By using two isolated outlets the Stack Flex gives you the sum of voltages of the two outlets used. Stack Flex type 1 is fitted with a black 5,5/2,1 mm center negative DC plug (also called the BOSS standard) at the pedal end. If your power supply doesn’t have a dedicated 18 V outlet you can use Stack Flex type 1 to power an 18 V pedal using two isolated 9 V outlets. Most common 18 V pedals are those from MXR, Pigtronix, some wah pedals and drives like OCD which accepts higher voltage than 9 V.

Please note that the Stack Flex makes a series connection of the two outlets used. These two outlets must be isolated from each other. You get the sum of voltages (V) and not the current (mA). If you use it with two 9 V outlets with a 100 mA rating each you’ll get 18 V and still a max. current of 100 mA. If you use it with two 9 V outlets with 200 mA each you’ll get 18 V and max. 200 mA. If you use it with two outlets rated to max. 200 mA both set to 12 V you’ll get 24 V and still max. 200 mA.