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
|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