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When to Use SPDIF (Cont’d)

Most home theater receivers have an integrated video switcher. This allows you to connect all sources of audio and video you have at home (cable/satellite box, Blu-Ray player, DVD player, video game console, computer, etc.) to the audio receiver, and the audio and video to be changed from one source to another by just pressing one button or turning a knob. So, instead of having all cables being connected to the TV, they are all connected to your home theater receiver, making it necessary to have only one HDMI cable carrying the video from the receiver to the TV.

Some home theater receivers are able to extract the digital audio from the HDMI connectors from all your audio/video sources. So, you only need to use HDMI cables. See Figure 3 to understand this scenario.

Audio receiver with an integrated video switcher and able to extract digital audioFigure 3: Audio receiver with an integrated video switcher and able to extract digital audio

If your home theater receiver isn’t able to extract audio from the HDMI connectors, then you will be required to use SPDIF cables to carry the digital audio. There are two possible configurations for this scenario. The most common is shown in Figure 4. Instead of having only one cable from each audio/video source, we will now have two: the HDMI cable, carrying the video signal, and the SPDIF cable, carrying the audio signal.

Audio receiver with an integrated video switcher unable to extract digital audioFigure 4: Audio receiver with an integrated video switcher unable to extract digital audio

In the case of computers, if you want to connect only audio, but not video, you can use the connection shown in Figure 4 without using the HDMI connection shown.

The second possibility must be used if your audio receiver doesn’t have a video switcher. In this case, all your audio/video sources are connected directly to the TV, and assuming that your TV is able to extract audio from its HDMI inputs and route it to its SPDIF output, you will use this SPDIF output to connect the TV to the audio receiver. Equipments that only generate audio (e.g., CD players, MiniDisc decks, etc.) must be connected directly to the audio receiver. In this case, the selection of which equipment is going to be used will be done on the TV, not on the audio receiver.

Audio/video sources connected to the TVFigure 5: Audio/video sources connected to the TV

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Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.