[sdiy] Pseudo random noise circuits?

Scott Gravenhorst music.maker at gte.net
Fri Sep 17 17:06:39 CEST 2010


Dan Snazelle <subjectivity at hotmail.com> wrote:
>I am trying to find some good digital noise (shift register plus 
>xor) circuits that DON'T use the 4006. 
>
>any help appreciated 

Not sure why 4006 is bad...  but here is a resource:

http://home1.gte.net/res0658s/electronics/LFSRtaps.html

Which gives taps for maximal length LFSR circuits up to 168 bits.

In my opinion, 32 shift register bits should be sufficient to get smooth noise that takes
so long to repeat, you'll never hear it.  Repeat time depends on the number of bits and
the clock rate.

In my FPGA synths where I use noise, I use 64 bit LFSR code, but it's easy to do in an FPGA.

The more bits the better...


>
>Thanks
>
>Sent from my iPhone
>
>On Sep 17, 2010, at 10:26 AM, Oakley Sound <oakleylist at btinternet.com> wrote:
>
>> I built a circuit once that had terrible offset problems. In 
>the end I realised it was down to the bit of veroboard being 
>slightly damp. I had found the board stashed in the back of a 
>cupboard before I had used it and didn't think anything of it. 
>Simply leaving it overnight on the bench was enough to get it 
>working properly. > > It was only later that year when I used 
>some water washable solder that the memory of that particular 
>event came back to me. You see washing the SRBP board with water 
>also didn't do the circuit any good until the board had well and 
>truly dried out. Which took several hours on a warm radiator. > > 
>I now keep all my stripboard sealed up in plastic bags. It keeps 
>the copper shiny too. > > Tony > > www.oakleysound.com > 
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-- ScottG
________________________________________________________________________
-- Scott Gravenhorst
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