A look at the TR-909’s noise generator

Posted by & filed under Noise, Roland, Synth DIY, TR-909, Vintage synths.

The TR-909 uses a hardware implementation of an LFSR as its noise generator. We’ve dealt with LFSR noise generators in a few other articles, but we’ve only looked at firmware implementations, so it might be fun to see how the same thing is done in hardware. The circuit is composed of three parts; the shift register itself, a clock, and a start-up circuit. Firstly, here’s the whole thing: Three ICs are used, two 4006 18-stage shift registers, and a 4070 quad-XOR… Read more »