Noises Off ( or more accurately, noise’s off)

I have a helmet equipped with an Autcom headset – sadly the Autocom unit is no longer to be found but I figured that all I needed was a 5 pin DIN cable extension and I would be able to connect my helmet to the bike’s 5 pin fly lead. Well, I can but unfortunately it doesn’t really wow me. The volume in the headset is pathetic and the speakers (my lonely pair of front speakers – boohoo) are quite a bit louder. I guess that the missing Autocom unit probably has an amplifier in it but being an electrical nincompoop, I really don’t know if I can do anything short of replacing the headset of buying a new Autocom unit. I really am not keen on the latter option, it seems daft when there is equipment built into the bike for the purpose. All advice gratefully received!