One of the benefits of using the 9VDC input is that what goes in comes out. If you use a 9VDC power supply you will get 9VDC coming out of each channel. What makes the JUICE JOINT so versatile is that you can input 12VDC/18VDC and 24VDC all up to 2 Amps (2 000mA) and as previously mentioned what goes in comes out. If you use a 12VDC power supply on the input you will get 12VDC on all of the outputs and so on with 18VDC and 24VDC. The OUT/LINK is the 7th output and is exactly the same as the front outputs and can be used to either link to another JUICE JOINT or power a pedal.