[Oakleyspatz]

Ok...Lets try and make this simple!

HDMI is a digital connection that can carry both sound and images. It has the ability to carry HD images up to and beyond the current maximum available resolution of 1080p and multi-channel uncompressed PCM which is digital audio that uses no or little compression meaning the audio has better dynamics, better seperation and can attain high frequencies than audio passed through optical or co-axial cables.

The problem many av enthusiasts are finding is that their HD plasma, LCD or projector has only 1 HDMI input and they already have multiple sources such as Sky HD, upscaling DVD, HD DVD and Blu-Ray. This is where the cheaper HDMI amps come into play.
They act as a video switcher only, meaning you can plug a couple of HDMI sources into the amp and have just one cable going to your screen. Then you select the input you want to view on your amp's remote...ergo a video switcher.

The better HDMI equipped amps also have the ability to output up to 8 channels (7.1) of uncompressed PCM (read better) audio from HDMI sources as well. The new HD formats can carry new high resolution audio such as Dolby Digital TrueHD and DTS HD. These uncompressed audio formats are too big to go through optical or co-axial cables and can only be transported via HDMI or 5.1/7.1 analogue cables.

Also the very best HDMI amps can upscale to 1080i/1080p from lower resolution inputs much like some upscaling DVD player can do. So if you connected your 576p PAL DVD player to these amps, they will upscale that image to 1080i for example before sending it to your screen.

Others do something which sounds similar but is different and that is upconvert. Upconversion does not increase the resolution of the image, but rather the quality of the method of transport. For example, if you connected a DVD player via S-Video, the amp will upconvert that signal to HDMI and allow you to then send it to your screen. This results in a much better image especially over long cable lengths.

HDMI v1.3 is the latest incarnation of HDMI and whereas previous HDMI versions can only carry LPCM (uncompressed Linear PCM) which means the conversion of the raw Dolby TrueHD or DTS HD bitstream to PCM has to occur in the player, v1.3 can carry that raw bitstream directly to a compatible amp. How much of an advantage this is remains to be seen once compatible amps start to hit the market. The other advantage v1.3 has is in video colour. It can carry many more colour hues than previous HDMI versions again with a compatible screen.

To be honest, I think HDMI v1.3 is more hype than help and with what we have now you can still obtain superb HD audio/images.

So if you wanted to buy a new amp and wanted to hear HD audio, go for one which can output uncompressed PCM, also called LPCM (linear). The cheaper ones can only switch the HDMI images, but cannot output audio from HDMI.
Toshiba's HD DVD players can output 5.1 TrueHD as LPCM through HDMI (even though the format can carry far more channels than 5.1 when required)

The PS3 uses the new HDMI v1.3 but like I said, the benefit of this remains to be seen....

Hope this helps!

Danny