[sdiy] A query about the TR-909 noise generator

Richie Burnett rburnett at richieburnett.co.uk
Sat Dec 21 12:49:37 CET 2019

---- Tom Wiltshire wrote ----

> I can’t find any references to the two taps they’ve used though - could 13 and 31 be a non-maximal sequence for a 32-stage LFSR? Can anyone confirm this?

I'm not a good enough mathematician to spot an M-sequence polynomial on sight, but you could always simulate it in C or MATLAB or something to determine the sequence length. You know the initial state, so you just need to count the number of iterations before that state comes around again.

FWIW, the 909 noise source is pretty textbook stuff though. It's clocked pretty fast so it's flat out to above 20kHz and the sequence is long enough that you can't hear the repeats even at such a high clock rate. There's not much quirky or interesting going on there, (in my opinion.)


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