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Changing to Dolby Digital or DTs-x when the signal is Stereo only


Novice Member
I am using the Denon AVr 4500.

Currently using ARC to hook up TV to amp, so when watching live TV, this is how the amp is getting the signal (don't have sky box of virgin at this time).

Usually when I turn the amp on, it will default to stereo, and play just through the two front's.

However, I can change the settings on the amp to various options, i.e. DD or DTS -neutral and more.
Interestingly, when I look at this setting on the phone app, it shows all speakers working (in green) but not the subwoofer.

My question is, what kind of sound am I actually getting from the amp / what is it doing. If the ARC from TV signal is only getting stereo.


Distinguished Member
Dolby Digital and DTS:X are formats and not modes. You can get 2 channel audio sources that are encoded as Dolby Digital, but DTS:X is an object orientated audio format who's metadata is conveyed in association with 7.1 DTS-HD Master Audio.

ARC has no ability to convey DTS:X metadata or HD audio formats such as DTS-HD Master Audio or Dolby TrueHD. You can convey Atmos metadata along with Dolby Digital Plus using ARC though, but not all TVs facilitate it. The content itself will need to have been encoded with it in order for you to be able to access it. Freeview do not convey anything encoded with DTS, DTS:X, Atmos or one of the HD formats.

If getting stereo from your TV's Freeview tuner then you are either getting 2 channel Dolby Digital or 2 Channel PCM. The receiver will indicate which format it is receiving on its front panel display. Many HD channels use Dolby Digital 2 channel and 5.1 while all SD variants use 2 channel PCM. You'd also have to configure your TV's digital audio output configuration appropriately if wanting to access anything but 2 channel PCM from the TV. Most TVs have a default PCM setting that ordinarilly downlixes all output to 2 channel PCM.

If all speakers are engaged in association with a 2 channel source then you are applying upmixing to it. THis is processing that creates pseudo channels of audio for the speakers present that the incoming audio lacks discrete channels for. Modes such as Dolby Surround or Neural"X would be the most commonly used modes for this purpose on your receiver.

You need to differentiate between audio formats and processing modes.

Deleted member 39241

Applying upmixing to a movie or tv soundtrack that has a stereo audio mix is common practice, I do this all the time and get great results.

With Dolby Surround you have the option to add 'centre spread' which retains the original stereo mix of the dialogue, but adds it to the centre channel as well. Without this switched on, the dialogue is mixed down to mono and sent entirely to the centre speaker. I prefer centre spread on, but you can experiment yourself and see which you prefer.

The fact that the subwoofer is not lit indicates that there is no LFE channel in the original mix. That is it is a 2.0 audio source, rather than a 2.1. The subwoofer would still be working for taking the bass frequencies from any speakers that you have set to small rather than large in the speaker set-up settings.

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