Scud Race board into Sega Rally2 cab....audio problem...

Hi.
I was trying to replace my Sega Rally2 model 3 board,with my new Scud Race model 3 board
into my Sega Rally2 cabinet.
All is working perfectly,but not the audio part....
I don't know how to hook up the additional digital audio board that is on the top of the cage
of the scud race board.
Sega Rally doesn't have this additional sound board....
If i connect all the audio cables that i use with Sega Rally2 pcb,i ear all sounds and audio
effects,but someone told me that i cannot use the audio directly into the scud race board
because it's possible that i can damage the board.
So i must connect the digital audio board,but i don't know how...
This are the cable that came out from the audio board


The black one goes into the filterboard of the scud race pcb,but where to connect the grey
cable (the one on the left coming out from connector CN2 on the audio board)????

Is somewhere in the quad audio amp that i must connect the grey cable??


Where????

Plus it's necessary that i connect this cable into the filter board (the one in the red
circle)??


Or i could damage the scud race board??

Please help me if you can.
Thanks all.

In fact, yes it does, but a different model.

Scud runs a DSB1. SR2 runs a DSB2.

The "outer" wiring is different but the inner wiring is the more or less the same. By inner wiring I mean the one you'll find in the metal case of the DSB2. Dont forget to pay attention to the psu cable that is upside down (that can easily be checked by looking at the traces under the pcb). You'll need to remove the connector key so it can fit the DSB1. My advice is to get the filter board and cables from a DSB2, hack them properly, and make them a permanent piece with the DSB1, this way, no errors and plug & play connection.

You have some pictures i can look at??
I really don't understand well what i must do to perform this operation....