555 VCO PCB/Panel

Fonitronik's Eurorack design of the Thomas Henry 555 VCO.

This is a PCB/Panel set in the Eurorack format.

Availability: In stock




From Thomas Henry, announcing the original design of the 555 VCO:


Hi all, 

As alluded to previously, I have four projects that have been sitting around way too long and have been panting to get out the door for the past couple of years. 

So, here's the first: a VCO using easy to find parts. If I may be so immodest, this is my best design to date. The waveforms look great and if you check the measurements, below, you'll see it's the most accurate I've ever come up with. If I were younger and had more energy, I'd turn this into an article and make some moolah from it. Unfortunately, my strength for such endeavors is ebbing, so instead I'll post it here for you to play with. All I ask is that you respect the rights and don't republish the design or rip it off for any commercial purposes. I'm not opposed to someone doing a PCB for noncommercial uses, but please secure permission from me first. 

Okay, without that out of the way, here's the dope. My favorite VCO of all times is the CEM3340, and I've always wanted to approximate it somehow. After nearly thirty years, I finally have a design which comes the closest. The accuracy on my breadboard was very good. 

There are ramp, triangle, pulse and sine outputs, all of which are decent looking. The sync is a real treat and basically comes along for free. And, of course, there are the usual VCO features such as coarse and fine tuning, exponential and linear FM, etc. If you're looking for cleverness, then be sure to check out how I did the sync, the ramp, and buffered the sine to keep the chip count down. 

Specs & Downloads

Specs & Downloads

manufacturer Fonitronik
HP 16
Depth No
+12V 26mA
-12V 24mA
+5V No
Additional Resources Build Guide


Customer Reviews (1)

Great bang for your buck VCO!Review by isohedra
i really love this vco.
the build isn't too bad, maybe approaching intermediate skill level.
well laid out pcb, but you need to reference the muffwiggler thread.
several resistors need to be changed or were labeled incorrectly in the original build guide.
(it's only like 3 resistors, not a big deal)

killer sync sound, and good points of calibration.
if you've never calibrated a module it helps to have some kind of oscilloscope.
not absolutely required however.
more important if you want accurate octave steps and precise wave shapes on your
sine / ramp.

make sure to reference the muffwiggler build thread before building!
(you can also get build help / troubleshooting there) (Posted on 8/13/2016)

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