Douglas Self | |
|---|---|
| Nationality | British |
| Alma mater | Cambridge University |
| Known for | Author, Electronic Engineer |
Douglas Self is a British electronics engineer and author with a particular interest in audio. He received a first class honours degree in engineering from Cambridge University, and then studied psychoacoustics at Sussex University. [1] He is the author of six books on audio electronics, published by Focal Press. [2] He has also contributed many articles to Wireless World magazine, some of which were compiled into a book along with articles by Peter Baxandall. [3] [4] [5]
He is a member of the Audio Engineering Society and has taken out a number of audio-related patents, including for a "crossover displacement circuit". [1] [6]
He has worked with several major companies, including Cambridge Audio, TAG-McLaren Audio, and Soundcraft Electronics. [7] Circuit Cellar website described him as a 'renowned audio specialist' when discussing a design he created for Elektor magazine. [8] He developed the concept, accompanied with a practical design, of a "blameless" amplifier in which all the main sources of distortion for a pure Class B amplifier are reduced to negligible levels, to challenge the notion that such a topology is not suitable for Hi-Fi audio. [3]
Self's books have been well received. His Audio Power Amplifier Design Handbook was recommended by Walt Jung and described as "famous" by audio website hifisonix. [9] [10] The second edition of his Small Signal Audio Design received a very positive review in Sound on Sound magazine. [11]
An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the power of a signal. It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its gain: the ratio of output voltage, current, or power to input. An amplifier is a circuit that has a power gain greater than one.
An effects unit or effects pedal is an electronic device that alters the sound of a musical instrument or other audio source through audio signal processing.
A loudspeaker is one type of electroacoustic transducer, that is, a device that converts an electrical audio signal into a corresponding sound. A speaker system, also often simply referred to as a "speaker" or "loudspeaker", comprises one or more such speaker drivers, an enclosure, and electrical connections possibly including a crossover network. The speaker driver can be viewed as a linear motor attached to a diaphragm which couples that motor's movement to motion of air, that is, sound. An audio signal, typically from a microphone, recording, or radio broadcast, is amplified electronically to a power level capable of driving that motor in order to reproduce the sound corresponding to the original unamplified electronic signal. This is thus the opposite function to the microphone; indeed the dynamic speaker driver, by far the most common type, is a linear motor in the same basic configuration as the dynamic microphone which uses such a motor in reverse, as a generator.
An audio power amplifier is an electronic amplifier that amplifies low-power electronic audio signals, such as the signal from a radio receiver or an electric guitar pickup, to a level that is high enough for driving loudspeakers or headphones. Audio power amplifiers are found in all manner of sound systems including sound reinforcement, public address and home audio systems and musical instrument amplifiers like guitar amplifiers. It is the final electronic stage in a typical audio playback chain before the signal is sent to the loudspeakers.
Audio crossovers are a type of electronic filter circuitry that splits an audio signal into two or more frequency ranges, so that the signals can be sent to loudspeaker drivers that are designed to operate within different frequency ranges. The crossover filters can be either active or passive. They are often described as two-way or three-way, which indicate, respectively, that the crossover splits a given signal into two frequency ranges or three frequency ranges. Crossovers are used in loudspeaker cabinets, power amplifiers in consumer electronics and pro audio and musical instrument amplifier products. For the latter two markets, crossovers are used in bass amplifiers, keyboard amplifiers, bass and keyboard speaker enclosures and sound reinforcement system equipment.
Audio system measurements are a means of quantifying system performance. These measurements are made for several purposes. Designers take measurements so that they can specify the performance of a piece of equipment. Maintenance engineers make them to ensure equipment is still working to specification, or to ensure that the cumulative defects of an audio path are within limits considered acceptable. Audio system measurements often accommodate psychoacoustic principles to measure the system in a way that relates to human hearing.
Audio equipment refers to devices that reproduce, record, or process sound. This includes microphones, radio receivers, AV receivers, CD players, tape recorders, amplifiers, mixing consoles, effects units, headphones, and speakers.
In electronics, a limiter is a circuit that allows signals below a specified input power or level to pass unaffected while attenuating (lowering) the peaks of stronger signals that exceed this threshold. Limiting is a type of dynamic range compression. Clipping is an extreme version of limiting.
A push–pull amplifier is a type of electronic circuit that uses a pair of active devices that alternately supply current to, or absorb current from, a connected load. This kind of amplifier can enhance both the load capacity and switching speed.
Tone control is a type of equalization used to make specific pitches or "frequencies" in an audio signal softer or louder. It allows a listener to adjust the tone of the sound produced by an audio system to their liking, for example to compensate for inadequate bass response of loudspeakers or earphones, tonal qualities of the room, or hearing impairment. A tone control circuit is an electronic circuit that consists of a network of filters which modify the signal before it is fed to speakers, headphones or recording devices by way of an amplifier. Tone controls are found on many sound systems: radios, portable music players, boomboxes, public address systems, and musical instrument amplifiers.
