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:

// Veqtor

I came about a Yamaha VSS-200 through our member Removetext, aparently he had one in perfect condition from when he was a kid. ^_^
Eagerly I opened it up, crashed it something like 15 times before i started sending e-mails to lots of people. Piecing toghether lots of information i finally found 14 relativly stable bends on the ram chip, those bends are, to my knowledge exectly the same as those on the VSS-30. So if you are bending one you could check out this tutorial by Kevin Rees. But, that tutorial lacks one important bend, if not two so for those of you who are going to bend it I have these tips to you regarding the ram chip.

It is a 16 pin chip, it is called LH21256 and it is next to the big Yamaha YM2416B. Two pins are dupes, they are relativly useless but have some bends so do make a point for them, they frequently mess the sound up a lot or make the sound stop until its disconnected. The ground point is great because it can give you some pretty cool frequency-doubling and flange effects, so disregard kevins tutorial, the pin marked red on the bottom to the right is ground.

Concerning the other chips: The YM2420, FM-operator, is almost useless to bend, or almost, i did get it to burst out some interesting sounds but in the end i didn’t feel like implementing that bend. I might add it in the future. It is good if you momentarly connect the data control lines toghether, but they need to be reset by connecting A0 to one of the crystal lines. Here is a datasheet for the YM2413 which is almost identical to the 2420, maybe you can find some interesting bends? Please let me know if so.

For the patch-bay I decided to go for banana-jacks because they’re stackable, which means “infinite” multi-bends. Unfortunatly I was dumb enough to think that the plastic above the speaker could stand the stress from drilling so many holes, I did do a quick-fix by putting them in odd places where the plastic wasn’t weak.

In this sound clip i first sample the internal sound sine sweep and then: FIREWORKS! This clip has not been edited at all, so it’s a bit slow, but you get a good sense to feel what bending this thing is like: pure love.

// Veqtor

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:


Me (nitro2k01) and Veqtor found two transparent Gameboys on a flea market a few weeks ago. And is there a better way to rape a transparent Gameboy, than filling it with LEDs? I don’t think so.
Did I say two? Yes, and here’s me and Veqtor with the two ledboys.

Veqtor to the left, and me, nitro2k01, to the right.