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Here's some circuits to try out - some complete projects, some add-ons - basically, some ideas or starting points. DIY!
& some links down at the end - a selectrion of my favourite places for parts / projects / info / etc...

I've only been dealing with electronics for a few years and I only had a very little formal training. Everything has been picked up from books and the endless wealth of information on the internet. Oh, and by trying things out constantly - be busy! So I'm definitely still learning and making mistakes... Do get in contact if you spot an error in any of these designs or figure out an improvement because these designs are still in quite experimental states.

!NOTE! Please don't go selling anything based on these designs without asking first - I'm reasonable, hopefully you are too!


WorkshopOscMachine
Designed May2008 for use at workshop events
Released as a DIY kit Nov2008

The W.O.M. is now available as a DIY kit from the shop.

Absolutely ALL parts are included - all you need are a few tools (Soldering Iron / Solder / Wire Snippers) - plus full documentation on components, soldering, building and workings! Sonic details are on the SoundDevices page here.

You can download the full documetation here
And the full schematic is here
And there is a thread for Q&A at the Muff Wiggler Forum here


CMOS Designs
Some ideas inspired by the Lunettas Forum at electro-music.com

These simple circuits are meant to be quicky'n'dirty and make use of some of the wide variety of chips available in the 4000 CMOS logic series. The schematics generally just show the simplest possible setup for the chip (check out the datasheets for more info). Its an open ended system for experimentation - either at audio rates (for synthesis) or low freqs (for rhythmic clocking). Please share ideas/pictures/sounds at the electro-music.com forum!

General notes:
- I'm running my system off the +12v supply of my modular setup. CMOS chips have wide power options, so a simple 5v supply would be perfectly adequate and may be more easily intergrated with other modular devices (make sure, though, not to pump negative voltages into the inputs or voltages over the chip's supply voltage). Each schematic shows the power pins for the chip, plus standard stabilizing (eg 100u electro) and decoupling caps (eg 100n ceramic).
- for LED indicators I'm using low-power LEDs which require just 2mA to light. These simply attach to any ouput through a 4k7 current limiting resistor to ground (giving c. 2.5mA)
- all 'in-use' inputs are tied to ground through 100k pull-down resistors. Make sure not to leave any inputs 'hanging' - either tie them high or low (check the datasheets for more details)
- front panel files are made using the good'n'cheap FrontDesigner software version 3.0 from Abacom. All panels are Frac sized. I don't give PCBs for these designs because of their similicity - I've generally just whacked them together on a little bit of stripboard.


4015 Dual 4-stage Shift Register
The 4015 contains two independent 4-stage shift registers and require clock and data signals (along with a reset input which may be implemented or not depending on requirements). I wired the data input with a single-pole-double-throw-centre-off switch so that you can input a logic HI, logic LO or external data flow - in the Up position, the input is tied HI, in the mid position the input is pulled low by the pull-down resistor and in the low position the external input is connected. I also made use of small 5-way rotary switches to give a switchable-select-output - but its hard / expensive to get such switches..

CD4015 at ti.com
FrontDesigner File


4089 Rate Multiplier
The name Multiplier is somewhat confusing - you can think of this chip more as a divider. You set a binary number with the A/B/C/D control inputs and get x/16 output pulses per 16 clock steps dependent on the binary setting. At audio rates this sounds like octave divisions, but the rhythmic effect is quite different as the spacing of the divisions is quite interesting (I should do a demo!). I have done two versions - one with control inputs to the Rate Controls (using SPDT Centre-off switches, similar to the use with the 4015) and one where you just get the switches controlling two 4089s. You get two outputs - one normally low and one inverted.

CD4089 at TI.com
FrontDesigner File (single version)
FrontDesigner File (dual version)


4094 8-stage Serial Shift Register
The 4094 is a very simple 8-stage shift register implementation - just a clock and a data input (same way as for the 4015 -- SPDT C/O switch). You get eight output stages and two complementary serial outputs.

