infinity sound system

I have recently purchased a uk 1998 Voyager LE, the cassette player is working but there is no sound. I have used an external speaker and it worked.. could you tell me where the amplifier is located and if there is an inline fuse please.

the amps are on each of the speakers  the little black attachment on the speakers.If u dont get sound from them see if u get power to the amps them self if not then u have a power issue from the relay under the hood called the NBS
Name Brand Speaker relay. that turnes on the power to the amps for each speaker.

Thanks for your help but, could you please tell me exactly where the nsb relay is?

its in the front fuse box called NBS relay  it will be black