Tone control is a type of equalization used to make specific pitches or "

frequencies Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

" in an

audio Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to: Sound *Audio signal, an electrical representation of sound *Audio frequency, a frequency in the audio spectrum *Digital audio, representation of sound ...

signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...

softer or louder. It allows a listener to adjust the tone of the sound produced by an

audio system Sound recording and reproduction is the electrical, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording te ...

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 An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is a type of electrical ...

that consists of a network of

filters Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...

which modify the signal before it is fed to

speakers Speaker may refer to: Society and politics * Speaker (politics), the presiding officer in a legislative assembly * Public speaker, one who gives a speech or lecture * A person producing speech: the producer of a given utterance, especially: ** In ...

headphones Headphones are a pair of small loudspeaker drivers worn on or around the head over a user's ears. They are electroacoustic transducers, which convert an electrical signal to a corresponding sound. Headphones let a single user listen to an au ...

or recording devices by way of an

amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost the v ...

. Tone controls are found on many sound systems:

radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmit ...

portable music player A portable audio player is a personal mobile device that allows the user to listen to recorded audio while mobile. Sometimes a distinction is made between a ''portable'' player, battery-powered and with one or more small loudspeakers, and a ''pers ...

boomboxes A boombox is a transistorized portable music player featuring one or two cassette tape recorder/players and AM/FM radio, generally with a carrying handle. Beginning in the mid 1980s, a CD player was often included. Sound is delivered through ...

public address system A public address system (or PA system) is an electronic system comprising microphones, amplifiers, loudspeakers, and related equipment. It increases the apparent volume (loudness) of a human voice, musical instrument, or other acoustic sound sou ...

s, and musical instrument amplifiers.

Uses

Tone control allows listeners to adjust sound to their liking. It also enables them to compensate for recording deficiencies, hearing impairments, room

acoustics Acoustics is a branch of physics that deals with the study of mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician ...

or shortcomings with playback equipment. For example, older people with hearing problems may want to increase the loudness of high pitch sounds they have difficulty hearing. Tone control is also used to adjust an audio signal during recording. For instance, if the acoustics of the recording site cause it to absorb some frequencies more than others, tone control can be used to amplify or "boost" the frequencies the room dampens.

Types

In their most basic form, tone control circuits

attenuate In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable a ...

the high or low

of the signal. This is called

treble Treble may refer to: In music: *Treble (sound), tones of high frequency or range, the counterpart of bass *Treble voice, a choirboy or choirgirl singing in the soprano range *Treble (musical group), a three-piece girl group from the Netherlands *T ...

or bass "cut". The simplest tone control circuits are

passive circuit Passivity is a property of engineering systems, most commonly encountered in analog electronics and control systems. Typically, analog designers use ''passivity'' to refer to incrementally passive components and systems, which are incapable of p ...

s which utilize only

resistors A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active el ...

and

capacitors A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of a ...

inductors An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a ...

. They rely on the property of

capacitive reactance In electrical circuits, reactance is the opposition presented to alternating current by inductance or capacitance. Greater reactance gives smaller current for the same applied voltage. Reactance is similar to resistance in this respect, but doe ...

inductive reactance In electrical circuits, reactance is the opposition presented to alternating current by inductance or capacitance. Greater reactance gives smaller current for the same applied voltage. Reactance is similar to resistance in this respect, but doe ...

to inhibit or enhance an AC signal, in a frequency-dependent manner. Active tone controls may also amplify or "boost" certain frequencies. More elaborate tone control circuits can boost or attenuate the middle range of frequencies. The simplest tone control is a single knob that when turned in one direction enhances treble frequencies and the other direction enhances bass frequencies. This was the first type of tone control, typically found on radios and

record player A phonograph, in its later forms also called a gramophone (as a trademark since 1887, as a generic name in the UK since 1910) or since the 1940s called a record player, or more recently a turntable, is a device for the mechanical and analogu ...

s from the 1930s to the 1970s.

Graphic equalizer Equalization, or simply EQ, in sound recording and reproduction is the process of adjusting the volume of different frequency bands within an audio signal. The circuit or equipment used to achieve this is called an equalizer. Most hi-fi eq ...

s used for tone control provide independent elevation or attenuation of individual bands of frequencies. Wide frequency range graphic equalizers of high resolution can provide elevation or attenuation in 1/3 octave bands spanning from approximately 30 Hz to 18 kHz.

Parametric equalizer Equalization, or simply EQ, in sound recording and reproduction is the process of adjusting the volume of different frequency bands within an audio signal. The circuit or equipment used to achieve this is called an equalizer. Most hi-fi eq ...

s can control not only the amount of boost and cut but also the specific frequency at which the boost and cut takes place and the range of frequencies (

bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...

) affected. Elaborate circuits may also use amplifiers. The most modern analog units use

operational amplifiers An operational amplifier (often op amp or opamp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. In this configuration, an op amp produces an output potential (relative to c ...

, resistors and capacitors, abandoning inductors because of their size and sensitivity to ubiquitous

electromagnetic interference Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electros ...

. Historically, tone control was achieved via

analog electronics Analogue electronics ( en-US, analog electronics) are electronic systems with a continuously variable signal, in contrast to digital electronics where signals usually take only two levels. The term "analogue" describes the proportional relati ...

, and most tone control circuits produced today still use the analog process. Nonetheless,

digital Digital usually refers to something using discrete digits, often binary digits. Technology and computing Hardware *Digital electronics, electronic circuits which operate using digital signals **Digital camera, which captures and stores digital i ...

approaches are increasingly being implemented through the use of

digital signal processing Digital signal processing (DSP) is the use of digital processing, such as by computers or more specialized digital signal processors, to perform a wide variety of signal processing operations. The digital signals processed in this manner are ...

External links

{{Commonscat, Tone control
The James-Baxandall Passive Tone-Control NetworkNegative-Feedback Tone Control - Independent Variation of Bass and Treble Without Switches by P. J. Baxandall -pdfTone control for DJs
NB. The above mentioned file should now be downloaded fro

Also, an article referenced by it entitled "Simple Tone Control Circuit: Bass and Treble, Cut and Lift, by E.J.James" may be downloaded from there as well.

Analog circuits Tone, EQ and filter

Uses

Types

See also

External links