Shane's Drivel

HD-DVD impressions, part II November 14, 2007

I’ve got my new Onkyo TX-SR705 up and running. Wow. This receiver has proven to be an outstanding upgrade over my, at the time, high end dolby digital-only Yamaha receiver. And it “only” cost 1/3 of what I paid for that Yamaha long ago. What prompted the upgrade was that the Toshiba A2 HD-DVD player only outputs either 1.5Mbs DTS or multi-channel PCM audio during HD-DVD playback. The 10 year old Yamaha I had supported neither of those.

To get the best possible audio out of a new HD-DVD, or Blu-Ray for that matter, player you need a receiver that supports, at minimum, high-rate DTS. There’s really not a standard I know of that defines what “high rate DTS” is. But I know early generations of DTS-capable receivers are having trouble with this full-bandwidth 1.5Mbps DTS signal that the A2 and other player are putting out.

It is best to have a receiver that supports multi-channel PCM over the HDMI connection. The HDMI cable is beautiful in part because it is one single cable that carries both high def video and digital audio. The A2 can output DTS or multi-channel PCM over the HDMI cable.

The “multi-channel PCM” basically refers to un-encoded digital audio. “Multi-channel PCM” has existed for years, unbeknown to consumers. Inside any garden-variety Dolby Digital receiver, the incoming Dolby Digital encoded bitstream was first decoded into multi-channel PCM and then converted to analog, then amplified and output to the speakers.

With the HD-DVD player and receiver set for multi-channel PCM, the HD-DVD player is doing all the Dolby Digital/DTS/TrueHD/(insert audio format here) decoding and passing un-encoded data straight to the receiver in “multi-channel PCM”. This is the digital equivalent of having a receiver that accepts 6 (5 channels + subwoofer) analog inputs. It is somewhat future-proof in that any new audio format could be handled with a relatively-inexpensive player instead of upgrading the receiver.

How does it sound?

Incredible. I used to think Dolby Digital sounded great. The sound of high def audio formats and DTS audio, even DTS on select standard definition DVDs, is much better than I expected. It is as dramatic as upgrading from beat up, sun-warped cassette tapes to compact discs. The sound just seems infinitely smoother and more natural. There is also a great deal more dynamic range – meaning soft, subtle sounds are quieter while louder sounds are a lot louder.

The surround channels are also a lot more active with DTS/TrueHD,etc than they were with Dolby Digital (I’ve since learned that 5.1 Dolby Digital really only has 3 active channels at any one given time – ouch, what a sham). The result is a feeling of really being surrounded by the movie. Whereas before, Dolby Digital 5.1 mostly used surrounds for gratuitous effects such as something whizzing by, DTS/TrueHD,etc have the surrounds much more involved in ambient sounds that really place you in the middle of the scene. No longer do you have to watch action-packed, stuff-flying-around scenes to feel enveloped with sound. Its great stuff.

I’ve used both the DTS and multi-channel PCM audio output settings. I can’t tell there’s a difference between them. That may change eventually as newer HD-DVDs will have higher bitrate audio which should take full advantage of the TrueHD and other high def audio formats.