We recommend a power supply that provides 9VDC (center negative) at a minimum of 300mA, center-negative polarity.
Do not subject your Strymon pedal to any voltage above 9V. Doing so will damage your pedal and void your warranty.
For further information, please see our blog post on powering your effect pedals at the following link:
Gear Guide: Using the Right Power Supply for your Strymon Pedal