[sdiy] Four pole highpass with OTAs, based on Polyfusion (student project demo)

[Aaron Lanterman]

Last one for tonight, in two parts:

http://www.youtube.com/watch?v=d9tphjlyp2U

http://www.youtube.com/watch?v=CCUyOX3QuNs

This one was a lot of fun; at the end we're using two LFOs, running at different rates, one controlling the resonance and the other the cutoff. At the end, we start controlling them with audio VCOs. :)

Speaking of which... David originally had J201s for his JFET buffers after each OTA, and had all sorts of problems with DC offsets at the output of his buffers. As a lark, I gave him some MPF102s and had him try those instead, and the DC offset problems went away. Any idea what was going on there?

I know how to recognize a few simple transistor circuits, but I am not zen in their ways. I'm really a DSP guy, who somehow wound up teaching an entirely analog circuits based class...

- Aaron