Hi

>> http://www.doepfer.de/a170.htm
> Thanks Julian. Ahhh....so much more to buy.

The A170 is of course capable of doing a lot more than smoothing
squarewaves (Portamento, AR-Envelope, creating time dependend
differential values...). But if you just want to smooth the edges, and
you are able to solder, you might try to create a simple passive lowpass
adaptor cable. Requires a capacitor and a resistor.

Florian