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Topic: Voltage controlled filter

	Voltage-controlled filter - Wikipedia, the free encyclopedia
		A voltage-controlled filter (VCF) is a signal processing device in an analog synthesizer positioned after the oscillator.
		A VCF is an example of an active non-linear filter: however, if its control voltage is kept constant, it will behave as a linear filter.
		A VCF allows its cutoff frequency and Q factor to be continuously varied; it usually gives a lowpass response, but may also be switchable to allow highpass, bandpass or even notch responses.
	en.wikipedia.org /wiki/Voltage-controlled_filter (170 words)

	Voltage-controlled filter - Patent 4039980
		It is convenient in a voltage curcuit (not shown) provided for generating the control voltage to indicate the cut-off frequency by a logarithmic indication and produce the control voltage logarithmically relative to the cut-off frequency, because this arrangement affords a wider range of variation in the cut-off frequency.
		Accordingly, the base voltage of the npn transistors Tr.sub.4 and Tr.sub.5 are controlled by the control voltage applied to the terminal VC, and a sum of a potential of the resistor R.sub.5 to ground and the base-emitter voltage of the transistor Tr.sub.6 becomes the base voltage of the transistors Tr.sub.4 and Tr.sub.5.
		The control voltage applied to the input terminal VQ is applied to the base of a transistor Tr.sub.10 and current corresponding to the control voltage flows through the emitter and the collector of the transistor Tr.sub.10.
	www.freepatentsonline.com /4039980.html (3592 words)

	Art's Theremin Page: Infrared Optical Theremin Technical Disclosure
		The output from the voltage controlled filter is connected to the input of the voltage controlled amplifier (K).
		The voltage controlled amplifier controls the amplitude of the waveform from the voltage controlled filter in accordance with the value of the voltage present at the output of the volume circuit difference amplifier.
		An increase of voltage causes a proportional increase of voltage controlled amplifier gain, thus, as the hand moves toward the volume emitter/detector pair, a corresponding increase results in the amplitude of the waveform at the output of the voltage controlled amplifier.
	home.att.net /~theremin1/irtheremin.htm (1837 words)

	[No title]
		It is an oscillator whose pitch (or frequency) is controlled by an input voltage.
		Voltage is an electric charge, or potential, between two points, one being of higher relative voltage than the other is. A 1.5-volt battery has 1.5 volts of differential between the positive and negative end, for example.
		It is a filter circuit whose value is controlled by a voltage applied to it.
	www.nathanspage.com /wftd/wftd_v.html (1517 words)

	Wind Synthesizer -- Up Close (Site not responding. Last check: 2007-10-08)
		The input signals from the controller are 1) "CV", the one-octave per volt main control voltage and 2) "E", the wind or breath envelope control voltage.
		The frequency-control input of the voltage controlled oscillator (VCO) is connected (or "patched") to CV, producing musical pitches corresponding to the fingering of the controller.
		The amplitude-control input of the voltage controlled amplifier (VCA) is patched to E, producing a signal amplitude -- or musical volume -- proportional to the blowing force.
	home.earthlink.net /~ijfritz/sy_close.htm (865 words)

	TLN-442 Voltage Controlled Lowpass Filter (Site not responding. Last check: 2007-10-08)
		The filter frequency can be set using a panel mounted pot, a "one volt per octave" external control voltage, or via two external FM inputs with attenuators (one reversing).
		Filter resonance can be set using a panel mounted pot or an external control voltage with a reversing attenuator.
		A four pole low pass filter built with a CEM 3320 was used in the Sequential Circuits Prophet Five (rev. 3) and Pro One synthesizers.
	www.tellun.com /motm/diy/tln442/TLN-442.html (342 words)

