Got it packed up and addressed. Should get to the PO in the AM, barring disaster.
The hookup is pretty straightforward. Two pads marked "in" and two marked "output". You'll need a 1/8-inch hole in the chassis to mount it, The mount screw provides your RF ground to prevent stray RF from sneaking into the radio from your audio input cable. The mounting post must get bolted to chassis metal.
Might work without it. Never have tried.
The two output pads are easy. One of them gets a wire to C37, the other one a wire to a ground foil near C37. The nearer the better.
You're probably using the "unbalanced" output from the Mbox, the quarter-inch socket. It also has a balanced output. That's the 3-prong socket on the rear. Two of those pins are both "hot" audio, neither one is grounded. The third pin is chassis ground. Best bet for minimum feedback trouble is to use a shielded 2-wire cord plugged into that 3-pin output socket. Don't connect the shield at the radio end. Only the two audio wires, to the two input pads on the isolation board. Of course, the shield should be connected to the ground pin of the 3-pin plug on the Mbox.
Must be getting old. Can't remember which two pins of the 3-pin "XLR" plug are the audio. A continuity test will reveal this. Only one of the three pins on the rear of the Mbox will show continuity to its cabinet ground. The other two pins won't. Those are the two pins your two shielded audio wires should go to.
And if you want to keep it simple and use the quarter-inch "phone" plug with the single shielded wire, that should work just fine. Won't matter which of the two input pins is ground and which gets the center wire.
The idea is to keep "ground" in the Mbox and "ground" in the radio separate, with no direct connection between the two.
73
