[sdiy] LFSR digital noise source

rsdio at audiobanshee.com rsdio at audiobanshee.com
Mon Nov 11 00:32:51 CET 2019


It’s not really a complex shift register. All you really need is a set of Exclusive OR gates and a simple shift register of the desired length. If you can’t find a shift register that is long enough for your needs, you can simply cascade shorter shift registers. The only disadvantage of a discrete logic design is size. You can certainly tweak the taps if you have the shift registers and XOR gates as separate components.

Note that Texas Instruments lists their CD4006 product as Active.

http://www.ti.com/product/CD4006B-MIL

Of course, this can be simulated in software, but that seems like serious overkill given how simple the basic gates are. I enjoy using processors for processing, but it’s way more fun to use discrete logic gates for pure logic functions.

No matter which option you choose, I think that the signal conditioning from raw digital to analog would be a critical part of the design considerations.

Brian


On Nov 10, 2019, at 6:41 AM, bbob <fluxmonk at gmail.com> wrote:
> anybody know of a digital noise circuit (similar to th ETI/Ken Stone design, http://www.synthpanel.com/modules/cgs31v10_digital_noise.html) that does not use the out-of-production CD4006?  Seems like you should be able to cobble together a complex shift register like that out of other still-available chips, but i'm not savvy enough on digital logic to do it myself.
> 
> b




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