	[No title] (Site not responding. Last check: 2007-10-08)
		Control voltage dropped across R38 is picked off at the wiper and current is fed through R28 to the base of Q3.
		This causes the pole frequency of the filter circuit to go up passing higher har- monics of the signal being fed in to the output.
		VOLTAGE CONTROLLED AMPLIFIER (VCA)-(See figure 5) The input signal to the Voltage Controlled Amplifier is fed into R24 and dropped on R23.
	www.musicfromouterspace.com /analogsynth/WP20/WP20_PG15.html (339 words)

	PAiA: 9730 Voltage Controlled Filter
		Control Voltage scaling is 1V/oct. Resonance ("Q") has both a front panel knob and Control Voltage input.
		Signal and control flow are normalized for use as a single filter - the A filter LP ouput internally connects to the B filter input so that a patch cord is not required for this very useful configuration.
		Filter sweeps are typical of the kinds of sounds that are rare in nature and in the early days of synthesis these "new" sounds were used so often that they have become a little trite when not worked in as integral part of a composition.
	www.paia.com /9730.htm (839 words)

	Voltage-controlled filter - the free encyclopedia (Site not responding. Last check: 2007-10-08)
		A voltage-controlled filter (VCF) is a signal processing device in an
		A VCF is an example of an active
		non-linear filter: however, if its control voltage is kept constant, it will behave as a
	www.world-knowledge-encyclopedia.com /?t=VCF (115 words)

	Synth Glossary
		VCA : Voltage Controlled Amplifier - a device that controls the amplitude of a signal in proportion to the voltage applied to it.
		VCF : Voltage Controlled Filter - a device that removes unwanted frequencies from a signal, dependent on the voltage applied to it.
		VCO : Voltage Controlled Oscillator - A device generating a periodic waveform whose frequency is proportional to the voltage applied.
	www.fortunecity.com /emachines/e11/86/synthglos2.html (1042 words)

	Roland MC-8 Microcomposer - Wikipedia, the free encyclopedia
		The Roland MC-8 MicroComposer was introduced in 1977 at a price of around $8000 as the world's first digital microprocessor driven, VC (Voltage Control) unit, (a pre-MIDI sequencing method used for electronic music).
		The MicroComposer could precisely adjust multiple sound producing and effects elements of a synthesizer, such as the VCO (Voltage Controlled Oscillator), the VCF (Voltage-controlled filter), and other voltage controlled components very rapidly, which is nearly impossible to do manually by a performer.
		It could also be used during a live performance to control lighting by using pre-programmed, timed pulses, and pre-programmed timed voltage levels.
	en.wikipedia.org /wiki/Roland_MC-8_Microcomposer (152 words)

	Guest - alcides lanza
		Filter Bank [FB]: octave filters, six of them on a panel, designated as A, B, C, etc. These filters could be used in series or in parallel.
		Voltage Controlled Filter [VCF]: built in 1957 [an improved version was produced in 1962] had a HI-Pass, LO-Pass filter, controllable by voltage.
		In essence, it was a polyphonic analogue synthesizer, utilizing voltage controllable sources and procedures, and operated by a keyboard with touch-sensitive keys.
	www.music.mcgill.ca /musictech/nime/alcides.html (534 words)

	[No title]
		Regarding to the functions, controls and in/outputs the module is identical to the 24dB low pass filter A-122 that is built around a CEM chip.
		Touching the sensor with a finger generates a control voltage CV1 that is proportional to the position of the finger.
		CV1 is controlled by the corresponding potentiometer (i.e.
	www.doepfer.de /presse/NAMM_Frankfurt_2003_e.txt (1193 words)

	Mutator Front Panel Controls
		The front panel controls for the Mutator are identical for both channels, with the exception of switch 11 which is detailed below.
		Even after the control input signal has died away up to 5 seconds of fade-out may be added by this control.
		Determines the amount of filter frequency sweep (up or down) being sent to the voltage controlled filter from the envelope follower.
	ourworld.compuserve.com /homepages/boomerang/mutatorf.htm (547 words)

