[sdiy] 4006 on evilBay [noise generation]

[Matthew Smith]

Quoth Richie Burnett at 13/02/11 23:55...
> I don't know what the clocking rate is for a typical 15V 4006 PRBS noise 
> generator, but you might be able to get the same noise power in the audible 
> spectrum with a 5V supply just by slowing down the clock speed 
> appropriately.  Slowing the clock rate down essentially spreads the same 
> amount of noise more thickly over a smaller bandwidth.  You just need to 
> make sure you don't slow the clock speed down too far or else you get 
> dulling of the HF and eventually audible colouration (comb filtering) from 
> the sampling process. (It's starts to sound like space invader zaps & 
> explosions.)  Fs=80kHz gives less than 1dB of droop at 20kHz so is a good 
> lower limit for clocking speed.

In which case I will be sure to use a variable frequency oscillator to 
scan the table - possibly just a 555. If the noise generator can be 
tuned to be a Weird Sounds generator for the cost of a pot and possibly 
a switchable capacitor, I'm game!

-- 
Matthew Smith

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