@@ -6,7 +6,7 @@ Stitch Synth is a modular, e-textile, analog synthesizer. That's the most concis
## Synthesizer
It's the last word in the sentence, but probably the most important one: 'synthesizer' is what we've come to call a wide range of musical instrument that 'synthesize' or create sound from electronic signals. In contrast to music made using acoustic instruments, or electronic instruments that use recorded samples of other instruments, with synthesizers we create signals that artificially recreate soundwaves.
It's the last word in the sentence, but probably the most important one: 'synthesizer', or synth for short, is what we've come to call a wide range of musical instrument that 'synthesize' or create sound from electronic signals. In contrast to music made using acoustic instruments, or electronic instruments that use recorded samples of other instruments, with synthesizers we create signals that artificially recreate soundwaves.
There are many many types of synthesizer out there. Just look at how many Legowelt has:
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@@ -75,15 +75,27 @@ Every synthesizer needs an oscillator. An oscillator is a circuit that takes a s
[diagram]
## Wendy: the NOT gate
The heart of the Wendy is a CD40106 IC, which is a logic chip containing 6 inverters / NOT gates.
I strongly recommend that you read Elliot Williams' [Logic Noise blog post](https://hackaday.com/2015/02/04/logic-noise-sweet-sweet-oscillator-sounds/), because it explains the circuit that the Wendy module uses,
In short, the Wendy has a chip at its heart that contains a set of inverters, also called NOT gates. Inverters, to borrow a metaphor from Nicolas Collins in *Handmade Electronic Music*, are like a friend who disagrees with whatever you say - that person who always has to play devil's advocate. Send a high voltage into the inverter, and it outputs a low voltage. Send in a low voltage, and it outputs a high voltage (for the chip we're using, 'high' means 9V, and 'low' means 0V).
The Wendy's oscillator circuit takes the output of the inverter, and sends it back into the input. With the addition of a capacitor and a resistor, this creates a feedback loop that results in an oscillating signal - send this to a speaker, and you have sound! The value of the capacitor roughly determines the range of the pitch you can create, and changing the value of the resistor (or indeed, using a variable resistor) allows you to change the pitch within that range.
Stitch Synth has two oscillators on it:
* One uses a 2.2nF capacitor, and by touching the input and output points of the oscillator, your body becomes the resistor (in general, touching electric circuits isn't advisable, but in this case it's safe - you won't be getting any electric shocks!).
* The second oscillator uses a 10μF capacitor.
[diagram]
mixing
## Delia: the phase-locked loop
The Delia oscillator is a little more complex. Link to Hackaday?
The Delia oscillator uses a chip that's a little more complex than the Wendy. Again I'm going to send you to [Logic Noise](https://hackaday.com/2015/08/07/logic-noise-4046-voltage-controlled-oscillator-part-one/) to properly understand how it works, as Elliot Williams has already done a great job of explaining this.
The Delia module's circuit is exactly the same as the one Logic Noise shows you how to build on a breadboard, and I designed the Anni module to work with it.
# Interactive modules
Four of the modules allow you to play Stitch Synth by touching them. Here's how they work.
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## Volume
Voltage divider
The volume module is a fabric version of a potentiometer, working as a voltage divider, but instead of having a continuous range, it has three settings - low, medium and high.
What this means is...
## Amp
## Hedy
The Hedy module is a simple filter. It's the first step of [this Logic Noise tutorial](https://hackaday.com/2015/03/25/logic-noise-filters-and-drums/) which eventually turns the raw square wave sound of our oscillators into electronic drum sounds! But the Hedy module is simpler than that - using a capacitor, a resistor, and another IC chip, it is a lowpass filter, knocking out some of the higher frequencies of the signal and resulting in a smoother sound.
## Power
The Power module is very simple, but very important! It houses the battery that powers the entire synth. Each module has a power, ground, and signal line, and connecting the power module in between the output of one module and the input of another (not Ada, Anni, Daphne or Maryam, but any of the others) will power everything.
