Pedal board is filling out nicely. I have a one spot power supply with add on that lets you power 8 pedals. Am I able to connect another one of the add ons to it so I can power 15 or 16 total?
Yep. Tally up the amperage (mA) on all the effects, and so long as the total is less than the total output of the One Spot, your good. I think they offer up to 1700mA. Digital effects take a lot of juice, so you usually have to be careful there. But 1700ma can power a lot of analog pedals.
I had 15 pedals on a 1spot once but they were very low draw. Worked great. I now have two 1spots for my 14 pedals.
+1 to adding the amp draw for each of the pedals. If the amp draw is too high and you aren't getting a ground loop, might as well use the one spot + daisy