CD4094 at TI.com
FrontDesigner File


40106 Quad-Oscillator + 4077 Quad-XNOR
The 40106 is a great chip to play with - you can make up to 6 simple oscillators from it, but I've chosen to implement simple Syncronization, so only have four Oscs. Each Osc has three rates possible by using a 3way switch. The Sync possibilities use SPDT C/O switches allowing Oscs 2 & 4 to be sync'd to either Osc 1 or Osc 2 (or Sync off).
The 4077 is a quad XNOR gate which gives an effect like ring-modulation (you could also use a 4070 XOR for similar effects).

40106 at TI.com
4077 at TI.com
FrontDesigner File



PCB for Thomas Henry Quadrature Function Generator
- PDF Document with PCB image/ Parts Placement / Schematic

Refer to Scott Stites' TH-QFG webpage for this project.
This is yet another great Thomas Henry design, this time for a four-phase VC(LF)O.


Pattern Generator

I began this 4052 based design as a core for micro-controlled sequencing, but my learning of the micros hit another wall so I thought I'd make a standard modular one to run off my clock divisions.

Should be pretty straight forward - the 4052 is a dual 4 stage multiplexer -- use the two Bit inputs to select which input passes through to the output. So there's four pots (range 0 to +5v) to be selected and the 2nd half of the 4052 is used to provide a step LED indicator.

The bit ports each have two inputs - these are each OR'd together - you could add more.


Electronic (foot)switch
Momentary or Toggling response

This is a simple circuit for an electronic switch - I'd designed this for an external footswitch module but also with a duplicate button panel mounted. There are enough gates spare to easily make a dual version.

Output - 0v to +V Gate (switchable Mom or Tog), plus trigger signal (c. 1ms pulse) each time the button is switched.

The input should be a momentary (normally open) switch to ground.


PCB for Thomas Henry XR2206 VCO - PDF Document with PCB / Parts Placement / Schematic (813kb)

Refer to Scott Stites' XR2206 VCO webpage for this project.

This is a compact PCB for the great XR2206 VCO designed by Thomas Henry.
A lot of functionality and power from a low parts count project.


!Prototype info for personal use only!

The BugCrusher - Audio rate Sample & Hold for Bit Crush effects
Refer to the AD781 Datasheet

I'd wanted to make some sort of bit-crusher effect for ages, but never quite figured the way to use microprocessors or ADC/DACs. And then I came across the Analog Devices AD781 Sample & Hold Amp and it struck me that running this at audio rates would effectively give a simple means of changing the sampling rate - not true bit-crushing but it sounds great!

The AD781 is very easy to implement. All you need is a 5v trigger pulse at whatever rate - this must, however, be of very narrow pulses, so I used a 40106 chip (with 5v supply) to make a narrow pulse osc. You also need to keep the pulses narrow to avoid signal bleed through. From this point I added a Voltage Controlled Resistor onto the circuit to make the Trigger Osc voltage controllable. These circuits were designed for my modular system - they run off a +/- 12v bipolar supply

The 1st circuit is the simple stand-alone - simple & very effective. The 2nd circuit adds voltage control to the 1st circuit (along with some tweaks for the particular application). An LM13700 is used for a floating VC Resistor (resistor values found by trial & error!) and this is driven by a log converter based on a Ray Wilson Music From Outer Space schematic.

I daresay there's some refinements possible - please get in touch if you have ideas on how to make this better.!.

Steven Roeder has done a very compact stripboard layout for the stand-alone BugCrusher circuit - find it here


This is preliminary info - while there's a load of potential in this project, I've always found that wierd (bad) sonic problems occur. I've shelved the project for now, but feel free to make use of the developments.

ISD1416 Lofi Looper with Randomisation
Refer to the ISD1416 datasheet

I first used this chip a few years ago in what I called the Dirty Sampler - great lofidelity looping. The circuit always had a few problems that I just couldn't sort out until I was pointed to the Mobius Trip design at General Guitar Gadgets (thanks to Colin Experimentalists Anonymous).

By using Dean Hazelwanter's analogue front-end I finally overcame the problem of big-assed clicks when you start or stop playback. Great.!. From that point I redid the ISD1416 circuitry a little bit and, with the circuit working pretty well, tried out randomising the playback start point.

