[sdiy] Syncable digital noise source.

[Tom Wiltshire]

On 1 Jul 2008, at 13:21, Michael Zacherl wrote:

>
> On Jul 1, 2008, at 1:31 AM, Tom Wiltshire wrote:
>
>> Anyway, since then, I've tried putting a reset input on my PIC  
>> noise source. Then I fed a squarewave from an SH101 into the reset  
>> input. The result was not worth the limited effort, in my opinion.  
>> Whilst the formant-shaping produces noise with certain "flavours",  
>> it didn't produce much that sounded good to my ears. Obviously you  
>> can start the LFSR in many different places and get many different  
>> flavours, so perhaps I didn't explore enough. I wasn't encouraged  
>> to by the results I got. The sound isn't pitched enough to be  
>> really useful, and as unpitched noise goes, pure white or pink  
>> have a smoother quality whilst the synced noise often sounded  
>> "spattery" and uneven.
>
> Hi Tom,
>
>    how about in the LF-range, e.g. when using an S&H and syncing at  
> very slow speeds?
>
> Would it be possible to sort of loop a random pattern?
>
>    :-) Michael.

Yes, it would definitely be possible. The best way would just be to  
use the LFSR to generate random values to feed to a DAC (R-2R  
resistor string or PWM DAC would be enough for this). Generating good  
quality white noise and then reducing it with a sample and hold is  
more stages than are necessary.

If I get a moment, maybe I'll code that up instead and see if I like  
it better!

Tom