Power supply/psa hum?

skunkwerx

Today after picking up a new pedal, I realised I didnt have enough freakin outputs on the power supply. 

No worries, one output is powering a bright onion mini looper, which is totally passive and the power only serves to activate the led, which is nice but not necessary for it to work. 
Its a strymon zuma supply. 

So firstly before adding the new pedal I unplugged the cable from zuma to the bright onion pedal, and used a spare boss psa to power the bright onions led (when on). 

I plugged the boss psa into the same extension that the zuma and amp is plugged into and got a small hum come through the amp, guitar vol rolled off etc. Regardless of whether the bright onion was on or off. 

So I tried just plugging the boss psa (still powering the bright onion) direct to the wall socket. The same double wall socket that powers the extension with the zuma and amp in. 

Same result. 

So I unplugged the boss psa altogether from both wall and bright onion and plugged the cable from the zumas output back in. Hum gone. All is normal. 

I then unplugged my boss ds-1 from the zuma and tried powering just that pedal from the seperate Boss psa. To see what would happen. Keeping the boss ds-1 off/in bypass the whole time. 
The hum returned but slightly more audible as soon as I connected the seperate Psa to it!  

Its pretty quiet, and actually only noticeable with the gain up and volume up, but still within bedroom levels. 
I believe the katanas built in noise gate which I have on a very gainy channel also killed this hum or hid it. 
But come to think of it, The amp was on high gain, moderate volume, 1watt setting with no noise gate active when I was experimenting and hearing this. 

The zuma alone is as silent as the grave. I thought by using a seperate psa to power something in the same effects chain that it would all play ball as it would be isolated still. But I guess not? 

Or could is be that my ring main upstairs/in this room is just kak?

english_bob

You could use a daisy chain cable to power the looper and the pedal you want to add. 

There's a possibility you end up with a ground loop that way, and get the same hum, but it's worth a try.

ICBM

It sounds like the Boss power supply is the problem. I’ve got one that does it as well, although only with some pedals.

Just daisy-chain a couple of the lowest-draw pedals (one will be the looper) from the same outlet.