What Is a Stereo Preamp?

By Joe Fletcher

The term preamp is short for preamplifier, which is one of the key components in a stereo system. The preamplifier performs a range of functions and is the most active, responsible part in your stereo. Here's a further look at exactly what it does in relation to the stereo system.


The preamplifier is the main control system for your stereo. It serves as a middleman between the audio input, such as a CD player and the amplifier. The preamplifier receives and processes the input signal from your CD player or other audio device, increases the voltage to line level when the input signal is weak and sends the signal on to the amplifier. The amplifier adds the majority of power and outputs the powered signal to the speakers.


In addition to its primary funcion processing the audio signal, the preamplifier houses the inputs and controls of the system. All your inputs are connected to the preamplifier and simple adjustments like volume control, program mode and balance are the domain of the preamplifier.


In many stereo systems, a receiver is used in place of a separate preamplifier and amplifier. The receiver is a combination of the preamplifier, amplifier and a radio tuner and still operates in the same fashion as separate components, albeit in one package. An integrated amplifier includes the preamplifier and amplifier in one unit, without a radio tuner.


A separate component system is the preference of many discerning audiophiles who want the highest performance system and best sound. Separate preamplifiers and amplifiers also allow for more flexibility in choosing specific components, upgrading the system and repairing a problematic component. For simpler, less expensive systems a receiver will function just fine.


In a simple system configuration, all your audio sources will be connected to the preamp with audio cable (digital or analog). The preamp is connected via RCA cables to the amplifier, and the amplifier is connected with speaker cable to the left and right speakers.