Ed’s AV Handbook
Saving the world from poor fidelity
Part 5 More HDMI Tips
HDMI uses 19 pins to move audio and video from point A to B. The pins offer other functions such as the audio return channel (ARC), an Ethernet path, and ‘remote’ control functions. But that bloody ARC feature can drive many AV receivers crazy.
Tip – Go to the TV setup menu and turn ARC off unless you intend to use it.
A single 19 pin interconnecting AV cable is convenient. But the primary purpose of HDMI’s 19 pins is to prevent unauthorized copying. It does this via Transition-Minimized Differential Signaling. TMDS interleaves video, audio, and data via three time controlled digital packets. How this actually works is beyond my pay grade. However AV Pros should be particularly aware of Pin #19. It includes the 5 volt Hot Plug Detect function. This pin carries 5 volts from the source component to the next components’ HDMI sink chip. This is a critical. If the voltage is corrupted the HDMI world stops – no picture, no sound.
Tip – DPL Labs’ Jeff Boccaccio’s rule #1. “Don’t mess with the 5 volts”.
HDMI has problems with cable lengths over 30 feet. The problem can be solved with ‘active’ amplified cables. However some manufacturers rely on Pin #19’s 5 volts to power their cable. That breaks Boccaccio’s rule #1 “Don’t mess with the 5 volts”.
Tip – Install active cables with dedicated power supplies.
HDR bandwidth puts even more stress on Pin #19’s limited voltage. The use of fiber optic cabling can avoid the issue. Reasonable pricing plus easier to use terminating tools have made fiber a feasible choice.
Tip – Research the use of fiber optic cable for long cable run installations.
That concludes part 5. Next Part 6 Ultra-HDTV sources.