The SN76477
Is a complex sound generator in the form of a monolithic chip produced by Texas Instruments in 1978. If you played Space Invadors or Sheriff it was this chip that gave you the sound effects.
Being a kid of that time, and one interested in sounds and music, I felt building up a synthesisor around this chip was a good way to learn electronics. This repo is my own private Idaho and hopefully it's of some use to you.
Footprint
The chip is a 28-DIP and has the following measurements:
- 1.78 Mm (0.07 In) Pitch
- 10.16 Mm (0.40 In) Span
- 25.15 X 8.89 X 5.08 Mm Body
Looking inside the chip via an X-ray is cool
I've created an Eagle library of the above, so you can just import it into your project and use it straight away.
Breakout Board
To make this work better with modern bread boards, you need a breakout board in order to connect all the various components up to.
Eventually this will be turned into a fully-fledged PCB
Pin Functions
- Envelope Select (input)
- Ground
- External Noise Clock (input)
- Noise Clock Resistor
- Noise Filter Control Resistor
- Noise Filter Control Capacitor
- Decay Control Resistor
- Attack/Decay Timing Capacitor
- System Enable
- Attack Control Resistor
- Amplitude Control Resistor
- Feedback Resistor
- Audio Output
- VCC
- Envelope Select
- Mixer Select C
- Mixer Select A
- Mixer Select B
- One-Shot Control Resistor
- One-Shot Control Capacitor
- VCO Select
- Super Low Frequency OSC. Control Capacitor
- Super Low Frequency OSC. Control Resistor
- Pitch Control
- VCO Control Resistor
- VCO Control Capacitor
- External VCO Control
- VREG
How The Magic Happens
The SN76477 has the ability to create complex signal waveforms by combining a number of outputs. These outputs (low frequency oscillator and voltage-controlled VCO) added to a selected envelope and manipulating the signals attack, decay, sustain and release (ASDR) results in some beautiful noises.