This is the exact same circuit as the CA3046 VCA
but uses a CA3086 transistor array. Because the transistors in
the CA3086 aren't matched as good, the offset trimmer had to be
increased to 10k.
The results show that there is no performance difference between the CA3046 and CA3086 as long as you trim the DC offset. Without trimming, the CA3086 has a lot higher offset error, which result in control voltage bleedthrough.
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||83 dBr A|
|0 V CV, no signal||107 dBr A|
|0 V CV, 1kHz 10 V p-p in||88 dBr A|
|0 V CV, 2 kHz 10 V p-pin||80 dBr A|
|0 V CV, 10 kHz 10 V p-pin||64 dBr A|
|Headroom (over 10V p-p)||5 dB|
|CV bleedthrough||with careful trimming||5 mV|
The CA3086 is fully usable, but if you can get the CA3046, it the better part.
Low CV bleedthrough
Fairly low distortion over a wide range of signal levels
Fairly high signal bleedthrough