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Questions tagged [voltage-controlled-amplifier]

For questions about voltage controlled amplifiers (VCAs).

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Voltage Controlled Amplifier using Oscillator

I have found an example of a voltage Controlled amplifier using a square wave control on this page I'm trying to modify it using my own control signal, a triangle wave from Low frequency oscillator. ...
miguelfuzz's user avatar
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1 answer
46 views

Scale and offset voltage range from DAC to VCA

Still tinkering with my VCA based effect mixer. I control multiple DACs (MCP4922) which send control voltages to the VCAs (AS2164). Until now I've just fed the DACs a reference voltage of 3.3V to ...
Jesper Kragh's user avatar
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2 answers
105 views

Why are MOSFETs called voltage controlled devices even though we have to push in charge/current to charge the input capacitances?

I was wondering why MOSFETs are called voltage controlled devices when the input capacitances of the MOSFET (Cgd and Cgs) need to be charged in order to turn ON. Wouldn't that mean that they are ...
Sudhanva Gokhale's user avatar
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1 answer
63 views

Calculation of unity level (0dB) after gained VCA

Basically I'm controlling a VCA (AS2164) with my Arduino through a 10 bit DAC. All is working well. The VCA output is then gained x 3.3 though an op amp, which in my calculator gives a 10dB boost. The ...
Jesper Kragh's user avatar
2 votes
2 answers
157 views

Splitting an audio signal. Different paths give different output, but shouldn't. I may not understand impedance

I have this simple audio circuit. Guitar goes in. I buffer the signal. I split the signal into two. One goes directly out (OUT A), and one goes into a voltage controlled amplifier and out to another ...
Jesper Kragh's user avatar
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0 answers
69 views

Fine-Tuning a Circuit After changing VCA (SSM2641 to SSI2164)

A friend's accident led to a fried SSM2641 VCA in an Eurorack audio module. Determined to give it a new lease on life, I'm diving in, though VCAs are not my forte. After searching for hours, it seems ...
flower.fish's user avatar
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1 answer
68 views

LTspice simulation with diode in op-amp feedback does not match reality. why?

I want to change the curve characteristics of a vca-input signal (DC). So I simulated a circuit that I found on the internet (which is part of a commercial device so I suppose it should work): The ...
linsensuppe0815's user avatar
0 votes
2 answers
94 views

Voltage-controlled amplifier output offset

I'm testing a voltage controlled amplifier circuit in a simulator. The circuit is powered by a single 9V supply, so a "virtual ground" equal to 1/2 VCC is used. I have a question about the ...
Alex_G's user avatar
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1 vote
1 answer
214 views

LM13700 does not completely reduce the sound

I have a problem with LM13700 - it does not completely reduce the sound when the control current is zero. For testing, I put together the most basic circuit, where the control pin is connected to the ...
Alex_G's user avatar
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0 answers
248 views

Voltage controlled amplifier with single supply

I'm trying to make a voltage controlled amplifier circuit to control the feedback level of a delay effect. My big problem is that the circuit must be powered by a single power supply. I seem to have ...
Alex_G's user avatar
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-1 votes
1 answer
148 views

How does the attack / release element of this audio compressor function?

This is an audio compressor circuit based on (and designed by the makers of) the THAT 4301. U2B converts the AC input to RMS, which is then inverted by U2D. When there is no signal input to the ...
Josh Taylor's user avatar
1 vote
1 answer
376 views

Single transistor VCA for gate type CV signals

I am in the process of designing a sort of mini synth / noise machine and I'm struggling with the output stage. I only want sound to come out when I press the button, so based on some designs I have ...
Javier Soto's user avatar
0 votes
1 answer
160 views

Trouble with VCA as signal amplitude control

I designed (and tested) the classic analog multiplier composed with operational amplifiers. However, the voltage resulting from the operation did not correspond to the product of the input voltages. ...
Borg Drone's user avatar
2 votes
0 answers
191 views

Long tail amplifier using current mirrors

I have built this in the Multisim simulator and it works there as desired. Now I have built it on a "lame" breadboard. Is the upper PNP current mirror correct? Since the "left" ...
NaturalDemon's user avatar
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0 answers
298 views

How to amplify a signal from a function generator from 5V to 35V?

