◊ PCB Documentation

Looney Board

LooneyBoard #1 is the first in a series of PCB boards aimed at SDIY and noise musicians.

This project originated in a series of workshops I've presented, based heavily on Nic Collins Hardware Hacking book and other net resources:

In those workshops, we built circuits on solderless breadboards. Those work great for experimenting, but are a little too delicate for gigging. The LooneyBoards provide an easy way to transfer your designs to an easy-to-build, reliable platform.

LooneyBoard#1 supports: 6 oscillators based on a 40106; 4 more gated oscillators on a 4093; a digital ringmod using a 4011 or similar, and an LM386 audio amp... plus some utility mixer arrays and a prototyping area. See below for details about each section. I'm also working on documenting specific projects you can build with these boards... more to come!

This is the first of at least 2 "voice" boards; we're also working on a "sequency" board and a "modifier" (filter) board. They can be used individually or in combinations to create a wide variety of sound-producing instruments or effects boxes.

PCBs are $15.00 @ — ORDER HERE


The LoonyBoard 1 includes several powered circuits based on CMOS chips, plus some additional utilities.  These circuits can be built separately or combined as building blocks for complex sound/noise devices:

  • Hex Oscillator—6 simple oscillators built using a 40106 hex inverter chip
  • Quad Gated Oscillators—4 oscillators with switching inputs, using the 4093 quad nand gate
  • "Ring" Modulator—digital effect takes 2 signals in and outputs a related but separate tone
  • Amplifier—utility amplifier so you can hear the other circuits via a speaker
  • Mixers—three passive circuits, each of which can mix 4 signals together into one
  • Prototyping area—space to add your own outboard components


IMPORTANT: YOU HAVE TO CONNECT POWER TO EACH MODULE IN ORDER FOR THEM TO WORK.  Each of the four powered circuits on the board has its own power connection (labeled "+Pwr", and circled on the board diagram below).  The board also has a "Power Buss" so you can link all those +Pwr ins to a single 9volt battery.

USUALLY, you'll want to use the Buss to power all the modules from a single battery; it's easier.  To do that, you must CONNECT JUMPERS BETWEEN THE "+Pwr" AND "+Buss" CONNECTIONS NEXT TO EACH MODULE, like this:

Then, you can connect a single battery to the "+9VBuss" and "Gnd" connections on the bottom center of your board.  All of the modules will then powered by the single battery.   On a standard 9v battery clip, the red wire is + and the black wires is – or ground.

There are a couple of reasons why you might choose NOT to connect one of the modules to the common power buss:

  • The amplifier consumes a lot of power.  You might want to put it on its own battery to conserve juice.
  • If either of the oscillators is "power starved" (run on just a volt or two), it'll start to glitch out in unpredictable and perhaps interesting ways... so putting a voltage divider pot between the buss and one of those power ins can be useful
  • You can use the output of an oscillator to provide power to the other oscillator chip... again, producing unpredictable results, sometimes good, sometimes not so... YMMV.

Ground connections are handled on the board, and are common for all modules, even if you use separate power.  

40106 Hex Oscillators

The Hex Oscillator section has 6 identical oscillators built around the 6 inverters of a 40106 chip; each oscillators uses one of the inverters plus 2 resistors and a capacitor.  The resistance/capacitance relationship determines the frequency of each oscillator: smaller resistor/capacitor combinations will give higher pitches; big resistors/caps will be lower.  Typical starting values for audio oscillators might be a 0.1uf capacitor and 100k total resistance.

Each of the oscillators is essentially the same:

Schematic PC Board
40106Oscillator.emf 40106.jpg
  • Space is provided for 2 series resistors (a and b): one is typically a variable resistor to change the frequency of the oscillator, the second one can be use to provide a minimum resistance (running the chip w/ zero resistance can sometimes produce Bad Results). 
    • Total resistance is the sum of both resistors; I often start with 2.2k for one resistor  and a 100k potentiometer (pot)for the other; these values are not critical.
    • Besides pots, there are lots of things to use as variable resistors: photocells; ribbon controllers, force-sensing resistors... or a couple of wires stuck in a glass of tap water and moved back & forth.
  • The capacitor is laid out to support different sizes of caps by providing 2 places to connect one of the sides... use the hole on the outside of the board for one side of the cap, and either of the other 2 for the other lead. 
    • If you’re using an electrolytic cap (useful for really slow oscillators, like for rhythm machines), make sure the negative side goes to ground (hole closest to the outside of the board). 
  • The output of the oscillator is in between the chip and the "b" resistor—the big pad is the one you'll usually use, but I added a second which can be useful if you're adding "touch pads".

