i found Nicolas Collins book, Handmade Electronic Music: The Art of Hardware Hacking, on amazon which i highly recomend, and noticed that a lot of the IC’s he uses are similar to the ones I’m playing around with for the video synth.

there is a wealth of information on the net about these types of synthy soundbox thingys, and there’s Ray Wilsons Weird Sound Generator, that uses a single 40106 chip and a handful of other components too, that make up a fantastic starter project for anyone. i built one on a bread board and had a great days fun annoying sal with it…. until she stole the battery.

Lesson 1: Always have more batteries.

so, having built a couple of VCO synth circuits from scratch in the past, i was interested to see how these IC’s would perform, as they are logic Integrated Circuits that range in function from gates and counters to dividers and multiplexers. these chips are used in so many different applications. i had my boiler repaired recently and had a look inside at the pcb and noticed a 40106 that i’m using later on this page.

in the photos above, using just a 74HC14 Schmitt trigger IC, a 100k pot and a capacitor, I built a simple oscillator circuit. Because the chip has six inverters, you can create some horrible drones and chords by building multiple oscillators and feeding them all into one output jack via a summing mixer or just resistors.

The first sample uses a 1uf capacitor, the second, a 0.47uf capacitor.

Audio clip: Adobe Flash Player (version 9 or above) is required to play this audio clip. Download the latest version here. You also need to have JavaScript enabled in your browser.

Audio clip: Adobe Flash Player (version 9 or above) is required to play this audio clip. Download the latest version here. You also need to have JavaScript enabled in your browser.

with the addition of a 4040 counter IC, controlled by the one of the oscillators from the previous experiment, you can create some nice rhythmical sequences by connecting several outputs from the 4040 together.

Audio clip: Adobe Flash Player (version 9 or above) is required to play this audio clip. Download the latest version here. You also need to have JavaScript enabled in your browser.

by moving the pot on the oscillator, the speed of the clock pulses to the 4040 increases.

Audio clip: Adobe Flash Player (version 9 or above) is required to play this audio clip. Download the latest version here. You also need to have JavaScript enabled in your browser.

how to build these things:

i’ll be using 40106 and 4093 IC’s as thats what i have to hand. The 40106 has 6 inverting Schmit Triggers like the 74HC14 i used above, but that IC only works on 5v supplies, hence the arduino in the pictures aboveproviding 5v supply and ground, but from now on i’ll be using a 9v battery and connector because its easier and the 4000 series work on voltages ranging between 3v to 15v-ish. 9v batteries are cheap to find these days in the pund shop and last for ages with these types of circuits if you disconnect them afterwards.

the chips are subject to frying from static electricity discharge from your body, so take some precautions, but to be honest they are hardy little fellows and can take alot of abuse in my experience, but lets not start with bad practises…..

the simple squarewave oscillator

we’ll need:

• bread board
• 9v battery & connector
• hook up wire
• 40106 schmit trigger
• capacitors of various values
• 1meg pot
• 10k pot
• 10k resistor

take your bread board and connect the battery to the power lines. red for positive voltage(9v) and black for ground. insert the 40106 and using jumper wire, connect the power and ground pins to the power buses. on this chip, the positive voltage goes to pin 14, and ground to pin 7.

there are 3 triggers on each side of the chip. connect a capacitor between pin 1 and ground. this capacitor controls the rate range of the oscillator. afterwards, try swapping it to see how it changes, but for the time being the pictures show a 0.1uf cap.

now take a 1meg pot, and connect one side to pin one, and the middle and other side of the pot to pin two of the chip.

then connect pin two of the chip to the positive tip of a mono jack, and the ground bus to the ground shield of the jack, and connect it to what ever you are using to listen to the sounds, make sure you turn it down!!!! these things are loud!

slowly turn up the amp and twist the pot about to create different tones, and bobs yer uncle.

at this point a bit of volume control might be in order, so take the 10k pot and resistor and we’ll make a simple summing mixer/volume control.

remove the jumper cable to the jack from pin two of the chip, and connect pin 3 of the pot to this point. connect pin one of the pot to ground and pin 2 of the pot to somewhere else on the bread board. then take the 10k resistor and connect that to pin 2 of the pot, and the positive tip of the jack to the other side of the resistor.

when the pot is all the way down, the output is connected to ground, so no sound, by rotating it upwards towards pin 3, which is the side connected to the oscillator circuit, it increases the volume.

The final schematic looks like this.

capacitors:

any circuit containing cmos IC’s should use capacitors across the power lines to smooth out any power spikes and fluctuations. these can be 47uf or 100uf, and a 0.1uf.

also, any unused inputs of an IC should be tied to ground, but for bread boarding things i wouldnt worry about it too much.

as i mentioned earlier, by changing the capacitor used in the oscillator circuit, the rate/frequency that the oscillator opperates at will vary. you can use a toggle or rotary switch to change between two different capacitors (or more) giving a different frequency range for each position. for example, a larger capacitor will produce a lower frequency. if you use a 1uf capacitor, the oscillator can produce slow clock pulses like an LFO to drive sequencers or other circuits in circuit bent toys, keyboards and drum machines and produces faster, bassier tones as you rotate the pot.

from here, we still have 5 unused triggers on the IC, so by building another 5 oscillators in the same manner, but changing the capacitors or replacing the pots for LDR, vactrols or any other form of resistance control, you can make a nice wee noise/drone box.

this is where the summing mixer comes in handy, as it saves you having to use a studio mixer to hear the results of all the 6 oscillators. each oscillator output can be connected together at the “audio out” point on the schematic, as the summing mixer on each oscillator passively mixes all 6 outputs together, allowing you to fade each tone in and out to create a cacophony or drones and squeals!!

NAND gate oscillators

you can also use a NAND gate instead of the 40106 schmitt trigger. the 4093 is a quad 2-input schmitt trigger, which has 2 inputs instead of one as on the 40106, and has 4 gates instead of 6 due to the extra input on each.

when using this IC, connect pin 14 to 9v and pin7 to ground.

for the oscillator, pin 1 must be connected to 9v, pin 2 connected to one side of the pot, and a o0.1uf capacitor to ground, and on pin 3, the other side of the pot and then connected to the summing mixer/volume control from above.

the output of this is identical to the circuit using the 40106, however if you connect pin 1 to ground it’ll stop the oscillator. which means you can switch it on and off with the output of another oscillator built from one of the other gates on the IC, which causes some cool sync effects between the 2 oscillators.

more pictures and samples to follow shortly…..