Help identifying amp module

Hi

does anyone recognise this amplifier module? I found it in a Stadium PA amp someone handed in as part exchange, they'd obviously had a go at it themselves.

It would probably be of use as it would appear to be fairly high powered, but i can't find diagrams or any amps that use this end module.

I preume the shielded cable in is audio input, there's also two wires that are fairly obviously audio output, but which two voltages it needs are a mystery. I'll try 5 and 12 as a kill-or-cure, but it's not going to do it any good if i get it wrong.

The pcb is marked as Yamaha, but i haven't seen it in any yamaha amps.

if anyone recognises it please help me out.

Pic1
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Pic4 (with annotation)

cheers, tom d

call yamaha and ask what they put that board in. also did you take it out of a chassis? and if you did what was there for writing on it. it might be someones homemade peice to or a project kit.