Audio controlling circuits ( 32 ) :

• A Better Volume Control - how to create a log pot that is better than the "real" thing   
• Audio level control with resistive optocouplers - Controlling the level of an audio signal by means of an applied voltage or current has always been somewhat problematical but often desirable. . This application note deals with voltage or current controlled attenuators using optocouplers, primarily in relatively static situations.   
• Audio switching applications for resistive optocouplers - Electronically switching audio signals can be a more complex matter than it might first appear. Not only are there the obvious problems of interfacing between your control logic which is running off a 5V supply and something that is probably controlling a larger voltage swing, but there are the various imperfections of the switch element to consider, which can degrade your precious audio signal.   
• CMOS IC makes low-cost digital potentiometer   
• Constant Power "PAN" Control Circuit for Microphone for Microphone Audio Mixing
• Construction of a diy motorized volume control - Construction of a motorized potentiometer using a stepper motor for remote controlling/positioning of a standard audio preamplifier volume potentiometer (or whatever).   
• Convert voltage to potentiometer-wiper setting - This circuit converts an analog input voltage, VIN, to a proportional wiper setting of a DPP (digitally programmable potentiometer). The potentiometer's wiper setting, which varies from position 0 through 31, corresponds to the input voltage, which varies from 0 to 1V dc. Thedigital potentiometer used is CAT5114, a 32-tap potentiometer with an increment/decrement interface.   
• Digitally control gain over a �40-dB range - digitally control an amplifier's gain over a �40-dB range gain resolution of 1.25 dB   
• Digital stereo potentiometer - in pdf format, text in Finnish   
• Digital Volume Control - based on DS1669 Digital Pot IC   
• Elektroninrn potentiometri - electronic potentiometer for audio, text in Finnish   
• Fixed Attenuators - Fixed attenuators can be designed to have either equal or unequal impedances and to provide any amount of attenuation (theoretically) equal to or greater than the configuration's minimum attenuation - depending on the ratio of Z1/Z2. Attenuators with equal terminations have a minimum attenuation of 0 dB. Unequal terminations place a lower limit on the attenuation.   
• Gain Control - Applications as disparate as test equipment, audio, medical imaging, and cellular base-station radios need to manage signal amplitudes in the analog domain. This article tells about those applications.   
• Inexpensive relays form digital potentiometer - build a digitally controllable isolated potentiometer which can tolerate voltages up to 60V dc   
• Improve FET-based gain control - One problem with standard FET gain-control circuits is increased noise when you use the FET as a part of a resistive attenuator in series with an op amp. When you substitute the FET for the gain-setting resistor in a noninverting op-amp circuit, distortion limits the circuit configuration to applications in which the input voltage is less than a few hundred millivolts.   
• Linear potentiometer implements logarithmic gain control - trimmer potentiometers are ubiquitous components and are available in a variety of packages, resolutions, and temperature stabilities but none of these potentiometers implements anything but the usual linear function of resistance vs shaft position as useful in many audio applications   
• Nine Ways to Adjust Signal Level - This article describes few different ways to adjust audio signal level.   
• Op amp linearizes attenuator control response - Professional-audio equipment commonly uses Analog Devices' (www.analog.com) high-performance, quad-voltage-controlled SSM2164 attenuator. The control response is -30 dB/V, with 0V producing unity gain. Attenuation increases as the applied control voltage increases in the positive direction. This circuit extends the range of applications for this versatile chip by providing a simple means of linearizing the control response. The result is an amplifier with gain directly proportional to the control voltage.
• Op amp linearizes response of FET VCA - FETs find common use in VCAs (voltage-controlled amplifiers) and attenuators, in which the FET serves as a variable resistance. A control voltage applied to the gate sets the channel resistance and overall circuit gain. You frequently need to select individual FETs because of wide spreads in FET characteristics. This circuit uses a master-slave servo technique with a matched-FET pair to implement voltage-controlled variable gain. In this circuit the gain increases linearly from -55 to 0 dB as control voltage varies from 0 to 5V.    Rate this link
• Printer port activates CMOS switches - This cost-effective design provides control for CMOS switches without the need for an external power supply   
• Programmable-gain amplifier is low-cost - Numerous programmable-gain amplifiers are available, but a simple solution provides the option of using 256 gain steps with an 8-bit DAC and higher steps with higher bit DACs.   
• Single stage gives logarithmic gain steps - by placing a variable component in the positive feedback loop of an op amp, you can vary the gain of the stage logarithmically with respect to a linear resistance or conductance   
• Single switch controls digital potentiometer - The control of electronic potentiometers in most today's applications comes from controller-generated signals. However, a significant number of applications exist that require adjustments using manual, front-panel controls. This circuit uses one IC, one switch, and 10 discrete components. It implements the interface of a single DPDT, momentary-contact rocker switch to a DPP (digitally programmable potentiometer) that has a three-wire increment/decrement interface.   
• Single switch controls digital potentiometer   
• Tack a log taper onto a digital potentiometer - idea to convert linear digital potentiometer to a logarithmic digital potentiometer   
• Technical Secrets of the Crossfader - A crossfader is designed to predictably control the outputs of two separate mixer channels based on the relative position of the fader's knob between its endpoints. It's a simple sounding task but there are many different ways the job can be done, electrically and mechanically. This document describes some of the most commonly used ones. Most crossfader circuits are implemented in one of two basic schemes.   
• Variable-gain stage uses voltage-output DAC   
• VISW 8 x 4 Stereo audio/video router   
• Voice-Over Circuit - swiches automatically from sound source to microphone when enough sound comes in from microphone   
• Voltage controlled amplifier - three different circuits   
• Voltage Controlled Audio Panner - variable gain amplifier circuit   
• MOSFETs reduce crosstalk effects on analog switches - Some cost-effective analog multiplexer/demultiplexer ICs, such as the CD4053 and CD4066, find frequent use as signal distributors. These digitally controlled analog switches have low on-resistance. However, with all channels in the same package, crosstalk can be annoying and unavoidable. The circuit presented in this article provides a cost-effective and viable method of solving this problem.   

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