A preamp, sometimes called a crossover, is a device, circuit or application that receives, modifies or processes any analog signal that may be sent through it. It's used in recording, fax machines, computer networks, telephone sets and other applications where high quality audio is desired. In addition, many people use preamps to "overclock" their systems so they can get the best performance without spending the time on excessive hardware modifications.
A preamp will generally convert a high-quality analog input signal, say from an FM radio or CD player, into a lower-quality digital signal, say from a DVD player or a digital television. Without a preamp the signal would be too weak or too noisy to be of interest to anyone. There are several types of preamps and it depends on what you need the preamp to do. Let's take a look at four types of preamps and how they perform. You'll also need to decide which type is right for your audio system.
The first type of preamp we'll look at is the mixer preamp. These preamps mix the incoming signal with an external low impedance line-level signal. To make the signal quality better the mixer uses an IC mixer that varies the slope of the slope to allow the different frequencies to blend more evenly. This type of preamp can run on power supplied by the amplifier or it can be run off a separate power amp.
Next is the line monitor or input preamp. This preamp sends the input signal to an amplifier which processes the signal, amplifies it and then sends it out as an audio signal. Line monitoring uses one line for all of the input signals. An advantage is that you can monitor two channels at the same time without having to drive another source of power or line-level sources.
The next type of preamp to consider is the phono preamp. A phono preamp is used when you want to connect a preamp to your phono head unit so that you can hear the music as you listen to it. Phono preamps can be configured to send lower, higher and neutral frequencies. There are several advantages including the ability to easily change the track and adjust volume without turning on your sound board.
Then there are audio interfaces like line level and RCA connections. These types of interfaces will help you to move your signal between preamp and speakers. If you're using your audio interface for an operating system like Linux or MAC you will need a driver in order to function properly. In order to use your interface with Linux you will need to install the pavucontrol driver. Most Linux systems come preinstalled with pavucontrol, but you may have to install it from your system's RPM packages.
The last type of Preamp to consider is the USB powered one. Preamp like the iPhone, iPod, turntables and other hand held music devices usually rely on an external power source. For this reason you should look for a Preamp that uses a high powered USB connection. It is also important to consider a USB power source that will provide ample power for the battery that powers your Preamp. It's best to get a battery that has many hours of charge life, to allow you to maximize your performance.
If your budget allows it then it's worth looking at a mic with a line input. Preamps with Line input offer twice the amount of freedom of using a direct box mic. Line microphones are also usually less expensive than condenser microphones. A final tip when buying a preamp with a line input is to make sure the Mic has a noise reduction feature. This way your voice sounds more refined and will mask any ambient noise such as traffic or a noisy room.