Lunetta Synthesizer 

here is the most recent picture of this system as of May 2012.

and a picture of it with a patch going.

The name Lunetta refers to the retired professional percussionist and musician Stanley Lunetta.   Stan was notable in the area of electronic music and developed very simple circuits often from abusing digital logic integrated circuit chips. More info on Stan here. 

When I began building these 'modules' I really didn't know much of what I was doing.  I was really only aware that I wanted to be able to patch things together to make sounds and that I had decided on banana plugs over standard 1/4" or 1/8" phono plugs, used in many commercial synthesizers, to do this patching.  I had never used a commercial modular synthesizer, and still to this day have not.  I have played and owned several ARP and Moog keyboards, but those never gave me the bug like the concept of a modular.  So with that I set off to learn as I went on developing my own system.   I didn't even really know what this music, that the machine I was haphazardly building, was going to sound like.  I only had an idea of what it would sound like.  What I have found over the last 2+ years of constant building and experimenting, is that the sound is entirely dependent on me and what I put in this machine.  It runs on 9V and draws approximately 700 mA of power.  You will notice that some of these modules have labeling either via label maker or hand written sharpie, but most are blank.  I didn't put a lot of thought into labeling what the controls did, as I never figured anyone would play this instrument but me.  I also liked the raw metal with color knobs and jacks. It took me a bit to adhere to a color code, but now that I have things will go forward more smoothly.  Red jacks = audio outputs, Black jacks = audio inputs.  These color choices when the Lunetta began really were just inputs and outputs, as the signal consideration was very simple.  Mainly logic,  1' and 0's, ons and offs.. but since things have moved beyond the Lunetta simplicity I am just standardizing the entire system of signals for the future.  Yellow jack = Control Voltage trigger inputs, gate inputs, etc...  Orange jack = Control Voltage trigger outputs, gate outputs, etc.. Outputs,, you get it. .  Blue jack = clock signals, Green jack = Ground.  

Power comes in through a jack and goes to a simple distribution board, which then sends power to the  individual modules distro boards.  I used pre-made headers with mates from All Electronics.  They work quite well and makes it easy to plug and unplug each module from power to work on it. 

The Modules

There are many simple oscillators mainly made from CMOS CD40106, 4046, and 4069 IC chips (38 to be exact) about half are for audio range and the other for control range.  They are either Square or Triangle waveforms at the moment.  

There are 12 voltage controlled filters or VCFs.  4 are based on Ray Wilson's Weird Sound Generator, the other 8 are basic Sallen-Key filters with Lo pass, Hi pass, and Band pass inputs.  The voltage control element for these filters is a Vactrol, or an LED (light emitting diode) coupled with an LDR (light dependent resistor)  This allows another waveform, to control certain parameters of other modules, like for instance the cut off frequency of the filters.

There are 12 simple envelope generators which take a trigger or pulse and will output a variable shaped wave of whatever your signal on the input is.

Sequencing elements include 8 digital switches via CD4066.  This allows a switching between 2 events to be turned on or off with a pulse from any of the various clocks or oscillators.  2, 4015 shift registers, 2, 4094 shift registers, 2, 4017 decade counters, 2 4089 rate multipliers, 2, 4024 clock dividers, 2, 4040 clock dividers and 1 master divider module from Ken Stone's CGS.  All of these modules essentially take a clock and or data input and output a varying sequence of pulses to drive other events or to trigger notes to play.

Drums include 4, DS8 clones, 2 bass drums based on the Korg Monotribe, and one snare-ish sounding drum.  

6 simple DAC's or digital to analog converters, these take several inputs and output the sum of those inputs.

Odd balls are a converted Speak and Read toy, an old guitar tuner pedal for tuning individual notes, as well as a Johnson Delay pedal now voltage controllable.

There are 2 mixers, 8 channel and 4 channel mono.

