As quiet as my previous block (a Rockboard unit) though not as well built. The cables are a littel more flimsy, but it'll do the job. Two points about the design :
The power in is on the front, next to the pedal power outs. This makes plugging it in under a pedal board a bit of a pain.
The unit is slim, but actually too slim. if you want to use the right-angle power jack in your pedal, you have to plug the straight jack into the power supply. But with a Harley Benton spaceship pedal board, the unit is too slim and you'll find it impossible to plug things in and get acces to the power without putting a shim under your pedal board to "raise" the poser supply about a centimetre. Not a deal breaker, but annoying design considerations that should be thought through by Thomann so you can use their products easily together.
So Thomann, please try strapping this unit under a spaceship 40 pedal board directly and you'll see what I mean.
Still works well and at this price point, isolated power at a bargain. I think I'd go with the ROckboard if I was buying again though. Sturdier, with a nice big kettle plug cable.