[Amps] 4 wire 240VAC service? What to do now?

[Commander John]

Ok
I understand about 4 wire 240 vac service.
I installed Code, 10 gauge, 4 wire line to shack and installed a end of line, inline jack. New ameritron amplifier has 3 pin plug on the end. What to do with the safety and ground wires. I twisted the 2 grounds together and installed them in the center pin jack as it was that or cut one off.
Is there a better way?
john W9ZY