carpa, you wrote:
> I thought that the more sensitive a mic is, the better for the preamp in order to use not too much gain (expecially for not-so-good preamps).
With an extremely noisy preamp or an extremely quiet recording venue that could be true, but it's unlikely for most people here, I think.
Every microphone has a certain equivalent noise level, often 10 to 20 dB SPL or thereabouts. That amount of noise is always part of the signal which that microphone puts out. But microphone sensitivity and noise are tied together in a way that might not be obvious. Think this through, please: If you have two microphones with the same equivalent noise level and one microphone is twice as sensitive as the other, the more sensitive microphone will put out a residual noise voltage twice as high as the other microphone will put out.
It's crucial to be aware of that relationship. With a very noisy preamp, yes--you'd like to "swamp" its input noise with a nice, clean, strong signal from the microphone. But once your microphone is so sensitive that its own noise voltage equals or exceeds the preamp's input noise voltage, then you can't "swamp" the preamp's input noise any further--you'd be trying to cover noise with noise, and that doesn't work.
The same thing applies to room noise, and that's the real kicker. I'm a classical engineer primarily; classical recording sessions are very much affected by any noise from the room or even from outside the building you're recording in. Living in a big city, it's damned hard to find any recording venue quiet enough to let you hear the noise of a modern, professional condenser microphone. Most people here, from what I can see, record in places where the noise of their microphones AND the noise of any halfway reasonable preamp are both swamped by noise from the venue approximately 100% of the time.
If people here were into recording clavichords or certain nature sounds from a distance in ultra-quiet surroundings, using dynamic microphones (especially ribbons), it would be different. But people who make live recordings of amplified music with an audience present, using professional condenser microphones--preamp input noise just isn't going to be an audible factor unless your preamp is total crap. Not only do you not need to drown out that noise with extra oomph from your microphones, you can't do so, because your microphone's own signals are so full of room noise.
--best regards
P.S.: gutbucket, the difference in sensitivity between mike and line inputs on consumer equipment is typically 30 - 40 dB. Consumer "line level" is about 12 dB below pro "line level," but consumer "mike level" is even further below professional "mike level"--the mike inputs on consumer recorders are generally designed for use with low-cost dynamic microphones or electret condensers, and microphones in that class typically have 10, 15 or even 20 dB lower sensitivity than typical professional condenser microphones have. If the R-09 really had only a 12 dB difference between its mike and line inputs it would be quite unusual, and not at all practical for many users.