The signal that a microphone picks up is actually very low, and needs to be boosted for it to be used with your recording device. This is exactly what a mic-preamp does; it boosts the signal to a level that is useable for recording. Initially, you'll probably want to use the pre-amps built into your mixer or interface, if you happen to have either, as it will save money.
However, these kinds of preamps are often of a fairly low quality. Basically, with mic preamps, you pay for sound quality. Musicians after the absolute best quality sound could well spend $3000 on a preamp. If however you are just starting out and have perhaps a budget of $1000 you could use the preamps on your mixer or your audio interface. It's not only budget that affects the output quality on the preamp, you must also know how correctly set levels etc.
Let's talk a little about the features you'll find on most mic preamps, and some tips to ensure you get the optimal sound. Input - Set the input to high as possible providing the meters are not crossing into the red. Having the levels reaching red is introducing distortion, which is going to go through the entire signal path. Meaning that when you listen back to your recording on the computer, you're likely to hear a lot of crackling noises. So again, push the signal as high as possible but do not let it enter the red. Pad - This is a great feature if you are recording sounds other than guitar.
For instance if you were to mic a loud sound source like snare drum even with the input turned all the way down the levels may still be hitting red. Select this feature and it will help to tame the sound further and make it useable. Phantom Power - This is a power source that is sent through a mic cable to a microphone that needs it, such as a condenser mic. It's good to note that some fairly cheap preamps only offer +30v, and some condenser mics may not perform to their best at this level.
It's nice to have phantom power built in to your mic preamp otherwise you would have to get a separate phantom power source. Number Of Preamps - This can range from one single preamp right through to eight preamps in one box. What you are recording will generally determine how many you will need. Vocals are usually recorded in mono, whilst acoustic guitars could be recorded in stereo. Perhaps you are recording an entire band and require one for each amplifier and vocalist, along with several for the drums.
High Pass Filtering - This generally means that all the highs will pass through while the lows are cut. Mics pick up an astounding amount of bass so this is a great feature to have. Of course, this can be corrected using software, though you may as well resolve the problem at the source so you don't have to worry about it later. Hopefully this has given you an insight to what a mic preamp does, and what features to look for when shopping around. Have a read through the bullet points again and compare your list of needs with the features of available on a variety of preamps. Hopefully you will be able to find a product that suits your needs.
Ian Marples has been playing guitar for over 10 years, and now runs the website http://www.uncleslinky.co.uk to help other guitarists learn how to succesfully record music at home. For similar information to this article subscribe to his FREE Newsletter by sending a blank email to firstname.lastname@example.org