probably a silly question about building a mixer

[madstringbean]

Hi guys,

I wanted to build a mixer and found some schematics here:

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

I appreciated all the explanation but there was one thing that confused me.  Wouldn't an active mixer require a power source?  Like at least a 9v battery or something.  I went ahead and built the mixer (version 3) following the schematic exactly and it doesn't work.  Absolutely no signal passes through it. 

Is this because it needs electricity?  If so, where would I connect the power source?  Or do you think I did something else wrong?  It just seems unlikely that I wouldn't even get at least the slightest buzz passing thrrough if it was only an issue of cold solder joints or something.

Thanks in advance for the help.

Alison

[crochambeau]

Yes, those opamps need power. I would refer to the datasheet of whatever opamp you used and feed it power accordingly.

For mixing, I would use a bipolar supply at close to the rated maximum recommended values (ie: +/-18 as opposed to +/-12) for reason of headroom. UNLESS you've selected the opamp for favourable distortion characteristics...

http://www.eng.yale.edu/ee-labs/morse/compo/sloa058.pdf

Is the goto for tactics to power this if a bipolar supply is unavailable.