Hi gang, hoping you can help me out. I have a tube amp with effect loop. I'm running a few pedals through the loop, but I want to add a few pedals to run direct into the amp as well. I power all the pedals from a single DC Brick power supply. When I plug in the pedals I'm running direct, I get a terrible screeching/hissing sound. So as a test, I borrowed a friend's power supply and used that to power the direct pedals on their own, and the hissing/screeching was gone. Is this my only answer, meaning I have to purchase a second power supply? Or is there something I can do to get a clean signal through a single power supply? Any help would be appreciated, thanks!
The DC Brick isn't isolated, so there's not a lot you can do with just that supply. 

If the only issue is crosstalk between the loop and the direct pedals, something like a One-Spot might solve the problem cheap. If the unit you borrowed isn't isolated, it'll probably be simple to fix, just run each loop off one power supply, even a cheap one. If the borrowed unit was isolated, you may want to experiment with exactly how few isolated pedals you can get away with before the noise creeps back in. Alternatively, you could just get one decent isolated supply and run everything off of that. 
Roc8995 Thanks for the information! I actually didn't even know about isolated / non-isolated options regarding power supplies, so I just learned something. It's not a big deal for me to pick up a 2nd cheapo power supply. I just wanted to be absolutely certain that I couldn't solve the issue with my current unit before I bought I spend any money on another one. Appreciate the feedback!
Last edited by bobbydgo at Aug 11, 2017,
Like quite a few of us, I have several pedals before the amp and several in the effects loop. In the loop I can get away with daisy chaining the power to the pedals but in pedals before the amp, the only way I could stop the noise was to have every pedal on a isolated 9v supply. 

Depends on the amp, but a One Spot would not have fixed the noise issues I was having.