The randomisation works as follows: whenever playback is started the states of the 8 address lines are read. So, create a bunch of squarewave oscillators to feed into the address lines and have them all running at different speeds - the sampling of the address on playback therefore appears as a pretty much random number and we get randomised playback. There's things to watch, though - if the 2 high address lines are both high then the chip goes into another mode. In the prototype I've made 6 oscs from a 40106 logic chip and fed these to a variety of address inputs, but always avoiding connecting both of the 2 high lines. This can, though, somewhat limit the range of randomisation - basically, the datasheet says the chip has 160 memory segments. (although I haven't quite figured how the memory is split up because I reckon logically there should be something like 192 possible address combinations.?. anyway, more things to look at.)

So right now the circuit is definitely still in prototype stages. The schematics are a rough guide and the digital board in particular contains a few extra connections for my own test purposes. I daresay there's still a lot of scope for improving some of the component values.

Notes: The ISD1416 needs to be clocked at a speed of somewhere around 1Mhz so a high speed 555 was used. The clocking will no doubt be one of the next areas to hone.


Crackle Box Audio Output
The Crackle Box was originally made by Michel Waisvisz of Steim and I reckon it can really be seen as a pioneering device of circuit bending. There are construction details and a schematic for the cracklebox here (requires the LM709 which is quite hard to find).

I wanted to take an audio output, but things seemed to behave strangely - I initially used a small audio transformer after the transistor amp stage on the original schematic, but this had some problems with ground hum loops (probably due to some incorrect methods.!.). I came back to the circuit a while later and tried a different approach - taking the signal from the output of the LM709, passing it through a simple buffer circuit and then using a transformer for output.

Notes: The input of this circuit is taken from the output pin (pin 6) of the LM709. I used a miniature audio output transformer rated at 20k primary, 1k secondary. The output ground connection is not connected to the circuit's ground and this extra circuit can leech power straight from some point on the main circuit. As with most component values, they can quite probably be changed / improve, but the circuit works for me so...

Links:

This is just a selection of my favourite links (ones I've found particularly useful). There's always going to be loads of other info about that I haven't included, so do carry on searching too...

Synth DIY:
Apache Project - Aaron Cram's synth designs
Bergfotron - Jörgen Bergfors beautiful synth designs
Digisound - site with many Digisound designs which are great starting points for synth DIY
www.electro-music.com Synth DIY Forum - a great place to learn things / ask questions / see good things.
Fonik - great synth DIY with lots of projects and info
Jürgen Haible - ace synth designs
Ken Stone / Cat Girl Synth - supreme site with so many designs and brimming with useful info
Music From Outer Space - Ray Wilson's site is one of the very best. From simple to complex designs, it's all here
PAIA - lots of good project kits and the source of the good-value Fracrak modular frame I use for the bug-modular
Scott Stites - Scott's Old Site - Scotts work is constantly eye opening - really great designs & info
Squarewave Parade - built a version of the BugCrusher (he's got a stripboard layout it) and lots of other interestings
Synthtech - includes datasheets for CEM synth chips

Other Electronics:
Aron Nelson's Stompbox Site - good starting point with loads of schematics and other info
Cloned Analog Gear - many pdfs of old magazine articles on how to build many interesting electronic instruments
General Guitar Gadgets - great and detailed stompbox orientated site
GEOFEX - mainly for stompboxes, good learning resource
Matrix-synth - constant blog of wonder - devices galore
Synapse Magazine - Online from the late 70s, this super magazine has several good circuit articles, a load of musical essays and interviews with people like Terry Riley.

Useful Forums:
Electro-Music - synth DIY. See also the other instrument forums
EM411- circuit bending forum
Experimentalists Anonymous - see also the circuit archive for many designs

Parts Suppliers:
Rapid Electronics (UK) - highly recommended! The very best place for supplies in the UK - cheap and quick delivery (in UK)
Ronlin (UK) - cheapest UK supplier for Press'n'Peel for DIY PCBs
Small Bear (US) - mainly aimed at supplies for guitar pedals, but carry some useful parts (delay chips etc)
Techniks (US) - cheapest bulk supplier of Press'n'Peel for DIY PCBs