A front-end bidirectional symmetric bipolar outputs (SBOs) <italic>LLC</italic> dc-transformer (DCX) for half bridge class-D audio amplifier (HB-CDAA) system is proposed and studied in this article. The bidirectional SBO <italic>LLC</italic> DCX provides SBOs for the HB-CDAA without producing voltage pumping on the outputs of the SBO <italic>LLC</italic> DCX. The operation of the proposed bidirectional SBO <italic>LLC</italic> DCX is analyzed, and the effects of the HB-CDAA on the operation of its front-end bidirectional SBO <italic>LLC</italic> DCX are studied. Soft switching of the proposed bidirectional SBO <italic>LLC</italic> DCX can be realized both in the positive and negative audio frequency cycles, which improves efficiency of the proposed HB-CDAA system. A 100-W prototype is built up to verify the analysis results. The experimental results show that SBOs are obtained and soft switching of all switches are achieved.