Here is the pitch 2 voltage converter for my Shakuhachi 2 Synth project. It is based on an article in Electronotes EN#84 p5-p9 from Robert Iodice. It consist of some control logic and a 12bit DA converter. I have found a fault in the control logic and simplified the DA converter. The original only had a V/Hz output, so I added a V/Oct output.

Pitch 2 voltage converter: schematic

The circuitry takes a pulsetrain and converts it to a voltage according to the frequency of the pulsetrain.

Pitch 2 voltage converter: timing diagram

A clock of about 320kHz is used to drive a 12bit binary counter. The outputs of which are fed through latches and then to a 12-bit DA converter. The voltage is then converted to V/Oct characteristic with a anti-log generator. The additional circuitry is to control the timing sequence, gating the clock signal and generating a flag signal. The flag is generated when the outputs of the counter all reach a high level. This condition is reached when the input is removed or the input frequency drops below the systems lower frequency limit.

The circuit has the advantage of sampling very quickly (only two pulses required) and holding indefinitely.

Pitch 2 voltage converter: stuffed PCB

Pitch 2 voltage converter: Front

Pitch 2 voltage converter: Back