Calibrating and tuning a VCO

Let’s look at how to set up a VCO to track at 1 volt per octave (1 V/oct). This will apply to many VCO designs but I’m thinking particularly of 3340 based designs such as the LMNC 1222 Performance Oscillator or my Hero and Sidekick VCOs. The idea is to get the pitch to change […]

This is the Hero VCO, my new voltage controlled oscillator. It started off as kind of a mashup of the Kassutronics VCO 3340 and the LMNC 1222 VCO. You can still find traces of both in the schematic, as well as bits of the Thomas Henry VCO Maximus, although little has evaded modification. Like those, […]

Video: March of the Modules of March

All in a week’s work

I built two modules this week: I haven’t installed these in the case yet, but when I do, that will be Kosmodrome Phase I complete. The envelope generator is a duplicate of the Kassutronics Precision ADSR I made previously. The VCO is a new design, part of a larger project which I’ll write up when […]

VCO chip tests, part 2

Recently I went back to looking at the AS3340A on a new breadboard setup, and at first I thought I’d have to eat many of my words on the subject: Well crap… the pulse width frequency shift is back, with -5 V regulator power. I don’t know why, I thought I’d pretty much ruled it […]

VCO chip tests

tl;dr: My tests with AS3340 chips appear to indicate: (1) Pulse width frequency shift is seen with both AS3340 and AS3340A chips; (2) Using a regulated -5V on pin 3 does a good job of suppressing the pulse width frequency shift; capacitor from pin 4 to ground does not work; large resistor between PW CV […]

VCO re^{n}dux

Having improved the LFO pulse width range yesterday, I went ahead and improved the VCO’s today. This time the fix was to increase the gain of the amplifier I’d added from 1.33 to 2.0. That involved changing out two resistors, but actually I decided it might be just as well to build a new amplifier. […]

VCO victory surrender

I checked and as expected, the MFOS VCO has the same problem as the LFO: with an attenuator on the PWM CV, changing the attenuator changes the pulse width even with no CV plugged in. I applied the same fix, replacing the 100k pots with 25k and the 10k mixing resistors with 200k. I found […]

Tag: vco