[sdiy] Analog Computational Unit

[James Patchell]

At 11:34 PM 1/31/2004 -0400, Shokwave wrote:

>----- Original Message -----
>From: Ryan Williams
>
> >I thought this might make an interesting module but I'm not quite sure how
>to go about using it for audio.  I wonder if anyone has thought of building
>something similar? >After looking around I found the MOTM wavewarper which
>seems to do exactly this. I wonder if it uses the same chip.
>
> >this IC costs about $35 but I figure if it sounds cool then it'd be worth
>it.
>
>Ouch! There's gotta be a cheaper alternative.

There is.  You can pretty easily build one of these by just using an LM3046 
transistor array for the log transistors and your favorite opamp.  You 
should be able to make one that will perform adequately for about $2....


>I *have* been thinking about something along those lines; I was reading the
>appnote for a chip (forget which one right now, it was something fairly
>common) that did x*x/y (fudged with other values) etc. I know that this sort
>of thing can make some excellent DSP waveshaping algorithms...I was thinking
>of deriving squared signal values with it, but was unsure how the squaring
>would work. In DSP stuff, I use signals between -1.0 and +1.0; preserve the
>sign, and the squared signal never clips. If I squash the signal down to a
>max of +-1V, square, then scale back up, will this approach still work? I am
>suspicious of this; it can't be that simple.
>
>-Darren

         -Jim
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