Tone control circuits
Encyclopedia
Tone control is a type of equalization
used to make specific pitches or "frequencies
" in an audio
signal
softer or louder. 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 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.
or bass
"cut". The simplest tone control circuits are passive circuits which utilize only resistors and capacitors or inductors. They rely on the property of capacitive reactance or inductive reactance 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.
Graphic equalizers used for tone control provide elevation or attenuation in 1/3 octave bands spanning from approximately 30 Hz to 18 kHz.
Parametric equalizers 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) affected.
Elaborate circuits may also use amplifiers. The most modern analog units use operational amplifiers, resistors and capacitors, abandoning inductors because of their size and sensitivity to ubiquitous electromagnetic interference
.
Historically, tone control was achieved via analog electronics, and most tone control circuits produced today still use the analog process. Nonetheless, digital
approaches are increasingly being implemented through the use of digital signal processing
.
NB. The above mentioned file should now be downloaded from http://www.thermionic.info/
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.
Equalization (audio)
Equalization is the process commonly used in sound recording and reproduction to alter the frequency response of an audio system using linear filters. Most hi-fi equipment uses relatively simple filters to make bass and treble adjustments. Graphic and parametric equalizers have much more...
used to make specific pitches or "frequencies
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
" in an audio
Sound recording and reproduction
Sound recording and reproduction is an electrical or mechanical inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording...
signal
Signal (electrical engineering)
In the fields of communications, signal processing, and in electrical engineering more generally, a signal is any time-varying or spatial-varying quantity....
softer or louder. A tone control circuit is an electronic circuit
Electrical network
An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...
that consists of a network of filters which modify the signal before it is fed to speakers
Loudspeaker
A loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...
, headphones
Headphones
Headphones are a pair of small loudspeakers, or less commonly a single speaker, held close to a user's ears and connected to a signal source such as an audio amplifier, radio, CD player or portable Media Player. They are also known as stereophones, headsets or, colloquially, cans. The in-ear...
or recording devices by way of an amplifier
Electronic amplifier
An electronic amplifier is a device for increasing the power of a signal.It does this by taking energy from a power supply and controlling the output to match the input signal shape but with a larger amplitude...
.
Uses
Tone control allows listeners to adjust sound to their liking. It also enables them to compensate for recording deficiencies, hearing impairments, room acoustics 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
Acoustics
Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of 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 the high or low frequencies of the signal. This is called trebleLow-pass filter
A low-pass filter is an electronic filter that passes low-frequency signals but attenuates signals with frequencies higher than the cutoff frequency. The actual amount of attenuation for each frequency varies from filter to filter. It is sometimes called a high-cut filter, or treble cut filter...
or bass
High-pass filter
A high-pass filter is a device that passes high frequencies and attenuates frequencies lower than its cutoff frequency. A high-pass filter is usually modeled as a linear time-invariant system...
"cut". The simplest tone control circuits are passive circuits which utilize only resistors and capacitors or inductors. They rely on the property of capacitive reactance or inductive reactance to inhibit or enhance an AC
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
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.
Graphic equalizers used for tone control provide elevation or attenuation in 1/3 octave bands spanning from approximately 30 Hz to 18 kHz.
Parametric equalizers 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) affected.
Elaborate circuits may also use amplifiers. The most modern analog units use operational amplifiers, resistors and capacitors, abandoning inductors because of their size and sensitivity to ubiquitous electromagnetic interference
Electromagnetic interference
Electromagnetic interference is disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of the circuit...
.
Historically, tone control was achieved via analog electronics, and most tone control circuits produced today still use the analog process. Nonetheless, digital
Digital circuit
Digital electronics represent signals by discrete bands of analog levels, rather than by a continuous range. All levels within a band represent the same signal state...
approaches are increasingly being implemented through the use of digital signal processing
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...
.
See also
- Audio amplifierAudio amplifierAn audio amplifier is an electronic amplifier that amplifies low-power audio signals to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain.The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification,...
- Electronic filterElectronic filterElectronic filters are electronic circuits which perform signal processing functions, specifically to remove unwanted frequency components from the signal, to enhance wanted ones, or both...
- Audio crossoverAudio crossoverAudio crossovers are a class of electronic filter used in audio applications. Most individual loudspeaker drivers are incapable of covering the entire audio spectrum from low frequencies to high frequencies with acceptable relative volume and lack of distortion so most hi-fi speaker systems use a...
- Equalization (audio)Equalization (audio)Equalization is the process commonly used in sound recording and reproduction to alter the frequency response of an audio system using linear filters. Most hi-fi equipment uses relatively simple filters to make bass and treble adjustments. Graphic and parametric equalizers have much more...
External links
- The Peter-James-Baxandall Passive Tone-Control Network
- Amplifiers and tone controls
- Audio tone controls
- Negative-Feedback Tone Control - Independent Variation of Bass and Treble Without Switches by P. J. Baxandall -pdf
NB. The above mentioned file should now be downloaded from http://www.thermionic.info/
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.