Add, subtract, multiply, divide, logic operations ...

[Magnus Danielson]

> 
> >There is this word that confuses things: mixer
> 
> I've lost track of the players here, but I think what the original poster
> was looking for is best thought of in the digital domain.

OK, to make things clear, here is Bert Schiettecatte's original post:

> Hello...
> 
> just a question ...
> 
> anyone knows how to ADD (literally, no mixing) two signals ?
> (same question for substract, multiply, divide)
> 
> anyone knows how to XOR two signals ?
> (same for NOT, AND, OR, and all other logic operations)
> 
> does anyone have the schematics for this?
> 
> Thanks in advance!
> 
> Bert.

With no strong reference to either analog or digital. However, the request for
schematics (rather than code) indicates to me that he is interested in the
analog versions. If not, what he then need is some example code, but these are
so basic operations in an DSP that he probably would want an DSP introduction
instead. I find the questions more relevant in the analogue domain.
However, I think we should let the original poster clarify that for us. Bert,
can you clarify what you meant?

Have you got any information that where usefull to you?

> eg... You have two sines, one at say 400hz and another at 800hz. He doesn't
> wanna hear the two waves "mixed" together (thus you hearing two tones an
> octave apart), but what he wants is to hear the result of the voltage
> values of the waves being added together at various points in the time domain.
> 
> Hence the potential clarity by looking at the question from a digital point
> of view.
> 
> I'll run whole numbers for ease...
> 
> Take the first wave, and center it on 0v so that you have a + and a - swing
> (ie, no bias). Set a sample frequency, say one value for as fast as I can
> type it, and then you may end up with sample points like this:
> 
> 	-3 -3 -2 -2 -1 -1  0  0 +1 +1 +2 +2 +3 +3
> 
> Now, the second wave may end up looking like this over the same amount of
> time:
> 
> 	-3 -2 -1  0 +1 +2 +3 +2 +1  0 -1 -2 -3 -2
> 
> And, if you *add* these points together you'd get:
> 
> 	 0 -1 -1 -2  0 +1 +3 +2 +2 +1 +1 0 0 +1
> 
> Which is not the same as hearing two tones an octave apart. I think this is
> what he's looking for...

Migth be.... migth be.... I read analogue, you read digital but there is no
major difference in what's done...

Cheers,
Magnus