When using my Jim Dunlop Power Brick it is causing a lot of background interference noise powering any pedals I use. The signal path is seriously affected. I now know that the power supply is causing the problem as I discovered it when silent practising using my Boss Micro BR. At first I thought it might be cables but they are no problem.
I've tested everything individually with a different power unit and batteries and everything is clean. When I use the DC-Brick it causes mega interference, like using tons of treble and gain without a noise gate; on clean settings. There is also a hell load of interference using my 18V unit pedals, with a constant, harsh sort of humming in the background. I use a MXR Smart Gate and that is ok for cleaning up the hisses of high gain, but there is something affecting the signal that can't be cleared, as when I hook up the Smart Gate alone and turn it on there is interference.
Anyone got any clues on what may be causing this and why ? I spent £99 on a unit I thought was the best quality on the market, and actually thought my setup would sound cleaner due to the improved uses of the electric currents passed out.

Pedals: Boss AC-2, CE-5, LS-2, PH-3, BF-3, MT-2; MXR DoubleShot Distortion, Dime Distortion, 6 Band EQ, Smart Gate, Jim Dunlop Crybaby From Hell DB-01