[sdiy] Random Voltage Generator & ADV/Cookbook

[harry]

OKEY-dokie...

There is merit to using the S/H (LFO) to sample a random noise source...
then lag process (LPF) the result.

Most junction noise sources are severely lacking in real low frequency
amplitude... this is usually from the HPF formed by the blocking cap
in the first stage.

By sampling the wideband noise, you get large voltage variations, which
are easier to LPF....

H^) harry

Scott Gravenhorst wrote:

> xeno at xenoweb.com wrote:
> >Magnus Danielson wrote:
> >>
> >> From: Scott Gravenhorst <music.maker at gte.net>
> >> Subject: Re: [sdiy] Random Voltage Generator & ADV/Cookbook
> >> Date: Sun, 11 Nov 2001 13:27:01
> >>
> >> > A ranodom voltage *is* noise.
> >>
> >> I think he wants slow changes. There is basically two types, just slow
> >> variations, or random steps.
>
> Yes, I'm sorry, I was being a smart-ass.
>
> >Yes! Slow changes/variations are what I'm after, not sample and hold.
> >
> > > The slow variation version is just a lowpassfiltered noise source, if
> >> you vary the lowpass filters frequency, you have more or less of the
> >> quicker movements.
> >
> >So by running a 'regular' white or pink noise source through and LPF and use
> >that to modulate a filter, I'll get the same result?
>
> Yes.
>
> >> The random step version is a noise source with a sample-and-hold
> >> circuit controled by an LFO. As you vary the frequency of the LFO, you
> >> vary the length of each step.
> >
> >Yep, I understand the S&H via LFO (an SH-101 was my first synth) but I'm
> >looking for smooooooth changes. :0)
> >
> >> Both these can use a common noise source, the after-processing is
> >> simple to duplicate.
> >
> >So in a circuit where you can vary the speed of the random voltage,
> >what is happening? Are you simple changing the cutoff frequency of a LPF filter
> >the noise is going through?
>
> You have it.  Depending on just how slow you want to go,
> you may want to have an LPF that can go to very low
> cutoff frequencies.  Subaudio.
>
> >> You DO get noise outputs as a side-effect.
>
> Which is what I was being a smart-ass about...
>
> >> Cheers,
> >> Magnus - contributing to the noise - that must make me a noise generator...
>
> Never.
>
> >:0))
> >
> >Thanks Magnus!
> >--
> >John Greczula
> >_____________________________________________________
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> >
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