Here's what Cioks have to say about the Stack Flex 4:
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 5,5/2,1mm centre negative DC plug also called the BOSS standard at the pedal end. Type 4 is with a green 5,5/2,5mm centre positive DC plug and mainly seen on older EHX pedals for 24V or 40V.
If your power supply doesn’t have a dedicated 18V outlet you can use type 1 Stack Flex to power an 18V pedal using two isolated 9V outlets. Most common 18V pedals are those from MXR, Pigtronix, some Whas and drives like OCD which accepts higher voltage than 9V.
If you have one of the older EHX pedals that need 24V you can use the type 4 Stack Flex with the green DC plug. To get 24V use two isolated outlets in 12V setting. To power one of the three 40V EHX pedals you should use the 18/24 outlet on the CIOKOLATE in 24V setting and the adjustable 4-15V outlet 1 in max. setting at 15V. The pedal will get 39V which is pretty close to the 40V.
If you need to power a pedal with 18 or 24V with a type 2 red DC plug have a look at the Series adapter Flex. If you want only to use one outlet to power an 18 or 24V pedal look at our two Booster Flex types.
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 9V outlets with a 100mA rating each you’ll get 18V and still a max. current of 100mA. If you use it with two 9V outlets with 200mA each you’ll get 18V and max. 200mA. If you use it with two outlets rated to max. 200mA both set to 12V you’ll get 24V and still max. 200mA.
BE CAREFUL when using Stack Flex. There is a risk of damaging one of your 9V pedals by powering it with too high a voltage. Check the specifications of the pedal and if you still have some questions, you’re welcome to send an e-mail to email@example.com and get some useful information.