I need a very simple mixer

[Lorenzo]

Hi,
I need a simple mixer to mix 2-3 mono lo-fi audio signals.
I need 2-3 line input and the chance to adjust the output volume.
maybe 9v battery...

can you suggest me some schematics?

Actually I made a bodge solding 2 cables in one ouput... it works but...

Thank you!

[PHOBoS]

You might be able to get away with a passive mixer dependig on the level of you signals. Just an attenuator on every input tied together with 1K resistors.
Or you could use the attached schematic for an active mixer. (you can add attenuators on the inputs for level control if you want)

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mixer (single power, virtual ground).gif
Description:	basic single supply mixer
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[Lorenzo]

[PHOBoS]

It should work fine on a 9V battery
(and you can leave out the 100 ohm resistor or better place it before the diode)

[Lorenzo]

thank you so much!

[Dave Kendall]

You might want to check out the TL061 - it uses quite a bit less current than the TL071, at the expense of some slight increase in noise. In practice any extra noise was not noticable in the one I built for a guitarist, and the batteries last a lot longer.

A couple of notes - the Orman circuit uses a 150K resistor in the opamp's feedback loop to give some amplification when the output level is turned up all the way. If you don't need that, then replacing the 150K with a 100K will give unity gain at the output.

The circuit also has an inverted output - this may not be a problem. If it is, then simply use a TL062, and wire the second opamp to the output of the first, before the 10uF cap, with a 100K series resistor into the - input, and a 100K resistor from the output to the - input. Tie the + input of the second opamp to the same point as the + input on the first opamp. This is the classic dual inverting mixer.

cheers,
Dave

[Lorenzo]

[JingleJoe]

I was going to suggest what phobos was saying so I'll add this:

[Lorenzo]

[PHOBoS]

[JingleJoe]

that^ right there is how i do most of my signal mixing, nice depiction phobos you can use different value resistors aswell, to weight the different channels so one input could be louder or quieter

[Lorenzo]

[col2]

Iv'e used Circuit 3 from this site.

http://www.all-electric.com/schematic/simp_mix.gif

works very well!