Remember this is a 'simple' system.  Its very caveman-esque.  It can take several patch cables to make even a simple sound.  My approach has been to make soundscapes through multiple 'voices' or patches.  Polyphony is important to me and I make pieces by simply adding voices in one at a time creating each sound to compliment the next until a single voice emerges.



This was the first module I built with the intent of making an all modular synthesizer made up of these simple circuits.  It is simply six 40106 Oscillators, with high and low range switch, coarse tuning knob, output jack and indicator LED.  This module is used as mainly clock signals to drive the various other sequencers, envelope generators, and other triggerable devices.  There was a mistake in my build.. I used 100k pots instead of 1Meg.. this lead to me using unusual capacitor sizes for the timing caps.  See schematic below:

This panel was originaly suppose to be an 8 channel mixer with pan and volume controls and stereo out. At the time this was a very ambitious module and I couldn't get the circuit to work as simple as it was!  I felt a bit defeated and so I salvaged the module as 6 Oscillators with modulation input, Coarse and Fine pots, Square and Triangle out jacks.  The top of the panel I utilized as an extra 4024 divider.  In order to get the triangle loud enough from the 40106, I had to add a simple preamp circuit from Nicolas Collins 'Hand Made Electronic Music' book.  See schematic below.    This was an all points blunder panel.  I used green jacks as the outs instead of my usual 'red' banana jack as out.  This was because at the time I thought about making several systems that each had their own colors, this dematerialized and I was left thinking I should have used red all along.   Additionally the LEDs were unnecessary as the Oscillators are in the audio range and thus 'on' constantly.  Oh well..

This is 6 triangle LFOs or Low Frequency Oscillators built from 3, 4069 Inverter IC chips.  The schematic design is Scott Gravenhorst design.  

A simple-ish envelope generator from Eric Archer.  This takes a trigger signal and outputs an envelope that shapes the input signal.  

This module is, or rather.. was a Johnson Echo/Delay pedal.  I got it off eBay for $35 and thought it was an ok delay considering the price.  However I wasn't using it and thought a delay effect in the synth that could be voltage controlled would be an excellent idea so I set off to modify the pedal for synthesizer use.  It wasn't too difficult really, just swap out the jacks extend some wire for the pots, I added a switch to go between voltage control and the original pot.  The voltage control for repeats and delay is acquired through Vactrols

Here is a bank of 4 VCO from Mark Shaner.  Useful for when being driven by r2r networks.  2 Additional simple square LFO from a 40106.

This is a panel with 4 of Ray Wilson's filter from the Weird Sound Generator.  I got rid of the coarse and fine pots for cutoff and instead added 2 CV inputs via Vactrols for controlling cutoff with other modules.  This was another 'salvaged' panel.  It was previously a square wave shaper, which did very little shaping of any square waves I put into it.. so it became a filter bank.  I used some hand made vactrols, 4N25 opto-couplers as well as a couple VTL5C3's.  It would be a good idea to add a pot as an adjustable voltage divider before going to the Vactrol's LED. This way you would have more control over the level of CV getting to the LED.

Here are 6 more of the same triangle LFO as previously mentioned.

This is 2 individual 4040 binary ripple counters.  These are clock dividers which take a clock signal in and output several different divisions of that clock.  Very nice for sequencing or creating sub octaves.  The circular pattern was improvised and quite eye catching amongst many vertical and horizontaly placed jacks and knobs.  Simply a clock input, and all 12 output divisions available.  

This next panel was a bit of a pain to put together and still has some gremlins running around in it.  What's included?

two identical 4017, 8 step pulse sequencers with clock and reset inputs.

two identical 4015 shift registers with clock and data inputs.

one 4024 divider

two 4011 based ring mod circuits

one R2R ladder

two 4046 VCOs based on Nicolas Collins design from his book Handmade Electronic Music.

this is a module made up of 3 identical resistor to resistor networks.  I actually made 2 of these panels since in the early days I found them so useful.  The inputs are all summed together with the Least Significant Bit at the top and the Most Significant Bit at the bottom.  There are 2 red output jacks.  feed any kind of control voltages into these inputs and it outputs an interesting sum of those voltages, good for driving the 4046 VCOs or any VCO really.  

