I want to sum the output of 2 Axoloti boards I'm using a little mixer right now but I want something more simple.
I don't need vol pots, so I found in the internet and here on the board some suggestions with opamps, but I could'nt find anything that works with single power supply. I need something that works with 12v rather than +x -x.
Any suggestions?
When I was researching for my project, I was gonna build this:
I ended up using an unused op-amp in my mixer instead. But I asked around in an electronics forum, and a guy who seemed to know what he was talking about said he had really good experiences with FET. He also said I could switch the 2N3819 against BF245 or BF256 (I couldn't find that transistor at my usual place). You'll have to look up if you can run those on 12V though, I don't know. Worst case, just pop a regulator in there i guess?
OK thx! So you used this circuit with an opamp?
I've got some lm386n that I've been trying to use for mixer circuit without succes.
9v or 12v shouldn't matter I think, I've even read that more volt gives you more headroom.
No, I ended up not using this circuit. I already had a dual supply, so I took advantage of that. I used something like this: 
But the one posted before should be good as far as I know.
You can always make a passive mixer that uses no supply at all. The trouble with uni-polar supplies is either you have to use an inverter circuit to make the negative supply, or live with the fact the mixer won't produce a bi-polar output. There are many passive mixer schematics out there. You can easily make one with just resistors and use the gain control on each Axoloti board itself.
Actually with the opamp based circuit I tried I was surprised how good it worked when there was no power (so passive mixing), It summed the outputs pretty well, but it was also like reducing the level on one of them would make the other one louder.
And I want to use simple mixers also to sum different kind of inputs that go into the boards, and also add switches so you can toggle between sending the input to the axos or to the main out.
S for all that stuff learning how to make simple mixer circuits is the way to go I think!
Of course building stuff is the way to go here, but I've had lots of fun with these 5V PAM8403 boards on the RK003 passive mixer (which is the same circuitry as the 'altoids passive resistor' mixer project on instructables) :
Yeah got something like this too but with 10W. Makes a lot of sound and hardly uses any battery 
I mean If I could buy a small active summing board I would be more than happy to buy it it's just that I didn't find anything suitable, so I want to try myself.
Sure:
They came in many different sizes/watts. I use this one with a 5v-->12v step up cable on a mobile 5v powerbank.
