Voltage Controlled Amplifier – VCA
This is a Voltage Controlled Amplifier (VCA). A VCA board helps users control the Audio Level from a remote potentiometer. It requires a single-ended audio signal in the input. Gain control voltage can be adjusted through an on-board potentiometer or use an external potentiometer connected to CN4. The project works with a dual ±15V power supply. Screw terminal connectors are provided for signal input and signal output. The project is built using THAT2181LA chip, a VCA that is designed for high-performance audio-frequency applications requiring exponential gain control, low distortion, wide dynamic range, and low control-voltage feedthrough. These parts control gain by converting an input current signal to a bipolar logged voltage, adding a DC control voltage, and re-converting the summed voltage back to a current through a bipolar antilog circuit. Stereo control of VCA with a single potentiometer is possible.
THAT 2181-series trimmable Blackmer voltage-controlled amplifier (VCAs) ICs are very high-performance current-in/current-out devices with two opposing-polarity, voltage-sensitive control ports. They offer wide-range exponential control of gain and attenuation with low signal distortion.
Trimming
The trim should be adjusted for minimum harmonic distortion using PR1. This is usually done by applying a middle-level, middle-frequency signal (e.g. 1 kHz at 1 V) to the audio input, setting the VCA to 0 dB gain, and adjusting the SYM trim while observing THD at the output. In THAT2181LA, this adjustment coincides closely with the setting which produces minimum control-voltage feedthrough, though the two settings are not always identical.
Features
- Power Supply +/-15V DC @ 40mA
- Gain Range -100dB Min-+20dB Maximum
- Total Harmonic Distortion 1V 0dB Gain 0.0025%
- Screw Terminal for Single-Ended Audio Input
- Input Impedance, Audio 20K Ohms
- Screw Terminal for Audio Output
- On Board Power LED
- 5mm Mounting Holes
- PCB Dimensions 60.96 x 23.50 mm
Connection
- CN1: Pin 1 = Audio Signal Input, Pin 2 = GND
- CN2: Pin 1 = Audio Output, Pin 2 = GND
- CN1: Pin 1 = +15V DC, Pin 2 = GND, Pin 3 = -15V DC
- R9: Gain Adjust Potentiometer
- CN4: Optional External Gain Adjust Potentiometer
- D1: Power LED
Share
This is a Voltage Controlled Amplifier (VCA). A VCA board helps users control the Audio Level from a remote potentiometer. It requires a single-ended audio signal in the input. Gain control voltage can be adjusted through an on-board potentiometer or use an external potentiometer connected to CN4. The project works with a dual ±15V power supply. Screw terminal connectors are provided for signal input and signal output. The project is built using THAT2181LA chip, a VCA that is designed for high-performance audio-frequency applications requiring exponential gain control, low distortion, wide dynamic range, and low control-voltage feedthrough. These parts control gain by converting an input current signal to a bipolar logged voltage, adding a DC control voltage, and re-converting the summed voltage back to a current through a bipolar antilog circuit. Stereo control of VCA with a single potentiometer is possible.
THAT 2181-series trimmable Blackmer voltage-controlled amplifier (VCAs) ICs are very high-performance current-in/current-out devices with two opposing-polarity, voltage-sensitive control ports. They offer wide-range exponential control of gain and attenuation with low signal distortion.
Trimming
The trim should be adjusted for minimum harmonic distortion using PR1. This is usually done by applying a middle-level, middle-frequency signal (e.g. 1 kHz at 1 V) to the audio input, setting the VCA to 0 dB gain, and adjusting the SYM trim while observing THD at the output. In THAT2181LA, this adjustment coincides closely with the setting which produces minimum control-voltage feedthrough, though the two settings are not always identical.
Features
- Power Supply +/-15V DC @ 40mA
- Gain Range -100dB Min-+20dB Maximum
- Total Harmonic Distortion 1V 0dB Gain 0.0025%
- Screw Terminal for Single-Ended Audio Input
- Input Impedance, Audio 20K Ohms
- Screw Terminal for Audio Output
- On Board Power LED
- 5mm Mounting Holes
- PCB Dimensions 60.96 x 23.50 mm
Connection
- CN1: Pin 1 = Audio Signal Input, Pin 2 = GND
- CN2: Pin 1 = Audio Output, Pin 2 = GND
- CN1: Pin 1 = +15V DC, Pin 2 = GND, Pin 3 = -15V DC
- R9: Gain Adjust Potentiometer
- CN4: Optional External Gain Adjust Potentiometer
- D1: Power LED
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