:) ??? Thanks
It's not a one size fits all question.
Bipolar: Advantages - generally reduces part count, more headroom (-9v to +9v), reference voltage is the lowest impedance source (ground). Disadvantages - requires a charge pump, so extra cost and adds the possibility of negative interaction with other effects via noise (though usually not a problem).
Unipolar - no extra parts required (ie charge pump). Whether or not the lower headroom of a single supply is a "disadvantage" is dependent on what the circuit does.
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
(https://img.auctiva.com/imgdata/2/1/7/1/5/4/webimg/1069112504_o.jpg)