MOTM

On Thursday, December 6, 2001, at 06:23 AM, Tkacs, Ken wrote:

>
> If you feed a sine into both inputs of a ring modulator, you get a sine 
> an
> octave higher, not a rectified sine. It outputs the sum and difference
> signals, so the sum of "1" and "1" is "2 (doubled frequency)," and the
> difference is zero. This only works for sines, of course, because any 
> more
> complex signal gets immediately non-linear.
>
> I'm not sure where you're getting the rectification from. You can do 
> some
> rectification with a few diodes, but that's usually used for AC power. 
> For
> audio applications, there're ways of rigging an op-amp to do that, I 
> think.

But isn't a ring mod a four quadrant multiplier? If the input voltage 
at x
and y is both -1, won't the result be 1? So if I had a guitar signal 
into X,
and square wave swinging from +1/-1 at every zero crossing of the guitar
signal, wouldn't that result in rectification? If I do it with a triangle
and square:


X
+1    /\           /\
     /   \        /    \
  0 +------+-----+-------+-------------------------------
            \   /
-1          \/

Y
+1 -------       --------

  0 -------------------------------------------------

-1        -------


Degrees:
0:   0 * 0 = 0
45:  .5 * 1 = 1
90:  1 * 1 = 1
...
225: -.5 * -1 = .5
270: -1 * -1 = 1

Isn't that rectifying the triangle?

Tomy