The second main element in the workings of HDMI is the connector. Small and durable, the HDMI connector saves much valuable real estate on ever-shrinking AV devices, whilst preserving the essential contact it needs to transfer such a large amount of data reliably.

Did you know that there are actually three different types of HDMI connector, all of different size? They are as follows;

• TYPE A - the standard 19 pin version that it now the norm (pictured left: below)
  
• TYPE B - larger 29 pin configuration for dual link bandwidth (cross compatible with DVI-D dual link). Not currently in use, and not anticipated to be introduced, given the recent advances in HDMI 1.3
  
• TYPE C - the latest addition to the HDMI family, this new tiny connector is close to 1/2 the overall size of the common "Type A" connector. This will be the connector of choice for HD portable devices, and is even capable of supporting the new HDMI 1.3 specification (pictured right: below)

What are all the pins for?

The pins are numbered from the top left as number 1, then lower left as 2, then alternating accordingly through to pin 19 on the lower right. You will see that pin 14 in empty, being reserved for undisclosed potential in future. As for what each of the other things do - TMDS, CEC, DDC etc, check out the "Technology - Bitstream" page for more info (if you haven't already!). There are also two separate non-bitstream pins, being "+5V DC" and "Hot Plug Detect".

• +5V DC This can be used for many applications, such as a low voltage trigger, or more commonly for powering in-line active devices such as signal repeaters.
  
• Hot Plug Detect - This pin simply indicates whether a device, and hence the HDMI line, is active. This is used most commonly to show the status of a HDMI connection, such as on a HDMI distribution amplifier, where the connected outputs may be indicated with a lit LED.

Construction

As can be seen in the "Technology - Versions" section of this site, there was a steady progression of the HDMI format as it was upgraded and refined over the last few years. These refinements saw the introduction of various standards from 1.0 through to 1.2a, and then 1.3. Most of the changes from 1.1 to 1.2a were to do with the construction and termination of the connector. The best HDMI enabled devices, cables and accessories should have connectors which have been individually bandwidth tested, had all pins properly aligned, and have been terminated to comply with at least HDMI specification 1.1.

The stringent HDMI specfication is in place to ensure that the buying public get what they expect, meaning that HDMI Adopter companies should only produce goods of which comply fully to these standards. Anything less will mean that a HDMI system does not work properly - remember that it takes only one weak link in the chain for it to fail!

The bottom line - buy only from verifiable HDMI Adopter brands and/or manufacturers. We sound like a broken record here, but it is very important!

Are Gold Plated Connectors Best?

Gold plating on HDMI connectors, like many other forms of AV connectors, is very common, but is it better? Gold is a fascinating metal as it does not corrode - EVER (you only have to look at the perfectly preserved gold death mask of Pharoah Tutankhamen to see this). However gold is not a particularly good conductor, so it will definitely not improve performance, but it will protect the connector from corrosion. A standard nickel plated connector (the matt grey/silver coloured connectors that you may see on some cheaper gear), being the common alternative to gold plated, may be susceptible to corrosion over time. Gold protects against this, ensuring consistent performance for many years. So, in summary, gold plating enhances longevity.

NEVER ASSUME that gold plated products are generally superior. This may not be the case. A manufacturer may simply choose to spend a little extra on gold plating to make it look 'more expensive', whilst not offering a genuinely great product. In other words, don't buy based only on whether a product's connectors are gold plated or not, but rather on real performance, and if this is too hard to determine, perhaps brand reputation.

Compatibility with DVI-D

As HDMI evolved from DVI-D, it does remain backwards compatible. Fortunately there are no fancy electronics required to make HDMI work with DVI-D, but it is important to note that DVI-D will not support the audio component of HDMI, nor is it compatible with HDMI 1.3. Adapters and adapter cables (DVI-D to HDMI) are readily available in the market.

We've received much feedback to suggest that the HDMI connector should have employed a screw down mechanism, much like DVI. In reality this would have increased its bulk considerably, drawing away many of the intended benefits. Instead the designers opted for a clip-in connector, but evidently some brands clip in better than others. This is another point that's worth checking in-store.

Next Page - HDMI Cable