Yes. The DVR+ (CM-7500) supports Dolby Digital multichannel audio output (also known as AC-3). It allows you to enjoy great 5.1 channel digital sound when your use the SPDIF optical port to connect to a suitable Dolby Digital AV Receiver. Please note that if a channel is not 'Transmitting' a Dolby Surround signal, it is not possible to receive Dolby Digital.
If you experience 'no audio', reconnect the (CM-7500) DVR+ directly to an HDMI port on your TV to test.