Audio power amplifier

This was made possible by his invention of the first practical amplifying electrical component, the triode vacuum tube (or "valve" in British English) in 1907.

The triode was a three-terminal device with a control grid that can modulate the flow of electrons from the filament to the plate.

JVC, Pioneer Corporation, Sony and Toshiba also began manufacturing amplifiers with power MOSFETs in 1974.

Key design parameters for audio power amplifiers are frequency response, gain, noise, and distortion.

During the 1970s, tube amps were increasingly replaced with transistor-based amplifiers, which were lighter in weight, more reliable, and lower maintenance.

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.

Since modern digital devices, including CD and DVD players, radio receivers and tape decks already provide a "flat" signal at line level, the preamp is not needed other than as a volume control and source selector.

[14] TIM did not appear at steady state sine tone measurements, helping to hide it from design engineers prior to 1970.

Problems with TIM distortion stem from reduced open loop frequency response of solid-state amplifiers.

Further works of Otala and other authors found the solution for TIM distortion, including increasing slew rate, decreasing preamp frequency bandwidth, and the insertion of a lag compensation circuit in the input stage of the amplifier.

[15][16][17] In high-quality modern amplifiers the open loop response is at least 20 kHz, canceling TIM distortion.

Most consumer electronics sound products, such as TVs, boom boxes, home cinema sound systems, Casio and Yamaha electronic keyboards, "combo" guitar amps and car stereos have power amplifiers integrated inside the chassis of the main product.

Audio stereo power amplifier made by McIntosh
The internal view of a Mission Cyrus One hi-fi integrated audio amplifier (1984) [ 1 ]
De Forest's prototype audio amplifier of 1914
McIntosh MC240 from 1961, with exposed vacuum tubes
Five rack-mounted audio power amplifiers used in a sound reinforcement system
A micro audio amplifier for boosting the output of line level sources to headphones or small speakers. Edge length 4 cm, mass 16 g , power output about 100 mW into a 32 Ω load.
Pyle two-channel power amplifier
Rear panel of a medium-sized sound reinforcement system located at one side of the stage at a pop concert. The setup includes the mixing console for the sound engineer (standing behind) and the power amplifiers which are partly stacked in a 19-inch rack on the right.