Dolby Digital vs. PCM for Best Multi-channel Audio Signal

[420audio]

I have a Time Warner Cable HD cable box that offers the following audio output signal formats: "Dolby Digital", "Stereo" and "PCM." The cable box is connected to my Marantz AV7005 preamp via a digital coaxial cable (and component cable for video). I like to listen to the music channels offered by TWC. So, which audio output format offers the most channels: Dolby Digital or PCM (obviously not Stereo)?

My Marantz seems always to report that the audio signal format is 2/0/.0 )X/Y/.Z where X = front left, front right and center; Y = surround; and Z = the sub woofer channels). If I were getting a 5.1 source format, the Marantz would report 3/2/.1. The signal format of 2/0/.0 is reported by my Marantz when using either the Dolby Digital or PCM signal formats from the TWC cable box. The problem is that with only two channels of source audio (2/0/.0), I cannot utilize a listening mode of, for example, Dolby Digital IIX and thereby actually get 7.1 surround sound out of the Marantz

 

[FirstReflection]

Set the cable box to Dolby Digital output. All the "PCM" output option would do is decode the Dolby Digital audio inside the cable box itself. There's no benefit to this.

The actual number of audio channels (2.0, 5.1, etc) that come out of your cable box depends on what you're watching. Most prime time TV shows on the HD channels will have 5.1 Dolby Digital audio. But many other programs, including the digital music channels, are 2.0 stereo only.

If you're listening to a 2.0 audio program, and you want to expand it to use 5 or 7 speakers, select the Dolby Pro Logic II or Dolby Pro Logic IIx listening mode on your receiver.

 

[M Code]

Time Warner in SoCal broadcasts audio in Dolby Digital, 2.0 (stereo) for certain channels and 5.1 for others (HD & premium). Set the box to output Dolby Digital and then the AVR will decode and output the appropriate signal. In my primary system using an HK 7550HD, I set the AVR for Logic 7 7.1 so it will post-process automatically each stream accordingly...
A. 2.0 > 7.1
B. 5.1 > 7.1

Just my $0.02...