If you want to try a higher voltage with your pedals, try this simple and easy voltage doubler circuit which uses an ICL7660 CMOS Voltage Converter Chip I have found that JFETs such as the J201 sound much better at 18V than they do at 9V with more clean to distorted headroom. Op amps should have more room to "breathe" before distorting and you may just find that an old circuit has new life.

Here is the psuedo schematic which shows the pin connections when looking at the back of the chip. The diodes are silicon 1N4148, the 10uF cap should be 25V or better.

9 volt+ below is the battery PLUS terminal. The battery negative connects to the converter ground. The ring of a stereo input jack (that normally is connected to batter ground) is now connected to the base of a PNP transistor through a 6.8K resistor. The collector goes to the converter V+ in pin. The ground of the converter connects to your circuit ground.

As the picture shows, you need to shield your input wires or else you might get a "whine" in your pedal signal. Make sure that your caps are spec'ed out to at least handle 18VDC.

Thanks to R.G. Keen for the transistor switching circuit. It works perfectly!