4093 Quad Gated Oscillators

The Quad Gated Oscillator section is very similar to the Hex Osc; it  has 4 identical oscillators built around the NAND gates on a 4093 chip, with the same configuration of  2 resistors plus a capacitor per oscillator. 

Schematic PC Board
4093scillator.emf 4093.jpg
  • The difference with the 4093-based oscillators is the presence of an "input", implemented via pins 1, 6, 8, and 13 of the chip (labeled "In1", "In2"etc.).  If the input of an oscillator is high (plus voltage over about 2.2v), the oscillator will turn on; if it is low or tied to ground, it will not oscillate. 
  • If the input is left "floating" (not connected to either power or ground), it may still pick up enough voltage from the circuitry around it to allow some sound to come thru (it can get a little unpredictable, which might be good or bad depending on your perspective). This might be an opportunity to try out touch pads, or an antennae.
  • The outputs are the larger pads towards the center of the chip (near pins 3, 4, 10, and 11). There wasn't enough room to lable them individually, but output 1 is nearest to R101; output 2 is near R102, etc..

4011 "Ring Modulator"

This is kind of a single-purpose circuit; it's not a true ring modulator, but uses digital logic mixing to approximate the classic. 


  • CD4030 or 4070 can be substituted for the 4011. 
  • Inputs can be any square wave signal.  You could try non-square waves as inputs (even external signals boosted via the amp), but YMMV. 

Passive Mixers

These provide a couple simple ways to combine multiple signals.  You can mix multiple Oscillator outputs into one signal... either via a simple resistor network, or through a diode matrix.


  • If the resistors are the same value (I usually use between 47k and 100k), you'll get an even mix of all the input signals. 
  • You could also run each oscillator through a simple volume control before tying them together through the mix network, so you can mix in different levels of each oscillator. 
  • You can tie the outputs of multiple resistor mixers together, if you need to mix more than 4 sources. 
  • The sound of the diode mixing will be considerably different, with more interaction between the mixed signals... this often works better with just a couple of inputs.

386 Amplifier

CMOS circuits will not drive a speaker out directly, so I added a small amplifier based around the LM386 chip.


  • It's not a high-fi amp by any means, but it will let you hear what you're doing. 
  • The default gain of the circuit is about 20x, and the CMOS circuits will overdrive it to distortion; you'll probably want to use the volume control to cut the input level. 
  • There is an optional 10uf capacitor (marked "HiGain Option") you can install to boost the gain to 200x... way too much if you're amplifying the oscillators, but it can be used to amplify an external signal to levels you could use with the CMOS stuff.

Prototyping Area

Empty space for whatever you want.  Three pads on one corner supply power from the buss; three in the other corner provide grounds.  Some possibilities:

  • One more CMOS chip; maybe a 4017 decade counter set up as a sequencer?
  • Use a DIP switch to select different caps on some of the oscillators?
  • Homebrew vactrols (LED/photocell combinations) to provide voltage control of the oscillators
  • Some kind of filter or other sound modifier:

General Tips

  • The oscillator circuits here are pretty standard, but are explored in detail in Nic Collin's wonderful book.  Get it.  Read it. 
  • I always try out designs on solderless breadboards... once I have a configuration I like, then I commit it to a PCB.  The main purpose of these PCBs is to enable you to build custom instruments in a physically "robust" format, so they perform more reliably.  But explore first, then commit your designs to solder.
  • Nothing says you HAVE to use all 10 oscillators, just because they're available.  Sometime less is more, sometimes more is more...

Application Notes:

Among other projects, LooneyBoard1 can be used to build Aurthur Harrison's Cacophonator:


Use the HexOscillator section, but DO NOT link it's power to the Power Buss. The unusual power structure (C5, RV5, R10, C7, and the switches) can be built in the Proto area; also the output resistor/caps on U1E & U1F (R13/14, C10/11--don't omit these... even tho you don't hear them directly, they "wobble" the chip and are an essential part of the sound).