A bit of a hand

[the_random_hero]

I've recently thought about putting a piezo pickup system in my acoustic and realised I would need a buffer/pre-amp of some sorts to get things working smoothly. I designed this just this morning and the Multisim models suggest that it will work fine (I haven't included the voltage divider needed to get the necessary voltages to the IC's, but pretend it's there :p).
Any obvious errors I've made? I wasn't TOTALLY sure about if I needed to include a capacitor + pull down resistor between the output of the Baxandall tone controls and the second op-amp, I'm fairly sure I do though for it to bias up properly.

The only last-minute correction I can think of is the gain pot should be 25k, not 5k.

[bioroids]

Are you using bipolar supply to the opamps? If not, the opamp inputs should be refered to Vref (Half of power supply), not to GND. I mean, for example resistor R11, R2, R4 and R7.

You should breadboard this anyway, I don't trust the simulator too much.

Miguel

[PerroGrande]

Miguel is correct.

If you're going to run this circuit from a single voltage supply, you'll need to create a voltage divider ( + bypass cap ) to lift the non-inverting input to the half supply voltage.

I would also put a coupling capacitor immediately on the output of the first buffer stage -- just to the left of R1 on your diagram.

[the_random_hero]

Cheers I was going to use the voltage divider, but couldn't really be bothered adding it to that schematic (it gets too messy). I've updated the schematic and everything still works fine in the simulation, so we'll see how it goes on the breadboard.