I have a function generator that has an output voltage of 10Vpp. I need to use it to drive a voice-coil-actuator (VCA) that operates on 35V and 11.7A. I was searching for a solution to amplify the ...
Power's user avatar
  • 31
0 votes
2 answers
1k views

XLR phantom power microphone mute, redux

Wall of text? Feel free to jump to the four related questions towards the bottom! I had a previous post discussing how to build a pop-free, electronically controlled mute circuit that goes inline in a ...
Jon Watte's user avatar
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1 vote
3 answers
437 views

Drive a VU meter negative from "0dB" to show compression with VCA compressor

I have a simple VCA compressor based around the THAT 2180 VCA. http://www.thatcorp.com/datashts/dn115.pdf I would like to use a standard "VU meter" to indicate compression, but work in "...
jackwarner's user avatar
1 vote
2 answers
328 views

LM13700 control current appearing as voltage at output?

I've got an LM13700 in this VCA configuration, and for whatever reason the gain control input (I'm applying a triangle LFO, ranging from 2-7v) is appearing as a voltage at the output. Does anybody ...
Jonathan Donald's user avatar
3 votes
1 answer
360 views

Digitally-Controlled Analog Processing for VGA Video Signal?

A few months ago, I replaced the dead fluorescent backlight of an LCD computer monitor with an 8-bit-per-channel RGB LED strip, and built a controller for it from an AVR microcontroller that talks to ...
AaronD's user avatar
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0 votes
1 answer
298 views

OTA ca3080 troubles

I having a hard time getting this OTA ca3080 circuit working as expected. It's configured as VCA (or a amplitude modulator. I got the circuit from here: http://www.idea2ic.com/LM13600/UsingOTAs2.pdf I ...
user3810130's user avatar
1 vote
1 answer
774 views

Having trouble with OTA CA3080 making a VCA

I'm having trouble getting this CA3080 OTA to work properly. :-( I watched this video ( https://www.youtube.com/watch?v=BbaJ6TOmyVo ) which is quite helpful, but I'm missing a few cues here... In ...
user3810130's user avatar
0 votes
0 answers
705 views

VCA on 5 V power supply

I've made a VCO and ADSR-generator with two Arduinos. The VCO uses a DAC made with a resistor ladder, the ADSR-gen uses a 12-bit DAC. Everything is 5 V powered (USB charger of 1 A). In my search for a ...
user3810130's user avatar
1 vote
1 answer
1k views

Trying to make fuzz factory with CV inputs

I'm trying to construct some kind of fuzz factory modular from regular fuzz factory pedal. Circuit of the original pedal is pretty easy, but I've tried to add some VCAs based on LM13700. Honestly, I'...
drdrvv's user avatar
  • 11
3 votes
3 answers
3k views

Design of an Automatic Gain Control Using a JFET

simulate this circuit – Schematic created using CircuitLab I have implemented the above circuit which is supposed to amplify a negative 200kHz sinusoid to constant amplitude even if the ...
Simon Sultana's user avatar
2 votes
1 answer
253 views

What's the purpose of this circuit section?

I'm experimenting on VCA circuits and found the same (or similar) pattern in many linear VCA projects found in internet using LM13700 OTA. The specific section I'm curious is made by an Op-amp, a ...
Adam Calvet Bohl's user avatar
2 votes
2 answers
914 views

Why does this JFET attenuator distort the signal this way?

I have been trying to build a simple VGA using an op-amp and JFET for gain control. I get good results over a small range of voltages (like factor of 10) but as soon as I try to improve this, the ...
Felix S's user avatar
  • 798
1 vote
1 answer
863 views

How to understand V2164 VCA control voltage per dB?

I'm designing an audio circuit which includes the V2164 VCA IC. This chip is a clone of SSM2164. I take a "Basic VCA Configuration" circuit which is supposed to give a unity gain with 0V control ...
Volodymyr Smotesko's user avatar