A Mess Of Wires Turned Into An Analog Synth

Over on YouTube, [GumpherDM3] built one of the greatest musical projects we’ve seen in a long time. It’s an analog synthesizer that is one of a kind. It’s going to stay one of a kind, too: no one would ever want to copy this mess of wires and perfboard that was successfully turned into a complete musical instrument.

The design of this synth is what you would expect from something that draws its inspiration from semimodular synths such as the Minimoog and Korg MS20. There are four VCOs on this synth, two audio and two used for the LFOs. A four-pole low pass filter, VCA, and two envelope generators round out the purely analog portion of the build. There’s an arpeggiator in there too, which makes for a really great demo video (below).

Inside, this is a true analog synth with the VCOs, filter, and VCA built around the LM13700 transconductance amplifier. The build log shows these chips spread out around half a dozen breadboards before being plugged into sockets soldered to handwired perf board. This synth is a one of a kind instrument – no one would want to build this thing twice.

Additional features include an Arduino with a MIDI in port sending out CV signals to the analog part of the synth. This thing has everything you would expect from a modern take on an analog synthesizer, and it sounds good, too.

44 thoughts on “A Mess Of Wires Turned Into An Analog Synth


    Is that a challenge?

    1. Directly answering your question: he gets to write about it because he is an editor at Hackaday. As long an article has some depth to it, and this one has in my opinion, then that is all you can expect!

      Second of all: why do you attack the writer of this article, even though he found this marvelous project and shared it with us? I think this project is marvelous because it is one of those crazy builds where someone hacks something together completely from scratch, clearly being very passionate about it.

      So I disagree that it destroys the rep of HaD, instead, thanks Brian, this is a great find.

      You on the other hand, you clearly destroy the reputation of a good commenter.

      1. Some years ago, Jan Östman messed up some threads over at the Mutable Instruments forum as well, making uninformed but acidious and destructive comments, not befriending anyone and luckily leaving after not too a long time.

          1. If you take a look at the comments in the thread Brian linked to about [jan]’s synth, you’ll see that he was just as vitriolic in comments on his own project, turning THAT into a toxic thread just as he did this one.

      1. Go ahead and google “Richard Devine Tim Adams and Tim Adams Chaos Box and Tim Adams Blue Synthesizer. I know there’s a Youtube video on the Blue synth and I think one or two on the stuff Tim Built for Richard Devine and he built stuff for the late Pauline Oliveros and others. I think I still have most of his notebooks put away but would be more than happy to share the with you. Tim passed away way too soon.


    So is the design public? Where’s the plans?

  3. All this talk about a mess of wires – that’s very typical of old-school electronic instruments, even commercially built ones. Ever see the inside of a Hammond B3? Sure, it’s all tied into neat bundes, but the sheer number of wires and solder connections has this beat by an order of magnitude. And yet those were built by the thousands.

    Is that really the best you can come up with, [Brian]?

    1. Jim, the way I interpreted it was that a “mess of wires” is a hackish, exploratory and fun feature of the project :-) I.e. a positive remark. And yes, of course you are right about the old 70’s instruments.

      1. I see your point, [Gösta]. I didn’t catch onto this because my own experience goes the other way – perfectly orderly projects turn into big ‘ol messes of wire over time. This usually isn’t a good thing.

        1. Yeah, I agree, I’ve also seen that :-) Now, if I could find some time and experiment with a string machine prototype, that would be quality life. The Waldorf Streichfett is really good, but it’s digital.

  4. I wish analogue was like VHDL or Verilog!

    Great build, very well thought out to have switches instead of patch leads. I like the decals direct onto wood. It makes me want to learn DSP.

    1. Its all digital in the end (planck constant), and once you realize human ear cant sample ~>20KHz things get very easy, even on something like PEE zero or old tablet.

      Basically this fantastic tangible build can be replaced with $20-30 iPad app (by Moog, Korg or one of hundred other independent artists/creators) and nobody would tell the difference in sound (or even pick the app as better).

    2. I seem to recall, from deep in my “are you sure that’s how it was?” memory, that for a short time someone was making an analog equivalent to an FPGA, i.e., a bunch of op-amps with programmable feedback components and interconnections. This was pre-VHDL and pre-Verilog, though, and I’m not even sure how you would handle that kind of device in a high-level language.

      However, you CAN fully simulate analog synths using Spice. The hard part is getting the actual circuit with all its parasitic capacitance and inductance to act like the simulation. I’ve seen analog circuits that failed completely in high humidity due to leakage current through flux residue, so when as somebody else pointed out, 1 part per thousand isn’t good enough for a 6 octave VCO, I cringe at the very notion of actually doing an analog synth in analog circuitry.

      1. The Cypress PSoC series is like that (also has CPU and other parts) but audio synthesisers normally need lots of discrete components like capacitors and resistors even if you put all the op-amps and routing in a chip.

        I have some of those here somewhere (4200 and 4300). They also have FPGA/CPLD like logic blocks so maybe it’s time to beak open more development kits.

    3. I want to try something like this in FPGA but there are issues. Sure I can use ‘single-bit’ encoding to get audio out of a digital pin. I can do all the signal processing as well. The real issues are the control inputs.

      Someone like me who is tone deaf would probably be OK with quadrature encoders for input but musicians need a very high input resolution because they want an *exact* frequency and close enough is NOT ‘good enough’ for them.

      Using pots would have to be 16-bit ADC to get any resolution and FPGA is cumbersome with ADC and normally needs lots of support components unless I find a way to differentiate an analogue signal against a ‘single-bit’ DAC. Perhaps dual slope conversion would work.

      Dunno, just thoughts, but it would be an interesting challenge to try.

      1. The way we did high-res but low-bandwidth analog inputs back when controls were pots rather than rotary encoders, was by using a single ADC and analog multiplexer chips (4051, 52, 53) to choose among the analog inputs.

  5. I have worked on organs whose wiring makes a B3 harness look simple. Which it really is, till you look at the matrix deep inside the keys.
    Better questions would be, is it 1volt per octave or a linear VCO with the ‘duino doing the “tuning”? What range in octaves? Accurate VCO’s that are exponential are messy to make. Thermal compensated stuff. One part per thousand is not good enough to have it stay in tune regardless of it’s temperament.

  6. Holy cats this thing sounds amazing… Makes me want to get into making synths.

    Didn’t Hack-A-Day have a segment on synths for beginners a long time ago, or am I mis-remembering things?

  7. Old string machines are really interesting beasts. As a kid I was always amazed how fat, eerie and emotional they could sound. From what I gather it’s a huge amount of sqare wave oscillators and ingenious variations of chorus circuits. Turning a mess of wires into a string machine would be a worthy project :-)

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