Green Dungeon Alchemist Laboratories

BATsynth in progress but making a lot of fantastic electronic noise!

The Grand Modular Synth MK1

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Another demo of The Grand Modular Synth MK1, this time in tune! I improvised this tune on a Roland SH09 used only for control voltage (via the exponentiator) so what you hear is solely the VCO and VCF of the grand modular.

Analogue meter driver circuit and formulas (or “how to use old analogue meters in synthesizers”)


I’m a big fan of old analogue voltmeters, ammeters and anything which looks like it came from a russian power plant in 1942. The great thing about these old meters is that many of them are still functional, however, when I started collecting them I had no idea how to use them properly.

Several years and one college course in electronic engineering later, I have almost mastered them; from repairing the mechanics to building driver circuits.

That’s what I’m making this post to share: My analogue meter driver circuit and the associated formulas for adapting it to your meter, because every meter is different! Along with a lot of background information because I find fiddling around with formulas quite confusing despite being good at mathematics.

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In this audio I play poor renditions of video game music with a synthesizer  to demonstrate my “ringmod”, which isn’t really ringmod but sounds somewhat like it and does similar things so I call it “Joe’s Mod”. This is circuit MK3, I’m really happy with how well it’s working. At some points I turn off the modulator signal so you can hear what the un-altered wave sounds like (the first bit of music is un-joe’s-modded).

Important fundamentals of synthesizers

I’ve made a video about this in the past but I want something in text aswell, I want more sources where this information can be found around the internet.

I’m not going to talk about sound or harmonics or fundamental frequencies or waves I’m talking about synthesizers, the machines, because there are some important concepts which seem to be completely missing from standard introductions to synthesizers.

These concepts are the three parts of a synthesizer:

  1. Sound generators
  2. Signal modifiers
  3. Control voltage generators

Sound generators generate an audio frequency signal which you can hear, common waveforms of this signal in synthesizers are saw, square and triangle. These are oscillators, the core of sound synthesis.

Signal modifiers are things like filters, amplifiers and wave-shapers, which alter the waveform to change the sound of the audio signal.

Control voltage generators generate a voltage which controls the other parts of the synthesizer.

A control voltage generator does not make any sound or oscillates below audio frequency so is inaudible but for clicks where the voltage changes sharply. They are things like sequencers, keyboards, envelope generators and LFOs (Low Frequency Oscillators). Control voltage generators are used to control the other two fundamental parts of synthesizers; sound generators and signal modifiers.

Sound generators are usually oscillators and they, along with signal modifiers, are more often than not, voltage controlled. (Hence the names VCO: Voltage Controlled Oscillator, VCF: Voltage Controlled Filter, VCA: Voltage Controlled Amplifier, the list goes on).

Voltage control is the most widely used method of synthesizer control however, one can make circuits which do similar things which are not controlled by a voltage; they are controlled by other means like a variable resistor or capacitor which is changed manually by turning a knob. For example, the humble HCO: Hand controlled oscillator ;).

These are the basics of synthesizers and I wish someone had explained them to me when I started playing synths but these concepts seem to be the last thing on people’s minds when they show someone a synthesizer for the first time or try to explain how synthesizers work. To me, these fundamentals are more enlightening about using synthesizers than anything else I’ve ever read or heard.

Photosynthesizer 1

Some photos show the photosynthesizer without control dials. These were taken during the last parts of construction.

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Demonstration of the photosynthesizer in the light, the lovely blinding sunlight. Can you feel the warm, ultra violet rays DESTROYING your skin?

[insert hissing sounds and recoiling goths]

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This was an attempt to get some deeper sounds out of the Obtruta MK1 in daylight, although it was still overcast so things were a bit more low pass filtered at maximum light levels, which only added to the effect I wanted to produce.

It just occured to me that instead of a VCO or VCF it’s a DCO and DCF: the D stands for Daylight. The ambient light which is determined by the current weather has a direct influence on the sound of this synth. Therefore the sound is closely related to the environment.

A future creation of mine will be the photosynthesizer; a light control based synthesizer which is even more intertwined with the weather and all things which effect ambient light.


As demonstrated by my grandad with assistance on the light controls from myself.
That is my heavily laden workbench you can see around it, where the device itself was constructed with no small amount of difficulty. I don’t think I’ve ever had to troubleshoot anything I’ve made as much as this thing.