Super simple V/Hz VCO

[nicolas3141]

This VCO is not that great in terms of stable tracking, but it depends a lot on what your idea of "in tune" is and what range you are going to use it over. With the yamaha VCO giving your ears the central pitch it doesn't matter if the extra VCOs are a little bit off, especially if they are also being modulated by an envelope or LFO. I suspect that two octaves of "in tune" tracking might be difficult to achieve, but over one octave it might be okay. If you are building a CV interface between the two, you have the opportunity in that circuit to add tweaks to improve the linearity. That is how most VCOs do it - usually somewhere in the CV interface (ie the expo converter usually) there will be some trimmers to boost the high and low ends where a simple VCO tends to go flat.

I know of one person who has got these VCOs under midi control, but he is using a PC interface and software which has a tuning calibration function. So when in tuning mode it outputs various CVs, listens to what pitch they generate and then builds a custom function to derive the correct CV for each midi note.

But the great thing is these are so simple that you could just build one and try it out. If you don't like it as an audio VCO, you can always swap the timing cap for something bigger and use it as an LFO. You can never have too many LFOs

Cheers,
Nicolas

[anders79]

Thanks for the reply Nicolas!

Ok, it would be nice to have a little wider range than one octave of good tracking, but I give it a try. I am going to start another thread about my project with extra VCOs for the CSY-1. Also, I am definately going to try out your VCF! It looks so simple so maybe I would try two of them in series, with the resonance going back from the second filter to the first one. That is to make the filter sweep stronger and sharper, maybe it can sound more like minimoog-VCF in that way Have you tried that?

kind regards Anders

[darkomen]

Hi, I'm new to building synths and I was interested in building this VCO and I had some questions.
I see there is a switch on the CV in, which I am assuming it is the switched socket, but I'm wondering what its purpose is? And does anyone have an example of a switched socket maybe from mouser or the like, tried looking for it but not too sure if I was looking at the right thing? And more of a general question because I see this on a lot of other synth schematics, but what's the purpose of the 100k pot coming from the CV input?

Thanks!

[Ojd]

When nothing is connected to CV in it connects to steady pos voltage, thus making pot to control the pitch. Its basically initial tuning + (optional) modulation - these are the minimal controls of the vco.

[darkomen]

Thanks for the explanation.
And I built this over the weekend and tested it out, works really well!

[lintang]

hi nic..
i`m nubie...

i plain to build this VCO, i see the 6v input in the corner of the schematic.. and i read the explaination on this tread this voltage has function to keep the note/tune on C.

1. i breadboard last night i can use this voltage (6V) to manual pitch control using pot, but why on the bottom CCW pot got frozzen ? can i put some resistor to break the problem

2. i the schematic we see u use switch to on/off the 6V input, if i actived 6V voltage, can we used together with the CV...? Or i need some tread to get 2 function.


My goal i have 2 mod 1st CV input depth and 2nd tune/pitch control (can use manual or control by CV together)



thank`s


LINTANG

[mrand]

Regarding the tri core VCO Nicolas posted here:

"If you want to try this on +/-15V it might be okay, but you may need to put in an additional protection diode for the transistor."

What would this look like?

Returning to this handy circuit which was my first diy build a few years ago