[sdiy] Advices for ringmod and noise source

[Scott Gravenhorst]

Linium <intent at netpratique.fr> wrote:
>Hello,
>
>I would like to know what ring modulator could be nice to build. I found 
>several designs on the net, but i would be happy to hear from you.
>I would prefer a design that sounds meaty or at least with some character :)
>
>The same for the noise source. There are plenty of design, so if someone think 
>one is better than other, i would be happy to try it. In this case, a white 
>is a white isn't it ? 
>

I can't comment on ring modulators (yet), but I like LFSR noise generators, but
you need to use 32 bits or more.  Yes, I know they aren't analog, but analog
noise generators have their own problems.

Pro analog:
o It's analog.

Con analog:
o High gain, high impedance required to amplify the noise.  This amounts to
  hum and radio station pickup being problematic.
o Transistor or diode selection is critical, avoid popcorn noise.

Pro LFSR digital:
o Consistent output, if you replicate the circuit, amplitude and quality will
  be the same for each unit.
o Never have to worry about popcorn noise, or hum or oscillation or radio
  stations from high gain amplifiers.
o No need to select transistors or diodes.
o You can "sweep" the clock frequency for an interesting effect.  No can do
  with analog noise generators, tho you can do something similar with a VCF.

Con LFSR digital:
o The spectrum is not continuous, rather it's a series of lumps, the more bits
  the more lumps, faster clock moves the lumps together.

I cannot perceive the difference between a good analog and a good LFSR digital
noise generator.  For me, it's simpler and easier to make a 32 bit LFSR, which
is enough bits to be considered "good".

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