CA3080 VCA 2

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 I_abc 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

Summary

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

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• High signal bleedthrough at higher frequencies