Re: mixing waveforms... like for a synthesizer

On Fri, 28 Mar 2008 10:50:41 -0700 (PDT), panfilero
<panfilero@xxxxxxxxx> wrote:

This may be a really simple question, but I was wondering what is the
correct way to mix 2 or more waveforms. For example if I want to mix
a sine wave and a sawtooth wave in order to produce an audio tone.
So, lets say I have a sine wave of a a few millivolts and a sawtooth
of about the same amplitude and nearly the same frequency and both of
them are signals which can independently drive a little speaker... but
now I would like to mix the two signal and listen to the resulting
signal. If both of those signals are the outputs of two different
pins or wires... do I just connect the two wires together? I don't
think that's the right way to do it for some reason... but I'm not
sure what is.

Thanks


For linear summing of low-level signals, just use two resistors...


sig1-------R1------------+
|
+-------- output
|
sig2-------R2------------+


R1 = R2 = a few hundred ohms maybe. This would go to an amplifier
input, not directly to a speaker.

Or make a "fader"...


sig1----------------+
|
|
P
O <-------- output
T
|
|
sig2----------------+


using maybe a 1K linear pot. That lets you play with the mix ratio.

John


.

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