	Operational Transconductance Amplifiers (OTA) for Synthesis of Voltage-Controlled Active-Filter Tuned Oscillators
		The voltage control made possible by th e use of the OTA enables the designer to synthesize oscillators with adjustable frequencies of oscillation.
		The advantages of the active-filter tuned oscillator are the independent control of frequency and amplitude, the control of the distortion in the output sinusoid, and the fact that any bandpass filter circuit with a positive gai n can be used.
		The use of the OTA as a replacement for the conventional op-amp in the bandpass filter portion of the circuit enhances these advantages by providing the circuit with independent voltage control of the frequency and the selectivity of the fi lter.
	et.nmsu.edu /~etti/fall98/electronics/grise/griseota.html (1988 words)

	og3 - Filter Bank
		The filter channels are voltage controlled state variable types with independently adjustable fc and Q. In addition, a common control voltage is sent to each filter.
		OTA U3:A forms the basis for voltage controlled Q. Boost/Cut functionality is achieved by summing a non-inverted or inverted signal into the Master Mixer circuitry.
		Commnon control voltage summer that sums frequency control voltage to be sent to all channels.
	home.comcast.net /~sbernardi/elec/og2/og3_filterbank.html (530 words)

	A-101-1 Vactrol Filter
		Both the A-101-1 Vactrol Multitype filter and the A-106 MS20 filter have their origins in the standard non-inverting amplifier low pass filter design (so-called VCVS low pass, VCVS = voltage controlled voltage source) shown on the left.
		The Q control potentiometer is replaced by a second current source that allows voltage controlled resonance.
		Even the filters of the MS20 are modifications of the basic circuit shown at the beginning.
	www.doepfer.de /a1011_tec.htm (782 words)

	Voltage controlled filter concept........
		I was wondering if anyone can direct a source of learning about voltage controlled filters?
		I understand that op amp filters ultilize capacitors and resistors to create phase shift between current and voltage of different frequency to generate the filter output response, however I havent been able to find books about using voltage to change the filter cut off frequency.
		range the Switch Capacitor is another way to have voltage controlled filters.
	www.edaboard.com /ftopic97266.html (100 words)

	Subtractive Synthesis- Basics, Waveforms, Filters, Envelopes, Modulation, Other Features - Yala Abdullah
		An Amplifier is used to control the loudness of the sound over a period of time so as to emulate a natural instrument.
		This is controlled by a parameter labled as "Cut-Off Frequency" (or "Cut-Off" or "Frequency").
		In Low-Pass Filters, the gradual rate of filtration (beyond the Cut-Off) is usually available as 4-pole or 2-pole filters (which are 24dB/octave and 12dB/octave respectively).
	groovit.disjunkt.com /analog/subs/2ansynth.htm (4463 words)

	Prophet 5
		The filter modifies the voice timbre under control of its four-stage envelope generator.
		Following each filter, a VCA (voltage controlled amplifier), also controlled by a four-stage envelope generator, shapes the voice amplitude.
		The filter and amplifier envelope generators are based on the CEM 3310.
	users.adelphia.net /~cygnusx_1/prophet5.html (737 words)

	OBERHEIM 2, 4, 6, 8 VOICE SYNTH ARCHIVE PAGE AUDIO PLAGROUND SYNTH MUSEUM
		All the essential circuitry necessary for a complete synthesizer voice is included: two voltage controlled oscillators (VCO's), a voltage controlled filter (VCF), two envelope generators, a low frequency oscillator (LFO) and a voltage controlled amplifier (VCA).
		Upon detection of a note depression, control signals are directed to an Expander Module as determined by the keyboard logic and the settings of the keyboard switches.
		That is to say, it is not enough to have four oscillators only to produce four part polyphony, but rather four complete voltage controlled synthesizer systems are needed, each one including not only oscillators, but also a filter, two envelope generators and a voltage controlled amplifier.
	www.keyboardmuseum.org /ar/o/ober/v.html (1911 words)

