can sing in, so that a singer can drive that microphone into varying degrees of distortion for effect.
Those approaches tend to yield rather specialized microphones that may work well for one person's voice, but not for another person's. And that can be good enough if you can afford what it costs to take that approach. But again, that's all close-up studio recording--spot or soloist-type miking. It's one thing to color a particular element of a recording, such as the bass or the vocals, but quite another one to smear everything with the same distortion. That gets old pretty quickly.
--best regards
Topic: tube microphones (Read 6059 times)