Hi can you use a cheap pulse generator kit from aliexpress etc… as a voltage controlled oscillator…VCO? Greetings tygho
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Nope. You can’t trivially add voltage control to a non voltage controlled oscillator.
Also from here it appears the frequency is more or less fixed at ~1 kHz, the trimmer affects both the frequency and the amplitude, and the maximum amplitude is 0.5 V — way too small.
What’s your goal? To make a cheap VCO? Keep in mind the most expensive parts of a module usually are the pots and switches, which you’d have to add to this even if it were feasible. Other than those the onboard parts for a simple stripboard VCO would be pretty cheap, with a 3340 design the chip would be the most at around $7, everything else on the board would add up to maybe $5 or so more. That’s not 0.52 euros I admit, but it’s not much, it’d work, and again you’d have to add the more expensive pots and switches anyway.
Even for a non voltage controlled LFO it’d probably be easier to build one from scratch than to try to modify this for it.
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Thank you very much!!
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I’ve used a cheap function generator as an LFO. it works quite well and it allows me to control the voltage output as well as the frequency, plus it has plenty of waveforms to choose from and programmable sweeps.
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Thats realy cool!!! What generator do you use for that? And how did you connect it i will realy like it!! Thanks for your message! 
This is the one I got, it’s pretty generic, the brand is koolertron but there’s dozens of others just like it sold under different brands. I think this cost about $100. I just connect it using the bnc to alligator cables that it comes with, clamp the positive to the tip of a TRS cable and the negative to the sleeve and plug it in to the CV input on oscillator or other modules. The output voltage can be varied all the way up to 20V so I’d make sure to check the data sheets on whatever your connecting it to to make sure you don’t fry something. I plugged it into an Atari punk console and briefly cranked it all the way up to 20V without any issues but it sounded best between 4-8 volts. I think it would be a fun project to turn this into a Kosmo module, the pcb inside is only a tiny fraction of the enclosure that it’s in and could easily be removed and mounted on a panel.