There are two versions of the PH-2: one compatible with the ACA adaptor and another with the PSA adaptor.
*Models vary depending on the voltage in the country/region where they are sold.
You can check which adaptor your PH-2 supports by looking at the label near the DC IN jack or on the bottom of the unit.
*Note: Do not use any adaptor other than the one specified. If you have a PH-2 that requires the ACA adaptor and the adaptor is unavailable, use a 9V battery or power it from an effect unit with a DC OUT jack compatible with the PSA adaptor. Please refer to the related Q&A "Can I Use the PSA Adaptor with BOSS Pedals Specified for the ACA Adaptor?".