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Active mixer and 180 degrees out of phase question? Answered

Hello , i want to make a simple active mixer to place in front of the power amp.
I read some documents about active op-amp mixer.And they said :
"Any signal entering the inverting input of the op-amp will appear at the output but it will be 180 degrees out of phase.If the output of the first op-amp were recombined with one of the other signals at a later stage it would cancel out rather than mix. So we have to re-invert the phase with yet another op-amp."
and the schematic should like figure 1 to re-invert the signal .
But if i use the the mixer to direct feed input of power amp , can i use the schematic like figure 2(w/o re-invert the signal) ???

Thanks in advance!
Sorry for my bad English!

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steveastroukBest Answer (author)2012-06-16

You can use your second circuit. You'll get variable phase shifts at low frequencies, if your resistor values are too high, and your C values are too low.

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