	Sub-Oscillator / Voltage controlled filter (Site not responding. Last check: 2007-10-08)
		The VCF is used to alter tone colors by cutting or boosting harmonics in the signals sent from the VCO.
		If the control is slowly lowered, it will begin to shave off the upper harmonics of the sound passing through the VCF.
		The effect will become stronger, the higher the control is raised.With the control at a high position, moving the CUTOFF FREQ slider will produce sounds peculiar to the synthesizer.
	www.yourvoice.se /sh09/subosc.html (434 words)

	[No title]
		This is an auto filter or auto wah, and it consists of two blocks, an envelope detector and a controlled filter hooked together in one circuit.
		By separating the two into an envelope detector module and a voltage controlled filter, we can do different things with both modules, as well as ganging them together in FXBus to be a Dr. Q.
		Converts the filter control voltage to a current for changing the collector resistance of Q1 Isolates the DC power to U1 from electrical trash that might be on the V1 power bus, and limits the current available to U1 under fault conditions
	www.geofex.com /Article_Folders/FXbus/fxbmod06.htm (1125 words)

	AMP, Alternate Music Press, The Multimedia Journal of New Music (Site not responding. Last check: 2007-10-08)
		By the summer of 1964, these were the components that we had assembled, the voltage controlled oscillators, the voltage controlled amplifiers, and the keyboard controller.
		The voltage controlled filter allowed the tone color changes in the sound to be affected rapidly, and analog synthesizers are distinguished more for their control filter capabilities than any other single function.
		It gives an immediacy, a physical ability to manipulate actual controls and connections who's effect a musician can easily hear, rather than a musician having to conceptualize it ahead of time by determining what sound he or she is going after in a digital instrument.
	www.alternatemusicpress.com /features/moog.html (2719 words)

	Articles - Phase-locked loop (Site not responding. Last check: 2007-10-08)
		A phase-locked loop operates in similar fashion, automatically raising or lowering the frequency of a controlled oscillator until it is matched to the reference frequency.
		Bang-bang control systems are simple, but are associated with significant minimum peak-to-peak jitter, because once in lock the phase offset hunts between the two extrema values of the dead band.
		From a control theory perspective, the PLL is a special case of the Kalman filter.
	www.sinoz.com /articles/Phase_locked_loop (2519 words)

	PAiA: SynthDrum Circuit
		Like most drum tone oscillators, the circuit is a very high Q resonant filter that is only slightly overdamped and on the verge of oscillating.
		As the CV-in voltage increases, the exponentially increasing current flow through these diodes causes their effective impedance to decrease, which raises the frequency of the twin-T network.
		The voltage on C4 is the Control Voltage, which decays over time as it discharges through R3.
	www.paia.com /syndrum.htm (637 words)

	Subtractive Synthesis- Basics, Waveforms, Filters, Envelopes, Modulation, Other Features - Yala Abdullah
		The Filter section of a synthesizer may be labled as VCF (Voltage Controlled Filter) or DCF (Digitally Controlled Filter).
		AMPLIFIER ENVELOPE - The amplifier section on a synthesizer may be labled as VCA (Voltage Controlled Amplifier) or DCA (Digitally Controlled Amplifier).
		To "modulate" is to exert control or affect or influence or shape.
	www.geocities.com /SunsetStrip/Underground/2288/t2ansynt.htm (4599 words)

	ipedia.com: Wah-wah Article (Site not responding. Last check: 2007-10-08)
		The electronic version, which sweeps the peak response of a filter up and down in frequency to create the sound, was first heard in 1945 on a pedal steel guitar created by Leo Fender and in the early 60s on Vox amplifiers (under the name wah-wah) and Thomas electronic organs (as the Crybaby).
		The variation in the peak response frequency of the filter resembles the change in formant frequency in the human vocal tract when saying the word "wah", making the wah-wah pedal a crude form of speech synthesizer.
		In electronic music, wah-wah effects are easy to produce by applying a modulation envelope to the voltage-controlled filter in an analog synthesizer.
	www.ipedia.com /wah_wah.html (536 words)

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