What hums? The amp or the P20?
I would try plugging them to the same high current Duplex top and Bottom not side by side. You obviously have a ground potential difference between duplex outlets creating the hum.
Perhaps one of the high current duplexes was tightened differently regarding green screw torque or its ground pigtail lost multistrand conductors due to poor wire stripping at the factory. Definitely a ground potential issue using same duplex right or left may cure. It is worth a shot.
The other possibility is your two power cords are not matching in ground impedance. I would try two other brands something like two of same Shunyatas The two separate wall outlets if dedicated lines with separate grounds would mask such hum as might using one outlet top and bottom od duplex at the wall.
If the same duplex or different cords don’t cure it there is a ground potential difference in the gryphon.
You would then likely need another P20 hooked to a separate line to address that or use the wall. If both amp power cords are plugged in same wall duplex and different matching power cords don’t resolve it. Then it is an amp issue with internal ground planes.
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I don’t know, it could be those darn Stealth Dream power cords that confuse the P20. It’s time to upgrade them to something better. Wait, I think Al has reached the end of road for the power cords at least this year 
.
Hey Al time to dump those high priced power cables…/.
and get yourself a pair of Pangea AC9SE MkIIs one for P20 to wall
and a second from P20 to your amp…
My P15 and JC5 love them…not all great gear is uber priced stuff…
Give them a try Jay Victor stuff is quite good…so much so don’t feel the
need to look elsewhere…
Best wishes Al
Better yet an excuse for monoblocks or new MBLs since Christmas is nearing.
Whenever I hear a hum in the stereo I just pretend Keith, or Erroll, or Oscar or Thelonious is along for the performance.
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I never have a hum in the stereo but when i’m not listening, I hear these guys anyway.
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I had them plugged into the same high current outlet, top to bottom. It’s not my first day with this gear.
I had the amp plugged into the P20 without hum. But then I moved all the gear to a new location and the P20 hums with the amp connected to it.
No big deal. I’m not interested in any more messing around with it. It’s fine.
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@aangen I would try the P20 into the Duplex the amps like. Then Amps into the P20. Likely loose ground and duplex or in your main service panel wiring. Or if it is not dedicated line some junction box where grounds are shared. That stuff loosens up over time . I had similar monoblock issues before i did new dedicated lines. I was putting seven to eight turns on some connections. Three turns was the norm ging through every main panr connection even the primary main panel bus bars
I have five dedicated 20 amp circuits in the location where my system now lives. I think that should suffice. The gains I am hoping to achieve by plugging the amp into the P20 are not worth any more discussion. I’m out.
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horse dead now.
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Well according to this it takes the right caliber. Database Record Viewer | Horse Side Vet Guide Perhaps Elk can come in and dress the horse like a 
.
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