HDMI Cable Quality – An Eye for an Eye
There is a lot of “chatter” out in the market about HDMI cable quality. A lot of arguments go “as an HDMI signal is digital it either works or it doesn’t, there is really no difference in cables.” I guess the industry has bought a lot of this on themselves by having crazy ranges in price and by making cables that were engineered for marketing purposes rather than technical performance.
Having sat at the end of a cable production line and also in the HDMI Systems R&D lab, where everyone of our cables is tested, I can certainly tell you that there can be a big difference in cable performance just by doing things slightly differently. Digital cables are tested by using some sophisticated and expensive test equipment. The output is what they call an eye diagram. Here is an example of an eye diagram of an HDMI cable that has passed with flying colors.
HDMI Cable Eye Diagram - Pass
What this diagram is made up of is hundreds of signals displayed one on top of the other. The important things to see here is that the yellow/orange signal lines rise and fall very sharply. This is the typical digital pattern it is either on or it is off, there is little gradation between the two states. Also the lines are closely bunched so each signal only differs slightly. The little blue bar represents a mask and the critical thing is that no signal has hit the mask and there is plenty of room around the mask. This is almost the ideal cable.
Now we slightly changed the construction technique to see if we could degrade the cable just by having “sloppy” construction practices. (Remember this was just a test to prove a point.) We changed some of the secret techniques that HDMI Systems uses to achieve passive equalization of the signal. Here is the resulting eye diagram.
HDMI cable eye diagram - fail
You can clearly see we have lost that “digital” look. The signals vary so much from each other it looks like we have given a five year old a set of crayons to color in. If you look closely at the mask in the left eye you will see that one of the signals has hit it at about 10 o’clock. This cable has clearly failed. All it took was to change a small construction technique. If you used this cable on your HD TV you would see the occasional sparkle, pixelation and jitter. These would be more evident in dark scenes. Depending how good the signal processor is in your TV you may not get anything at all.
So when you read “its digital so it either works or it doesn’t” take it with a grain of salt, with todays advanced digital signal processors, you can still get a picture without having all of the data transmitted adequately, but this picture will be far from perfect.
At HDMI Systems, all of our cables are individually tested, and we include the “eye diagram” test with each cable so you know that you are getting a reliable product and we are confident enough to give it a lifetime guarantee. Next time your are in the market for an HDMI cable ask to see the “eye diagram”. If you are presented with perplexed looks, choose another supplier.
Sam Blacket
Tags: hdmi, hdmi cable, hdmi cables
You can comment below, or link to this permanent URL from your own site.