Powered speakers, also known as self-powered speakers and active speakers, are loudspeakers that have built-in amplifiers. Powered speakers are used in a range of settings, including in sound reinforcement systems, both for the main speakers facing the audience and the monitor speakers facing the performers; by DJs performing at dance events and raves; in private homes as part of hi-fi or home cinema audio systems and as computer speakers. They can be connected directly to a mixing console or other low-level audio signal source without the need for an external amplifier. Some active speakers designed for sound reinforcement system use have an onboard mixing console and microphone preamplifier, which enables microphones to be connected directly to the speaker.
Clipping is a form of waveform distortion that occurs when an amplifier is overdriven and attempts to deliver an output voltage or current beyond its maximum capability. Driving an amplifier into clipping may cause it to output power in excess of its power rating.
In electronics, motorboating is a type of low frequency parasitic oscillation that sometimes occurs in audio and radio equipment and often manifests itself as a sound similar to an idling motorboat engine, a "put-put-put", in audio output from speakers or earphones. It is a problem encountered particularly in radio transceivers and older vacuum tube audio systems, guitar amplifiers, PA systems and is caused by some type of unwanted feedback in the circuit. The amplifying devices in audio and radio equipment are vulnerable to a variety of feedback problems, which can cause distinctive noise in the output. The term motorboating is applied to oscillations whose frequency is below the range of hearing, from 1 to 10 hertz, so the individual oscillations are heard as pulses. Sometimes the oscillations can even be seen visually as the woofer cones in speakers slowly moving in and out.
Distortion and overdrive are forms of audio signal processing used to alter the sound of amplified electric musical instruments, usually by increasing their gain, producing a "fuzzy", "growling", or "gritty" tone. Distortion is most commonly used with the electric guitar, but may also be used with other electric instruments such as electric bass, electric piano, and Hammond organ. Guitarists playing electric blues originally obtained an overdriven sound by turning up their vacuum tube-powered guitar amplifiers to high volumes, which caused the signal to distort. While overdriven tube amps are still used to obtain overdrive, especially in genres like blues and rockabilly, a number of other ways to produce distortion have been developed since the 1960s, such as distortion effect pedals. The growling tone of a distorted electric guitar is a key part of many genres, including blues and many rock music genres, notably hard rock, punk rock, hardcore punk, acid rock, and heavy metal music, while the use of distorted bass has been essential in a genre of hip hop music and alternative hip hop known as "SoundCloud rap".
Nelson Pass is a designer of audio amplifiers. Pass is vocal that listening tests remain valuable and that electrical measurements alone do not fully characterize the sound of an amplifier. Pass holds at least seven U.S. patents related to audio circuits.
Peter J. Baxandall 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.
Tube sound is the characteristic sound associated with a vacuum tube amplifier, a vacuum tube-based audio amplifier. At first, the concept of tube sound did not exist, because practically all electronic amplification of audio signals was done with vacuum tubes and other comparable methods were not known or used. After introduction of solid state amplifiers, tube sound appeared as the logical complement of transistor sound, which had some negative connotations due to crossover distortion in early transistor amplifiers. However, solid state amplifiers have been developed to be flawless and the sound is later regarded neutral compared to tube amplifiers. Thus the tube sound now means 'euphonic distortion.' The audible significance of tube amplification on audio signals is a subject of continuing debate among audio enthusiasts.
Class XD is a proprietary and patented amplifier technology developed in-house by Cambridge Audio.
In electronics, power amplifier classes are letter symbols applied to different power amplifier types. The class gives a broad indication of an amplifier's characteristics and performance. The classes are related to the time period that the active amplifier device is passing current, expressed as a fraction of the period of a signal waveform applied to the input. A class A amplifier is conducting through all the period of the signal; Class B only for one-half the input period, class C for much less than half the input period. A Class D amplifier operates its output device in a switching manner; the fraction of the time that the device is conducting is adjusted so a pulse-width modulation output is obtained from the stage.
The NE5532, also sold as SA5532, SE5532 and NG5532 is a dual monolithic, bipolar, internally compensated operational amplifier for audio applications introduced by Signetics in 1979. The 5532 and the contemporary TL072 were the first operational amplifiers that outperformed discrete class A circuits in professional audio applications. Due to low noise and very low distortion, the 5532 became the industry standard for professional audio. According to Douglas Self, "there is probably no music on the planet that has not passed through a hundred or more 5532s on its way to the consumer". The performance of the 5532 remained best in class for almost thirty years, until the introduction of the LM4562 in 2007. As of 2021, the 5532 remains in mass production as a generic product.
As is often the case with articles on audio subjects, Douglas Self's recent series on amplifier distortion caused a great deal of interest worldwide.
Then there’s Douglas Self’s innovative crossover displacement circuit, for which he was awarded British Patent GB2424137.
...I can recommend the book as a general source of audio power amplifier knowledge
In 1996, Douglas Self published his now famous 'Audio Power Amplifier Design Handbook', in which he described the 8 key distortion mechanisms in audio power amplifiers
excellent technical reference book... if you have the slightest interest in audio circuit design this book has to be considered an essential reference. Very highly recommended.
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