For most consumer setups you cannot tell a difference when using an HDMI or TOSLINK (optical) cable for your sound system. The major difference with optical cable standards is that they have higher resolution than HDMI cables and can pass formats found on Blu-ray such as Dolby TrueHD or DTS HD Master Audio. However, Optical cables helps to isolate the audio signal from a digital source, eliminates ground Loop Hum, and help to keep the older gear in service such as an old stereo system.