I have been planning on building these modules as an independent system to have fun with a Luneta Style Synth.
(got bored at work and made the full set in MS Paint… lol)
Within the Castle Rocktronics website, a full set of 6 Modules are available with Schematics, Perfboard layouts, Panel Drill guides, and full descriptions of the Modules and why/how they work.
Module 000 - PWR
The only module you will use 100% of the time. It’s slightly dishonest to call it a power supply though, as really you use a DC wall-wart as the power supply, this is just a switch, an LED and a bus board.
There is also a general overview of the system, including the colour scheme for the banana jacks and what the general ethos of this DIY project is.
– 4HP
Module 001 - 4x SQUARE
You can’t have a synth, modular or otherwise, without oscillators! But why have one when you can have four? This is a slight twist on popular 40106 oscilator bank, with very simple CV control of the oscillators added with diodes. Very low parts count, a nice easy build.
In the article we cover why it oscillates, as well as why the diode allows for pitch control and gating. On top of that, we figure out how to calculate the pitch of the oscillators and how to figure out where the gating effect of the diode kicks in.
One oscillator being modulated by another
– 18HP
Module 002 - OUTPUT MIXER
The other thing you can’t not have is some way to get the sounds together on one cable and out to an amp or your computer. That’s exactly what this module is for, with a little added extra: built in overdrive! 4 channels that are summed together and stepped down to line-level so you don’t blow anything up & smooth, but gritty overdrive for when you want to get aggressive. Very nice when you have pulsing ambient drones going on.
In the article we cover op-amps as inverting amplifiers (and summing amplifiers), using op-amps on a single-rail power supply as well as decibels and how diodes in an op-amp’s feedback loop create clipping.
Some drones driving the inputs hard to bring out the overdrive.
– 18HP
Module 003 - 4xLFO
Four square wave LFOs with little blinky lights to show you how fast they are going. Endless fun. Just don’t stare into them too long or you will hurt your eyes.
This article is very short as the insides of this module are just the same as 001 – 4xSQUARE, only with bigger capacitors. However, I ran into a few problems while making it, which I write about briefly, mainly to do with drilling and measuring out panels – both of which I ballsed up terribly…
– 12HP
Module 004 - Dual Shift Register
Two deceptively powerful and useful little tools tucked in nice and tight on a small panel. Chain them together for a larger 8-bit register!
The article covers what shift registers actually are, a tiny sampling of their many uses and a look into a circuit building block that we’ll be getting very familiar with – the leading edge detector. There is also what I hope will be the last of my woes from working with acrylic for the front panel.
– 8HP
Module 005 - R-2R
R-2R is two “R-2R ladders” in a tight 6HP package. The four inputs act as a 4-bit digital-to-analogue converter that is perfect for generating stepped waveforms to drive oscillators as a CV source or to create more interesting sounds than the raw squarewaves everything has been putting out till now. It is basically a Digital-to-Analog converter
The article gets really tucked into DC analysis as we pick apart how and why the R-2R ladder works. You will be sick of Ohm’s law by the end of it, but you should also never have to read up about it again!
Shift register into R-2R as it drives one of the 4xSQUARE oscillators
– 6HP
Module 006 - Dual Divider
Another simple double dose module, pretty much just a chip wired up to jacks and LEDs. It is a very useful chip though: the 74HC393. This little guy has two “binary ripple counters” which are sometimes also called frequency dividers.
The article is a brief one, but we talk a bit about the history of the 7400 and 4000 series logic families and some of the things you can use your divider for.
Divider outputs into R-2R, which drives an oscillator for arpeggio-esque patterns. That oscillator is then run through the other divider for a fat 8-bit bass sound.
–8HP
Has anyone had a go at building anything similar?
Are these able to be hooked up to an ADSR and VCA to control the signal?
Links to each Modules PDF are available above!