I picked up a used Power Plant Premium (PPP) power regenerator. I have a Zen Mystery Amp (ZMA) from Decware http://www.decware.com/newsite/MYSTERY.html and the ZMA hums mechanically when it is plugged into the PPP. The hum seems to be coming from the transformers or the capacitors. There is no hum coming through the speakers. This tells me the ZMA is not happy and I stopped using the PPP. I have removed all inputs to the PPP except for the ZMA and I still get the hum. I removed all inputs to the ZMA and I still get the hum. I have swapped “premium” power cables with no effect. I have tried Multiwave on and off. No other unit in my system hums when connected that I can tell, but no other unit has such a beefy power supply. This is a tube amp with “a massive power supply with caps so large it is possible to eliminate the choke and any dropping resistors feeding the output stage”. I use a TrippLite i500 isolation transformer and I have no hum at all.