First a clarification - why PIC? is it really needed?
To me, this looks like a classic radio broadcast problem. A straightforward solution (assuming the PIC is not needed) is to use a FM broadcast unit that you would connect to a TV/audio system and send the broadcast on the FM band.
My reply may be useless if there is a specific purpose to ADC the audio and then transmit via PIC. This however, IMHO, can be very under performing. The audio quality may be un-intelligible. Just off-the-cuff impressions.
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