Need good quality Audio output through LPC21xx controller

We are working on a project based on Vehicle tracking system.In one of
our module we are using audio(voice) for Public transport system.As
if for now we are using filters and a power amplifer We are not able
to get good quality audio output with this setup.

Item used:
Lpc2132 with MMC card interface ,High pass filter+ Low pass filter+
Audio Amplifier+ Speaker

Requirement:


Good Voice quality annoucement system for Public transport System
.

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