Which wiring is corect for my games amplifier?

[Forrhouse]

I'm wiring a machine from scratch.
I'm currently hooking up an amplifier board
that has a cable with  four wires plugged into it.
This cable at the other end also has only these four wires.
Here is my confusion. On the Inline amplifier side you have
speaker channel A+ going to an analog ground on the games backplane
and you have speaker channel A- going to a regular ground on the games
backplane.  Speaker channel B+ is also going to an analog ground on the
games backplane, while speaker channel B- is going to an analog ground
on the games backplane as well. This makes no sense to me.
I have 2 harnesses that are the same part number and they are both
wired this way. It seem like this is a mistake? If channels
A+ and A- are each going to a ground and channels B+ and B-
are also going to a ground, I would think that you would get no sound out.
Why would they wire these harnesses this way.

The cable diagram has speaker channel A+ going to the left output on the
games backplane and speaker channel B+ going to the right output on the
games backplane. yet, both harnesses are wired as described above.

E~

[Foster]

This is a though, And I only guessing But using my knowledge of the S2000
Can you try a set of S2000 harnesses, one from the top box connector (I am thinking its still at the left rear area) to the amp, and the one from the amp to the speakers.
I might be totally incorrect but its worth a shot.
White with a stripe is the + for that channel and green with matching stripe is - for that channel.
I doubt that IGT changed wire colors and may have even made sure they could use some portions of the S2000 harnesses in the Game King and I Game (I know I would have)