Add, substract, multiply, divide, logic operations ...

[Magnus Danielson]

> > This is really what a mixer does. An addition can easilly be created with an
> 
> mmm .. I don't think that is correct.
> 
> a mixer would 'mix' them together, so that you hear both signals ...
> 
> what I want, is that you ADD each 'value' or step of for example two
> different
> sinoïds and that the result is again *one* completely different waveform
> ...

There is this word that confuses things: mixer

In the audio buisness is a mixer an device which allows for an weigth addition
of a number of signals. Each "channel" will be attenuated or amplified 
according
to user preference and then will the output of each channel be added together.
An channel migth also change the polarity (this will cause the signal to be
subtracted) and there is usually some kind of frequency dependent adjustmens 
(EQ).

In the radio buisness is a mixer an device which will take two input signals 
and
create the sum and difference frequencies of the two frequencies supplied. This
is done througth 4 quadrant multiplying. Some smaller exercise with complex
math and phasor expressions will show the relations quite clearly. It is used 
to
step up and step down the carier signal frequency wise such that the modulation
and demodulation occur at fairly low frequencies (455kHz and 10,7 MHz are 
common) and the tuning will change the other frequency. This is a very usefull
property still today with PLLs and other frequency generation techiques.

In the audio buissness is the radio mixer normally refered to as a 
ringmodulator. This is since you can build an simple 4 quadrant multiplier out
of 6 resistors and 4 diods with the diods mounted in a ring structure.

So, an audio mixer IS addition (or averaging in some cases). If you don't
beleive me I recommend you to try both out and deside for your self. There's
a diodbased ringmodulator at SynthFool. I'd recommend to set a number of in and
output buffers on it even if they are not needed.

Cheers,
Magnus