Specification
- Function
- Voltage Controlled Amplifier
- Width
- 4 HP
- In rack
- 1
- Built
- 2026
- Revision
- A
- Status
- Built
Voltage Controlled Amplifier · 4 HP
Voltage Controlled Amplifiers
After adding the slew limiter / envelope generator to my rack, I found that I was down a couple of voltage controlled amplifiers (VCAs), and I needed to add some VCAs if I truly wanted to use the new envelope generator. Simple fix, just build Moritz Klein's design for a dual VCA.
The voltage controlled amplifiers are two transistor-based VCAs which accept an input signal and control voltage for the level of attenuation applied and then output the attenuated signal to the output. Each VCA also has an offset knob if you manually want to attenuate the signal, and it is also helpful if using a low frequency oscillator. The VCAs aren’t geared for negative voltages, so setting the offset knob at the twelve o’clock position gives a full range of attenuation for a low frequency oscillators spanning -5 volts to +5 volts.
My only changes to Moritz Klein’s original design were shrinking the size from 6 HP down to 4 HP by using some surface mount components and a second PCB, and I omitted the interconnect which normalled the two VCAs together in the original design.