This is two 4089 rate multiplier chips wired up right to the chip essentially.  

These dual 4094 shift registers provide outputs based on what the clock input speed is, along with the data that is input 'data in' pin of the 4094.  Very interesting patterns can emerge and you can also cascade the last step to the data in of another 4094 for extended patterns.

Another batch of 6 of the same 40106 oscillators with coarse and fine controls, square and triangle outputs, also hi and low range switch.  Schematic is essentially as before. Possibly different values on the range caps.

Also another 6 Envelope Generators.  Same design as before, just 6 more!

The next series of photos are of 2 quad filter panels.  Each has 4 Sallen key filters with vactrol voltage control.  The first has only Lo pass and Hi pass inputs, the 2nd panel has Lo, Hi and Band pass inputs.

Another example of how my color choices changed.  At the time of beginning to add voltage control to some of these circuits, I wanted the CV (control Voltage) input jack to be its own color and purple ended up as the designator for a few modules.  Really just these filters and the envelope generators.

plastic bag to help shield the homeade vactrols from outside light, mainly from the panel LEDs.

closeup of the vactrols

here we have a simple digital switch array.  Using two quad 4066 switches I can turn on and off signals with the pulse out from any of the sequencing modules.  Again we have yellow jacks to represent the connection points to be turned on or off, however later on yellow became known as CV, trigger, or gate  input jacks..

Here is my main Mixer.  This is a 12 input mono mixer with Attenuators for each input, master volume, 1/4" outputs as well as ground connection points.  Circuit was basically straight from Ray Wilson's Ultimate Expander synth mixer.  

Here we have 4 DS8 clones built from PCBs off Marc Bareille's website.  I was planning on adding a trigger pad to the bottom of the panel for each voice.  It has yet to happen with so many things on the list ahead of it.  I added a mixer circuit to have a mix out of all the voices.

closeup of the mixer board

Ken Stone's Master DIvider.  I perf boarded the logic portion of this.  Its essentially the four 4070 XOR chips and the one 4024 divider wired up straight.  Clock input, and reset.  Please visit CGS for the schematic

This is two bass drum circuits cloned from the Korg Monotron.  There is also an additional Snare drum voice courtesy of A. Magic Pulsewave  The two bass drums are at the top, controls are pitch and decay.  The snare voice has a decay control.  For some reason the holes for the LEDs did not end up at 1/4" so the LEDs would not fit in the plastic holders and thus just got wired in place.

This is a unique module.  A Speak & Read salvaged from an old circuit bent project.  I basically just took the PCB out of the plastic housing added the bends and mounted it to a panel for modular use.  This is a very simple bend of just a couple glitches, pitch, and hold button with loop switch.  No CV modulation this is sound output only.  Bend points are referenced from Casper Electronics.  There is a large heatsink on the 7805 voltage regulator added to keep things near the original 6 volts for powering the S&R.  Only heatsink I had.. but it does the job.  

Here is 4 passive attenuators and a banana to 1/4" adapter.  I didn't know how useful these would be until I had them at my disposal.  Very nice for sending adjustable voltages to various CV inputs. Schematic is pretty basic and simple.

This was formerly a Maxon Tuner pedal.  Used for tuning guitar mostly I imagine.  Now it is used to tune my oscillators to actual notes before sending them to a mixer and creating patches with them.  I used a nibbler to remove the metal in a 'square' like fashion.  It got a little chunky and you can only nibble so much with a hand tool.

The final module in this cabinet.  Another Mixer, which was actually the first mono mixer I ever built.  Essentially the same schematic as previous mixer.  I believe 100k resistors were used for the input and for the feedback resistor as opposed to 470k.