[sdiy] Buchla 266 fluctuating voltages

[Scott Gravenhorst]

James Patchell <patchell at cox.net> wrote:
>At 01:38 AM 5/30/2004 -0700, Scott Stites wrote:
>
>         The 5837 is not at all subtle, if you listen directly to its 
>output, you can plainly hear it repeat about every one or two seconds.  And 
>I have a tin ear, I guess you could say, because, in general, I can not 
>tell if audio is being processed in an brand x or y module....they pretty 
>much all sound the same to be...more of less.
>
>         Another alternative, if you need to have pseudo random noise, is 
>to make your own from some HC164 shift registers and a quad xor gate.  32 
>bit long sequences sound pretty white....and the repeat rate is hours....

This is very true.  Someone here, maybe Magnus, pointed out that the spectrum
of LFSR generated noise is a series of lumps and that the more bits you use
(with maximal length taps) the more lumps you get and the faster you clock the
shift register, the closer together they are.  So as you increase the number
of bits and increase the clock, you simulate a continuous spectrum more closely.

Whoever posted this, please do correct me if I'm inaccurate about this.

I have a chart at http://home1.gte.net/res0658s/electronics/LFSRtaps.html that
shows maximal tap arrangements for up to and including 168 bits.  I have found
no data source that goes higher than this.

What I would find interesting is at what number of bits can people no longer
tell the difference between the noise quality of one LFSR and x bits more. 
Eg. is it possible to tell the difference between a 32 bit and a 64 bit LFSR
clocked at the same rate?  Can we safely say that 64 is ridiculous?  I've
built these up to 24 bits and even that sounds very white to my ears (not sure
what metal my ears are made of...).

>
>
>>I didn't use the 5837 - it was a tad too unobtainium for me, and I was
>>a-feared it would come out sounding cyclical.  I've been dying to find out -
>>can you discern a 'heartbeat' using the chip?
>>
>>Cheers,
>>Scott
>
>         -Jim
>***************************************************************
>http://www.oldcrows.net/~patchell
>
>***************************************************************
>
>

---------------------------------------------------------
- Where merit is not rewarded, excellence fades.
- Hydrogen is pointless without solar.
- What good are laws that only lawyers understand?
- The media's credibility should always be questioned.
- The only good terrorist is a dead terrorist.
- Governments do nothing well, save collect taxes.

-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
-- Linux Rex         | RedWebMail by RedStarWare
-- FatMan: home1.gte.net/res0658s/FatMan/
-- NonFatMan: home1.gte.net/res0658s/electronics/
-- Autodidactic Master of Arcane and Hidden Knowledge.