CA3080 VCA 2

This is the same circuit as the CA3080 VCA 1, except for the output stage. The chip is also driven a little harder. The load resistor is connected in the feedback loop of an operational amplifier. Here a 15 year old RCA chip is used. The performance of this circuit is slightly better than the CA3080 VCA 1. This probably has more to do with the increased Iabc than with the different output configuration. This circuit actually isn't much noisier than the SSM2024, but the signal bleedthrough is around 10 dB higher.

Noise & signal attenuation

Red = signal bleedthtrough at 0V CV. Blue = 10V CV, no signal. Green = 0V CV, no signal.

Distortion (THD+N) vs. input level

Frequency response

Test results

Dynamic range 10 V CV, no signal  81 dBr A
  0 V CV, no signal 110 dBr A
  0 V CV, 1kHz 10 V p-p in 85 dBr A
  0 V CV, 2 kHz 10 V p-pin  77 dBr A
  0 V CV, 10 kHz 10 V p-pin  67 dBr A
  Headroom (over 10V p-p)  5 dB
CV bleedthrough with careful trimming 2 mV



This was expected to be a poor performer but turned out to be quite respectable. It is a little noisier but the difference is surprisingly small. This circuit seems to be less noisy than the other CA3080-based ones.


Very low CV bleedthrough

High signal bleedthrough at higher frequencies