Schematics / Nicolas Super Simple V Per Hz VCO
Nicolas' Super simple V/Hz VCO modified by Phobos ,from this topic : http://electro-music.com/forum/post-363816.html I had build Nicolas' Super simple V/Hz VCO succesfully before and since it's a pretty simple circuit (for a VCO) I decided to use it for this synth aswell. The first change I made was to get the amplitude up to +/-5Vpp I tried a couple of things and I think the 4 diodes are actually a leftover from those experiments. But the easiest thing to do was just to add an extra output amp. The highest frequency is allready limited by the circuit itself so with the resistor values I choose it doesn't matter if the CV get's above +5V, the frequency just doesn't get higher. On the low end however the thing starts acting a bit weird and then stops, so; zenerdiode limiter to the rescue. As you can see this time I used the variable zener diode circuit I found which makes it much easier to set the correct limit. and then there is the resistor capacitor network on the input. Allthough my LFO's didn't seem to have any spikes according to my scope (I added some caps to surpress those), the squarewaves did seem to cause some peaks on the output of the VCO. so I experimented a bit which some different cap/resistor placements untill they were gone. the frequency range might seem a bit limited but remember it was originally designed for a dronebox. I also designed a sinewaveshaper with some diodes and a vactrol VCA but didn't have enough panel space. So it will probably end up in a seperate case.