[sdiy] JH's discrete 2040 clone

[JH.]

> Does anyone know how closely related the MOTM-440/JH clone is to the
> original circuit inside the SSM 2040? My impression was that the circuit
> topology was based on deduction and analysis, but did anyone ever track
down
> a schematic? Or were they all destroyed by PMI?

The 2040 was designed by Dave Rossum.
I asked him about the circuit, and he remembered it very well.

> Also, can anyone describe the nonlinear effects of the SSM 2040, as to how
> they differ from the Moog ladder?

You have the usual nonlinearities of any OTA- or ladder-based LP VCF, and
then
you have some very special transient behaviour which you normally find in
tube
amps when the the grid goes positive.
I think there's a lot of it in the AH archives.

> P.S. I work at Analog Devices (which acquired the SSM line), and have
asked
> around if we have the SSM 2040 schematics, with no results.

I've never seen 2040's from AD. I think PMI still carried them, but not AD.

JH.