Prompted by a comment on my System 100 VCA stripboard post, for as much use as it is here’s a very quick comparison of the original System 100 VCA and a clone System 100M VCA, built on stripboard with a BA662 clone for the OTA.

No envelope tweaking, just a bit of VCF variation from CV2 on the MC-4, and then full-gas into whichever VCA.

Here’s the stripboard clone 100M VCA, behold:

This is the (non-clone) System 100-only demo:

And this is the System 100 played through the clone 100M VCA (set on linear response), using the System 100 envelope as a CV source.

The System 100 has a lower output envelope than the 100M, so the 100M VCA is super-quiet when triggered from the 100 when set to exponential response. Flipping the VCA to linear gives you a usable audio level to play with.

The VCOs in my 100M clone are a couple of Curetronic boards, both using a heated CA3046 in place of the ua726. I’m not convinced the scaling is totally right on either VCO, so try and ignore that. Here’s a quick test of the VCO waveforms played through the System 100 VCF and VCA. You’ll hear:

1. System 100 square, low VCF, mid res
2. 100M square, low VCF, mid res
3. System 100 sawtooth, low VCF, mid res
4. 100M sawtooth, low VCF, mid res
5. System 100 PWM’d square, open VCF
6. 100M square, open VCF
7. System 100 sawtooth, open VCF
8. 100M sawtooth, open VCF

and if you can take it, here are some sweeps, 100 then 100m, in the order

1. sawtooth
2. square
3. PWM square
4. triangle wave

That’s too much excitement for now, I’m going for a lie down.