Yes, this is a common issue when using multiple displays with different connection types (DisplayPort and HDMI). The issue where the TV "wakes up" your GPU or switches the audio output is usually due to the HDMI connection sending a hot plug detection (HPD) signal to the GPU, even when the TV is off. This can cause the GPU to think the TV is powered on or active, resulting in the switch of audio output.
Here are a few potential causes and solutions:
HDMI-CEC (Consumer Electronics Control): Many TVs have a feature called HDMI-CEC that allows devices to communicate with each other. This can sometimes cause the TV to send signals to the GPU even when off. Try disabling HDMI-CEC in your TV’s settings to see if that prevents the GPU from receiving these signals.
Faulty or Low-Quality HDMI Cable: A poor-quality HDMI cable can sometimes cause false HPD signals. Replacing the HDMI cable with a high-quality, certified cable may help resolve the issue. Look for cables that are HDMI 2.0 or higher certified for better reliability.
Windows Audio Output Settings: Windows can sometimes automatically switch audio output devices when it detects a new display. You can prevent this by setting a default audio output device manually in the sound settings:
Right-click the speaker icon in the system tray.
Select Sounds > Playback.
Choose your desired audio device (e.g., your monitor speakers) and set it as Default Device and Default Communication Device.
Power Management & Sleep Settings: Sometimes the TV or GPU's power management settings can cause this issue. Make sure that the TV is set to a deep sleep mode when turned off, or adjust the power settings in your GPU’s control panel (NVIDIA Control Panel, AMD Radeon Software).
Display Drivers: Updating or rolling back your GPU drivers can also help. Occasionally, new drivers introduce issues with multi-display setups, and rolling back to a stable version may resolve the issue. Alternatively, if you haven't updated drivers in a while, try updating to the latest version.
Disabling Audio Output on the TV: If you never need to use the TV for audio, you can disable the HDMI audio device in Windows Device Manager to prevent it from switching.
Disable the device in sound manager?
Go to Device Manager.
Expand Sound, video, and game controllers.
Right-click the HDMI audio device (associated with your TV) and select Disable.
Custom Resolution Utility (CRU): Some users report success by using the Custom Resolution Utility (CRU) to prevent HDMI hot plug detection. CRU can be used to force certain settings on your displays.
You are on the right track with the HDMI cable theory, but also exploring these other avenues might help resolve the issue. Let me know if any of these steps help!