PORTA-1A

Dual Portamento - scratch built

The design for this module came from Bluebear Enterprises. It's has exponential portamento with a rate control, a CV input and a CV output. It's simply a pot in series with the CV input with the wiper connected to a charging capacitor to ground. The resulting slewed wave is bufferred with an opamp.

I found that patching the portamento into a VCO changes the initial pitch about an interval (half step), and there is no facility for trimming this particular design. I'd really like to try a different circuit in the future; I'd probably choose a design with seperate up and down rates and a gate input for turning glide on and off.

---