Having some time off from school-work has finally let me start working on something I’ve been eager to try out for some time: Building a NES/Atari2600 style noise channel emulation.
Having done some research I found the NES uses Linear Feedback Shift Registers.
I immediatly set out to prototyping one in Reaktor, after 6 hours of intense core-cell coding and swearing, I got a working prototype.
I ended up expanding upon the original idea, by performing a XOR-operation of selectable bits. Next I’m going to add more bits, for a total of 24, and also the possibility of performing a second XOR operation, or perhaps, being able to do AND, OR and NOT as well. We’ll see.
What I want to do now is transfer the code to C++ or Assembler so I can run it on a pic-chip, the ultimate goal being to make it into a eurorack-module, with CV-controlled parameters and pitch!
Here’s six minutes of shift-register glory:
Here we have the second prototype of the Moxibustor glitch oscillator synth. The first prototype had slightly different components, and reminded me of a dub siren in some modes. The second prototype has slightly different components and also a second IC.
What does the Moxibustor do really? It has three knobs and a buttons. Each knob controls the frequency of an astable Schmitt trigger oscillator. The frequency ranges have are different on purpose, so one of the oscillators can go down to down to sub-bass frequencies, and work as an LFO, and one can go up to 1 kHz or so.
The three signals are mixed digitally at the resolution of 1 bit. This clips the three square waves even more, which gives an effect called intermodulation distorsion, which slightly, but not completely, resembles ring modulation. Then there’s also a secondary chip, a decade counter (Just happened to have it lying around :p )
The result is a glitchy thing that offers a variety of glitchy square wave-ish sounds.
But don’t take my word for it, listen for yourself.
If you’re interested in buying a special made piece of this machine, please contact us.
Say hello to OXO’s latest Gadget, the Atari Punk Console. First published as a tutorial on the timer chip NE556 (A dual NE555) in an electronics school book by Forrest Mims III, the APC is worthy its name. The name says it all the fat sounds coming out of this thing really do sound Atari-ish, and the attitude this machine has is really punky!
As the blog GetLoFi points out the APC can easily be extended with body contacts and other experimental conenctions, a piece of advice we made sure to follow.
We made the following modifications to the APC:
Two APC circuits in the same case for added fun.
We replaced the linear potentiometers with logarithmic response ones. This gives a slightly different frequency response curve. The APC has an interesting feature where the frequency does not vary freely, but in steps. And between these steps the frequency pot adjusts the pulse width. Because of the different response, the pulse width modulation gets much more emphasis for low frequencies.
Added LDR (light dependent resistors) to the frequency control, which gives better live control. And when playing on a venue, the light technician is allowed to take part as well. (:
Added body contact! We managed to get a pretty cool FM-like effect, where the wave probably vibrates at 50 Hz when touched. (50 Hz is the frequency used in our electricity plugs in Sweden) This effect is not heard in the sound sample, we’ll be back shortly with more sound samples, using this effect.
Added decay capacitors. What’s this? Well, when testing the circuit at the lab, I saw that when using a wall powered PSU, I got a strange effect turning the PSU off. The frequency slowly decayed, as did the volume, and in the end there was a little hi-frequency tweet. This whole effect was because of the big capacitors in the PSU, which slowly decreased voltage given to the unit. In other words, the capacitor works as a little battery, that dries out in a few seconds. I decided to emulate this effect by putting caps in parallel, giving the same effect. I put different sized caps on the two circuits, to give different decay times. I also added three trig buttons in conjunction to the ono/off switch, trig both, (Which can also be accessed by a foot switch) trig left and trig right, to make the most of the cheapo-style envelope. Also, because of this, I removed the volume pots, as I didn’t see the need any more.
Since this is Veqtor’s unit, he made the design. There is a symbolism in every aspect of the unit, and apart from that, we used old-school knobs for the potentiometers, to get the right feel.
At oxo, we’re starting a tradition to build two pieces of everything, one for me and for Veqtor, which will suit our indivual needs and wishes. My version of the APC will include an analogue sequencer, and body contact areas in the shape of pac-man eating dots. (A coin with a quarter cut off and a couple of screws.)Below is a sound sample of the APC, with the two circuits ring modulated with each other. You can see the passive ring modulator standing behind the APC on the picture above.
The sounds are pretty useful, in fact I can’t hear a single sund that I don’t think can be useful in some situation. Ringmodulating our APC really is a factory for useful sounds. Enjoy:
Dhudmdvjidkf had found this really neat “Lazergun” toy in the trash and handed it to me, I immediatly saw bending potential!
I’ve put an LDR, and a pot in there. It’s got a couple of sounds that are really cool, especially when they begin to self-oscillate.
The ring mod is just two transformers and four germanium diodes.
This is what they sound like in combination with everyones favorite classic, tetris:
About
OXO-Unlimited is a Sweden based electronic music and arts collective.
