Tone circuit with op amp

[DuncanM]

Just to double check, the 10uF capacitor is for shorting AC currents to ground right?

More like stabilizing the "synthetic ground" (Vref) voltage from short term current draw. The capacitor stores charge.

Personally, I'd leave out R3 (that's just me though) and make R4 a bit bigger (3.3k - 4.7k or more) depending how bright you like your LED to be.
Vref to where your earth is now and 0v to the neg supply of the op-amp is getting there.

Also have a look at http://www.runoffgroove.com/tonemender.html as this seems to be what you're trying to do.
Persevere.

[icydash]

Ok cool i'll make those changes, and that runoffgroove circuit really helped, i was actually looking at that to make my power supply circuit and other parts of my circuit, but i'm trying not to copy it exactly...

Vref to where your earth is now and 0v to the neg supply of the op-amp is getting there.

I don't really understand what your saying here ...

thanks!

[icydash]

For some reason in multisim when i make the R3 bigger, like 4.3K, the LED doesn't light up anymore...?

[icydash]

i mean R4.

it's really annoying that you can't go back and edit your posts heh.