Help with Mini Mixer

[Perrow]

So I built this mini mixer circuit I found on the interwebs a long time ago and drew a layout for just about as long ago, and of course it doesn't work and of course I can't find the source.

Well it's simple enough, four inputs with "standard" volume pots, a inverting opamp (TL071) with a pot as a variable feedback resistor and not much else. So why doesn't it work?

It does work as a passive mixer, but I get no boost what so ever from the opamp. The only thing that changes when I turn the power on/off is that it goes quite for a couple of seconds (until the PS capacitors are drained.



I've found similar circuits and can't find any differences that would explain why this doesn't work.

I've also found my layout for the GGG mixer with a dual opamp and some other nice to have features but I feel like I should be able to get this to work. It'd be everything I need at the moment and I could sell it to my brother whenever I feel like I want something better (or just some money to build other stuff).

[frequencycentral]

and I could sell give it to my brother whenever I feel like I want something better

Fixed that for ya.  

[Perrow]

and I could sell give it to my brother whenever I feel like I want something better

Fixed that for ya.  

Parts cost + a little for the effort, he can afford it.

[slacker]

It won't work because the layout is wrong. Pins 3 and 4 are both connected to ground so the opamp is not biased properly. It needs to be connected to a voltage divider to bias it to half the supply voltage. Look at the GGG mini mixer to see what I mean. Or it could be run off 2 batteries with pin 3 and the bottom of the R3 connected to ground and pin 4 connected to -9 volts.

[Perrow]

It won't work because the layout is wrong. Pins 3 and 4 are both connected to ground so the opamp is not biased properly. It needs to be connected to a voltage divider to bias it to half the supply voltage. Look at the GGG mini mixer to see what I mean. Or it could be run off 2 batteries with pin 3 and the bottom of the R3 connected to ground and pin 4 connected to -9 volts.

That was going to be my next experiment, guess the Dremel will come to use cutting tracks again

[Perrow]

It needs to be connected to a voltage divider to bias it to half the supply voltage.

Indeed it did, thanks for spotting it for me. Still a real noob when it comes to op-amps, but I'm reading up on them and learning more from each mistake