Matrix mixer question

[o_gold]

Hello,
I would like to build a matrix mixer and I've got some questions.
Is it possible to use thishttps://imgur.com/a/EIRosUR Doepfer matrix mixer (works on +-12v) with 9v single supply (+-4.5v with virtual ground)?
my main use will be to mix piezo mics (that already amplified with 386 chip and some 9v guitar pedals.

I see that in Doepfer schematics each voice going through two op amp. Why is that? is it necessary? as opposed to this matrix circuits that seems that each input going through only one op amp http://198.50.113.26/forum/topic-70351.html what will be the difference between the two ?

Thanks for helping!

[GibsonGM]

I think you'll find your clean headroom will be VERY low if you ran on +/- 4.5V!   With the dual supply, you're talking 12V on each side of 0V.    Here, you would only have 4.5V.    If your signal has already been amplified, I think you will experience bad clipping.   I suggest using the recommended power supply....or 2 9V batteries in series (being certain all parts can tolerate 18V)!

There are more simple ways to mix sources...try searching for 'summing amplifier'  or 'opamp mic mixer', perhaps....

Here is a basic version of what I mean.   https://www.allaboutcircuits.com/projects/build-an-audio-mixer/   

hope that helps! And welcome to the forum.

[ElectricDruid]

Welcome!

I agree with Mike that you'll have to think about headroom if you're mixing a few signals and you're only running on 9V. Aside from that, it should work.

The second op-amp is there to re-invert the signal after the inverting mixer so that there is no overall change of phase. It's certainly good practice, but not essential in any way. You could drop the second op-amp and take the outputs from the mixer op-amp directly instead, if you don't care too much about the inversion.

HTH,
Tom

[o_gold]

Thank you very much guys!
What are yo thinking about using icl7660 in order to make +-9v out of a single supply ?