What Is A Preamp And Why Should I Care
Let’s start broadly with the title of this discussion. In a few sentences, what is a microphone preamp, and why should we care?
Geoff Daking: The simplest description is that a mic preamp receives the tiny voltage output from a microphone and brings it up to a more usable level.
John La Grou: A microphone preamp is a voltage amplifier and current buffer. It can boost mic output levels by 1000 times or more, while sourcing a significant amount of output current.
Dan Kennedy: It starts at the microphone, which is amplified by the preamp to line level, which is compatible with compressors and equalizers (if used), which then feeds the A/D converter or tape machine input.
EveAnna Manley: Also importantly, the input of your microphone preamplifier has to be able to accommodate different levels and impedances that various microphones will present to it. So your microphone preamplifier needs to amplify with utmost fidelity and be flexible enough to work with a variety of microphone outputs.
Geoff: This is a delicate process, because we require a very high level of integrity in the process. There are many devices that amplify small signals—radios, for instance—but we do not expect them to have the same standard of performance.
Michael Grace: I think we mostly don't give it credit for what it really has to do. First, the microphone preamplifier has to have an exceptionally wide gain range to be useful. From a quiet whisper on a ribbon mic to a loud roar on a high output condenser mic, we are talking about an input voltage range of more than 1 million times. The mic preamp has to accommodate that range of signal and feed it to your recording device at the proper level without degrading your sound.
Todd Humora: It is a critical first stage, because any noise or character in that stage will be amplified with that gain and be present throughout thereafter.