redesigned the expo converter, again

The output current of the expo converter is now (100nA < Iabc < 2mA) which means a more logarithmic response of the VCF, more like the IR3109.

btw this is a one pole LP filter, not a two pole

VCF sound like this now:

Juno2poleFilter-v2 by sinneb

and here’s the real 2 pole LP filter:

Juno2poleFilter-v3-real2pole by sinneb