Peter Baxandall

{{Infobox person | honorific_prefix = | name = Peter James Baxandall | honorific_suffix = | image = Peter_Baxandall.png | image_size = | alt = | caption = | native_name = | native_name_lang = | birth_name = | birth_date = {{Birth date|df=y|1921|8|11}} | birth_place = [[Kingston upon Thames]] | death_date = {{Death date and age|df=y|1995|9|8|1921|8|11}} | death_place = [[Malvern, Worcestershire]] | resting_place = | resting_place_coordinates = | education = | spouse = | parents = | children = | module = {{Infobox engineering career | discipline = [[Audio engineer]]ing<br />[[Electronic engineering]] | institutions = [[King's College School]] | practice_name = | employer = | significant_projects = Baxandall [[tone control circuit]] | significant_design = | significant_advance = | significant_awards = [[Audio Engineering Society|AES Silver Medal Award]], 1993 }} | signature = | signature_alt = | website = }}

'''Peter James Baxandall''' (August 11, 1921, [[Kingston upon Thames]], [[Surrey]] – September 8, 1995, [[Malvern, Worcestershire|Malvern]], [[Worcestershire]]) was an English [[audio engineer]] and [[electronics engineer]] and a pioneer of the use of analog electronics in audio. He is probably best known for what is now called the Baxandall [[tone control circuit]], first published in a paper in ''[[Wireless World]]''.

==Biography== Baxandall attended [[King's College School]] in London, then got his BSc in electrical engineering at [[Bute Building|Cardiff Technical College]] (1942). He was a radio instructor for the [[Fleet Air Arm]] for two years, and then worked for the [[Telecommunications Research Establishment]] (at the Circuit Research Division headed by [[Frederic Calland Williams]]), later renamed and merged to form the [[Royal Signals and Radar Establishment]], until his retirement in 1971. After retiring he worked as a consultant on various audio projects including loudspeakers, tape duplication, and microphone calibration. During this time he continued to publish, including a "seminal chapter" on [[electrostatic loudspeaker]]s. The [[Audio Engineering Society]] made him a Fellow in 1980, and in 1993 awarded him with a Silver Medal for his contributions to the field.<ref name="fincham">{{cite journal|last=Fincham|first=Laurie|year=|title=In Memoriam: Peter Baxandall|journal=Journal of the Audio Engineering Society|publisher=[[Audio Engineering Society]]|volume=44|issue=9|page=796|url=https://web.archive.org/web/20191016085202/https://aes.org/aeshc/jaes.obit/JAES_V44_9_PG796.pdf|date=September 1996}}</ref>

==Baxandall tone control circuit== Baxandall's bass and treble control circuit, when made public in ''Wireless World'' (1952)<ref>{{Cite journal |last=Baxandall |first=P. J. |date=October 1952 |title=Negative-feedback tone control |url=https://archive.org/details/sim_wireless-world_1952-10_58_10/page/n119/mode/2up |journal=Wireless World |pages=402-405}}</ref>, "swept all others before it".<ref name="Self2010"/> An early version of the design had already won him an award in 1950 (a $25 watch) at the British Sound Recording Association, a predecessor of the [[Audio Engineering Society]]. The design is now employed in millions of hi-fi systems (Baxandall received no royalties for his work).<ref name="fincham"/>

It exists in several versions—Baxandall's original had two capacitors per potentiometer, but it is possible to use only one at either the treble or bass potentiometers, or both.<ref name="Self2010">{{cite book|last=Self|first=Douglas|title=Small Signal Audio Design|url=https://books.google.com/books?id=PvKPEFu2PVkC&pg=PA259|accessdate=28 May 2012|year=2010|publisher=Focal|isbn=9780240521770|pages=259–68}}</ref> In audio literature, “Baxandall” is sometimes used generically for bass–treble tone controls, even when the circuit omits negative feedback and more closely follows the earlier passive design published by E. J. James.<ref name="James1949">{{cite journal |last=James |first=E. J. |title=Simple Tone Control Circuit: Bass and Treble, Cut and Lift |journal=Wireless World |date=February 1949 |pages=48–50}}</ref><ref name="J.Dailey2011">{{cite book|last1=J.|first1=Denton Dailey|last2=Dailey|first2=Denton J.|title=Electronics for Guitarists|url=https://books.google.com/books?id=PPg5_lPQJyMC&pg=PA47|accessdate=28 May 2012|year=2011|publisher=Springer|isbn=9781441995353|pages=47–49}}</ref><ref>{{cite news|title=Ampeg GVT5-110, GVT15H, and GVT52-112|last=Thompson|first=Art|date=December 2011|work=[[Guitar Player]]|pages=96–102}}</ref> == Class D definition == In a 1959 paper on transistor wave oscillators, Baxandall proposed the term “[[Class-D amplifier|class-D]]” to describe a mode of switching operation in which active devices conduct current only when the voltage across them is low. His analysis treated the output devices as switches rather than linear. Although discussed in the context of oscillators rather than audio power amplifiers, the terminology and operating principles later became associated with class-D power amplification. <ref>{{cite journal |last=Baxandall |first=P. J. |title=Transistor sine-wave oscillators |journal=Proceedings of the IEE |volume=106 |issue=2 |pages=748-758 |year= |doi=10.1049/pi-b-2.1959.0141|date=February 1960}}</ref> == References == {{reflist}}

==External links== *[http://www.learnabout-electronics.org/Downloads/NegativeFeedbackTone.pdf Baxandall, "Negative Feedback Tone Control"] (article from ''Wireless World'', October 1952]

{{DEFAULTSORT:Baxandall, Peter}} [[Category:English audio engineers]] [[Category:1921 births]] [[Category:1995 deaths]] [[Category:Signal processing filter]] [[Category:Tone, EQ and filter]]