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Yes that is negative tip.
From what I've been told, the 9v output is important, but even more so the mA rating that is output. It looks like that one is 50 mA. Find out what mA rating the pedal takes and match that as close as you can.
500mA output, the 50mA is the input.
oh and another correction, you don't have to match amperage, you just have to supply as much as the pedal needs, the power supply can be rated for higher amperage just fine. Voltage is what you have to be concerned with.