page_title: Valve audio amplifier
section_title: Tube hi-fi in the 1960s
hierarchical_section_title: Valve audio amplifier / Amplifiers for sound reproduction / Tube hi-fi in the 1960s
caption_attribution_description: English: Schematic of a push-pull tube poweramplifier for audio
context_page_description: A valve audio amplifier or vacuum tube audio amplifier is a valve amplifier used for sound reinforcement, sound recording and reproduction.
  Until the invention of solid state devices such as the transistor, all electronic amplification was produced by valve amplifiers. While solid-state devices prevail in most audio amplifiers today, valve audio amplifiers are still used where their audible characteristics are considered pleasing, for example in music performance or music reproduction.
context_section_description: Valve amplification peaked as the mainstream technology during the 1960s and 70s, with device and circuits being highly developed. There have been only minor refinements since then.
  The last generation of power tubes, typified by KT66, EL34 and KT88, represent the pinnacle of the technology and of production quality. Valve amplifiers produced since that time usually use one of these tubes, which have remained in continuous production (apart from KT66) ever since. Output power was typically 20 watts, exceptionally 35W.
  Small signal valves overwhelmingly changed from octal base tubes, notably the audio tube of choice, the 6SN7 family, to the smaller and cheaper noval base ECC81, ECC82, ECC83 (UK, in the US known as 12AX7,12AT7, etc.). The lower-power noval base EL84 power pentode was widely used in less expensive 10-watt ultralinear power amplifiers, still of high fidelity.
  Commercial tube manufacturers developed designs based on their own products, most notably the Mullard 5-10 circuit. This design and the Williamson were widely implemented and imitated, with or without crediting the originator.
caption: Conceptual diagram of a poweramplifier with a split-load phase inverter and push-pull EL34 pentodes endstage
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