GROUNDING OF PRO AUDIO: I saw your video on Understanding Grounding in Audio, very good, and I understand the principle of the electricity going back

[Graham Hinton]

a] I'm not sure what video we are referencing?
b] I'm not sure what Bill Whitlock wrote about 'bus bars'?

c] Static electricity is only AC when it arcs. And the the frequency can be up to the Megahertz range.

Static tingling is not MHz.

Parasitic capacitance is charged every half mains cycle by PSUs. This can result in floating at a high DC voltage if there is no discharge path or a double mains frequency if it is completely discharged every half cycle. Without a discharge path to mains Earth damage can occur to circuitry when a connection is made to other earthed equipment. Sometimes this may be a large audible pop, sometimes semiconductors may be damaged.