Q: I recently bought a new Plasma HDTV and a Samsung BDP-1500 Blu-ray player. My receiver is a 9-year-old Sony without HDMI capability. Would it be wise to buy a new receiver with HDMI audio, or am I OK using my existing receiver?

JASON DeRUSHA, Maple Grove, Minn.

A: Would it be wise to upgrade? Absolutely! Unless you have a very expensive ($600 or more) Blu-ray player with multi-channel analog outputs and internal audio decoding for the new "lossless" audio formats, HDMI is necessary to enjoy the lossless high-definition audio found on Blu-ray.

Audio formats that use lossless compression retain all of the information of the original (nothing is lost). These files aren't as small as those using "lossy" compression, which loses the audio information deemed least important in the original.

You have no idea what you are missing without lossless audio. To get an idea, many readers have commented that when they connect their iPods to their sound systems it does not sound very good. That's because iPods use lossy compression, meaning sound quality is lost as the digital files are made smaller. The Dolby Digital and DTS formats used on DVDs also use lossy compression.

Blu-ray uses either lossless compression or audio that isn't compressed at all, both of which give you a soundtrack that matches the quality of the studio master. You literally can't get any better.

In a modest system the difference will be the equivalent of a nice speaker upgrade, and in high-performance systems you'll shake your head in disbelief.

Most Blu-ray movies have both a high-def audio track and a compressed Dolby Digital or DTS track.

The high-def track is not always selected by default, so before you start the movie enter the setup menu and select the "Languages," "Settings" or "Setup" option. Choose "Dolby TrueHD," "DTS-HD Master Audio," "Uncompressed" or "PCM" to play the best soundtrack.

Different studios use different formats, as listed below.

• Dolby TrueHD: Paramount, DreamWorks, Sony Pictures, Warner Bros., and Disney.

• DTS-HD Master Audio: Fox, Universal, New Line, and occasionally Lionsgate, Paramount and Sony. For example, Sony used DTS-HD MA on "Close Encounters of the Third Kind," since Spielberg has a close relationship with the people at DTS. Fox and Universal use DTS-HD MA exclusively.

• Uncompressed, PCM: Uncompressed and PCM are the same thing and referred to differently depending on the studio, or put together and called Uncompressed PCM. Used a great deal in the past by Sony Pictures and Disney (though both are moving toward TrueHD on new releases) as well as occasional use by Paramount ("Blades of Glory,") Warner Bros. ("300") and Lionsgate ("The Terminator.")

PCM takes up a lot of disc space so the studios are moving toward Dolby TrueHD and DTS-HD Master Audio as they deliver the same results while saving disc capacity. They use compression, but it is lossless compression. Unfortunately older receivers don't decode them and you also need HDMI to transfer the digital track, which is why I recommend you get a new receiver. Two excellent, affordable choices are the Onkyo TX-SR606 and Pioneer VSX-1018HA-K, both of which I will be discussing in an upcoming column.

If you want to try Blu-ray without upgrading your receiver, the compressed tracks on Blu-ray discs are compatible with older digital receivers, but recorded at much higher resolution than they are on DVDs.

They will sound much better than you have experienced before, but not as good as the lossless tracks.