Converting existing circuit Boss FA-1 from Unipolar Power to Bipolar Power

[bluelagoon]

I am looking to do the Boss FA-1 circuit only I wanted to do it with a dual rail +9v -9v power supply, or possibly even up to +15v -15v. I just need some education on what changes to the circuit need doing and where exactly the negative volt rail, the positive rail and the 0v needs placing, and also what in particular is now ground reference? is it 0v or -9v The circuit image is shown below. Thanks for any insight and instruction into the matter. Cheers, Trevor

[TFZ]

Bias network can be removed, add filter capacitor for negative rail, use negative supply on opamps, reference JFET input and opamps to ground, connect JFET source to negative supply.