Editing Audio power amplifier (section)

== Design parameters ==
{{unreferenced section|date=November 2019}}
[[File:Professional PA power amps from Crest Audio and QSC with control modules in rack.jpg|thumb|upright=0.8|Five rack-mounted audio power amplifiers used in a [[sound reinforcement system]]]]
Key design parameters for audio power amplifiers are [[frequency response]], [[gain (electronics)|gain]], [[noise (electronics)|noise]], and [[distortion]]. These are interdependent; increasing gain often leads to undesirable increases in noise and distortion. While [[negative feedback]] actually reduces the gain, it also reduces distortion. Most audio amplifiers are linear amplifiers operating in [[Power amplifier classes|class AB]].

Until the 1970s, most amplifiers used [[vacuum tube]]s. During the 1970s, tube amps were increasingly replaced with [[transistor]]-based amplifiers, which were lighter in weight, more reliable, and lower maintenance. Nevertheless, tube preamplifiers are still sold in [[niche market]]s, such as with home [[hi-fi]] enthusiasts, [[audio engineer]]s and [[music producer]]s (who use tube preamplifiers in studio recordings to "warm up" microphone signals) and electric guitarists, electric bassists and [[Hammond organ]] players, of whom a minority continue to use tube preamps, tube power amps and tube [[effects unit]]s. While hi-fi enthusiasts and audio engineers doing live sound or monitoring tracks in the studio typically seek out amplifiers with the lowest distortion, electric instrument players in genres such as [[blues]], [[rock music]] and [[heavy metal music]], among others, use tube amplifiers because they like the natural overdrive that tube amps produce when pushed hard.

The [[class-D amplifier]], which is much more efficient than class-AB amplifiers, is now widely used in [[consumer electronics]] audio products, [[bass amplifier]]s and [[sound reinforcement system]] gear, as class-D amplifiers are much lighter in weight and produce much less heat, but may introduce some noise.