Mild Electric Shock When Touching Shunyata Alpha NR Plugs

I got a mild electric shock from a Shunyata Alpha-X NR plug when I accidentally touched it with my fingers after it’s unplugged from the outlet.

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I assume the IEC end of the power cord was plugged into a piece of equipment.

Was the electrical shock possibly a static electricity shock to the ground pin on the plug? 

Electrical power shock? From what to what? From the ground pin to ??? You need a circuit through at least two points through your body to receive and electrical power shock. What was some other part of your body touching at the same time?

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I got a more severe shock when I looked them up on Google. 

Someone will correct me on this but your amplifier stores electricity, often quite a bit, in its power supply capacitors.  So the Amp, not the wall supply,  has probably shocked you.