CEM3340/AS3340 - POT question

[fredrik]

Simplest sync is 1 nF capacitors between input and the corresponding pin:

AS3340 VCO /w hard/soft sync, FM modulation

The AS3340 example circuit uses a higher pulse out pulldown, and the onboard zener is a bit different so you can use a slightly lower Vee series resistor, but it works just fine with the CEM3340 values. The sync inputs expect brief spikes, and the example schematics just use 1 nF capacitors on the way in, to turn pulses into spikes: [image] EDIT: The 1222 performance VCO follows the example schematics, and routes the sync input via a 1 nF capacitor (C4). EDIT: I just noticed that the CEM334…

To add an octave selector, you need a precise voltage source (e.g. an LM4040 via a trimmer), then a precise voltage divider (e.g. rotary switch with precision or hand-matched resistors), then you inject the voltage by via a 100k resistor to pin 15, in the same way as the ones marked (A) on the picture here (CV in and tuning):

Oscillation problem on my VCO

So that looks like Sam’s simple layout with a few minor tweaks. I’ve marked the cv source voltages below. Measure them either at the resistors (A) or near the wires (B) relative to 0V (eg the rail marked below): [image]

(the 3340 will sum up all voltages, and generate a frequency corresponding to the total voltage).