I need to power circuits that use different voltages at the same time, +/-15v for a stompbox adapter circuit, and +9v for several guitar pedals, and led dB meters. Can I use this power supply splitter with a voltage divider in parallel after the +15v to get +9v, and then wire grounds together? Also, how much current should the 30v dc wall wart be rated for to power everything?
I see no reason why it should not work. You can. Also place a 7809 regulator with a couple of caps on the 15V line. If you use the voltage divider, make sure that the wattage of the resistor is enough to support your load.The wall wart size depends of what you connect. You have to estimate your load, and then go close to double and you will be more than ok
The main possible issue I foresee is ground loops: you will have duplicated grounds through the signal and supply cables, and this can cause problems since the boxes are supposed to be used with floating supplies like batteries or separate wall-warts.
That said, you can always try it and if it doesn't work, you have the option of falling back to another solution
That said, you can always try it and if it doesn't work, you have the option of falling back to another solution