signal ground on X.5 amplifiers

[5spheres]

My speaker cables have an extra connector at the input end for connecting the shield to the amplifier's signal ground. My X.5 amplifiers however don't have a dedicated signal ground post. Can I just connect it to a chassis screw?

 

[Nelson Pass]

Actually X.5 amplifiers have been providing a signal ground
post for quite some time. If you have it, it's the white
5 way on the rear.

😎

 

[5spheres]

signal ground

My X.5's must be one of the earlier units as I don't have the white signal ground... (Though I know what you're talking about Mr. Pass from pictures on the official site.) Is there an alternative?