• A preamplifier and a power amp are often combined in one unit.Jupiterimages/Photos.com/Getty Images
  
  A preamplifier does not merely boost the volume of your audio signal before it reaches a main amplifier, as the term misleadingly implies. If you a play a musical instrument as part of a live set up, produce music at home using audio hardware or are an AV enthusiast who likes to get the best sonic experience from your equipment, your preamp plays a vital role in preparing your audio signal for amplification and a very different one to your main amplifier.
  
  

Preamplifier

• A standalone preamplifier should be the final component in the chain before an audio signal is routed to a main, or power, amplifier. If you're playing guitar or another musical instrument, it should be connected to the output of any other effects units you're using to treat your signal before amplification. If you're using a preamp at home with AV equipment, the audio signal should be routed from the source unit, a CD player or a turntable for example, to the preamp and then on to the main amplifier. A preamplifier calibrates the audio signal from a low-level source input such as a microphone, pick-up or turntable and prepares it to processed by a traditional amplifier. It also adds controls such as tone and equalization or acts as a switching device between various source inputs.
  
  

Amplifier

• An amplifier, or power amplifier, takes the signal produced by the preamplifier and translates it to a signal that can be relayed through a set of speakers or headphones. A main amplifier increases the power and sound of the signal provided by the preamplifier before the final result is heard.
  
  

Combo Unit

• Many amplifiers, whether used by musicians or in the home, contain a preamplifier and a power amplifier within the same unit, which is why a distinction is often not made between the two.