Circuit Bent NES

In early June I was contacted via email with a request to modify an NES game console for use with chiptunes based music performance. This page is a documentation of my progress from start to finish.

Most of the bends are taken from the 9049A chip that is labelled "sram(vram)". The "schematic" image-003 shows an abstraction of how I sussed out bend points on the NES circuit board. Filled in bubbles on the schematic indicate duplicate points found on the "sram(vram)" chip. The points left open do not effect the video or are unstable (case a crash). The points with dashed above or below them are used as bend points and each is unique. To get the most combinations for the least amount of space, I've chosen rotary style switches. Each switch has 9 positions and 1 pole. Bend points are hooked up to each of the 9 positions and the switch position chooses a point to connect to the pole. By hooking up another 9 positions to another rotary switch and joining its pole to the pole of the other rotary via a toggle switch, the nnumber of possible connections increases exponentially.

The audio reactivity circuitry is built ground up from scratch. It consists of an LM386 and and amplifier/buffer used to boost and buffer the incoming audio. The signal is then passed through a filter bank with allpass (0 degree phase shift), lowpass, bandpass, and highpass filters. Each filter output is passed to a voltage comparator with an adjustable threshold such that when the signal crosses the voltage threshold, the comparator outputs a +5 volt pulse which is the logic equivalent of high or true. This is similar to an overload meter but instead converts the audio to a series of digital pulses. This logic signal is fanned out to two places. First it feeds the base of a 2N3904 NPN transistor which drives an indicator LED (the LED is between the positive voltage rail and the collector, a 1K ohm resistor is between the emitter and ground). Second it feeds the control pin on a 4066 quad bilateral spst switch. The 4066 is basically a chip that contains 4 digitally controlled spst switches and is much faster than, and takes up much less space than 4 reed relays. The gates of the switch are then connected to two bend points on the NES console. Schematics are posted below. I've also gone a step further and used a 4029 counter to control a 4066. As the bass threshold is crossed its signal is fed into the 4029 clock input. The counter then counts up and holds its state until the clock is pulsed again. The counter outputs are feeding the 4066's control pins and the switch gates are tied to different bend points on the NES.

schematics and boards ::

Full Schematic

PCB Trace Layout

Parts Position Guide

parts list

images ::

Manual Mods


Pinout "Bubble Code"

Console + Wires

PCB Acid Bath

PCB Populated + Trimmed

Wiring 50% Complete

Near Complete


Screen Shot

video ::

video-001 - The setup in its early stages
video-002 - Testing the 4066
video-003 - Testing the manual bend section
video-004 - The setup with the audio reactivity circuit hooked up
video-005 - Demo of the audio reactivity circuit
video-006 - Test - 01
video-007 - Test - 02
video-008 - Test - 03