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Confusion about digital audio, got some questions...

Discussion in 'Receivers and amplifiers' started by Burnist, Jan 13, 2005.

  1. Burnist

    Burnist Member

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    Hi all,

    Forgive my ignorance but I'm new to the whole home theater thing. Got a Sony home theater system last week and its my first experience with that kind of thing. I know, I know, I was living in the stone age...

    So my question is this. Can digital audio be transferred by RCA cables? It is my understanding that either a Coax or an Optical cable must be used to transfer digital audio and that digital audio cannot be transferred via plain RCA cables. Is this correct?

    I ask this because here is my situation. My DVD player is hooked up by a monster coax cable. The receiver shows the digital audio is being decoded, everything sounds great. But what about broadcasts on TV that show presented in dolby digital? My cable box only has RCA outputs on it, so its hooked up to my home theater receiver using standard RCA cables. I notice that whenever a show comes on TV that says its presented in dolby digital, my receiver does not decode it. The same goes for my Gamecube too. I play Metroid Prime 2 and right at the start up screen it says Dolby Digital 2 or something like that. I have my Gamecube hooked up only by RCA cables so my receiver will not be able to decode the digital info right?

    I hope I'm not sounding retarded. Thanks for any clarification as I'm new to this all. I'd like to be able to decode and enjoy all digital audio signals if possible. Maybe I'm doing something wrong? Thanks in advance!
     
  2. bpitt

    bpitt Member

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    Your question is a valid one. The answer is no, Dolby Digital cannot be transfered through RCA cables. You need like you said digital coax or optical cables. You say your cable box only has RCA output? Do you mean it only has the Red and White RCA outputs? I ask this because digital coax looks just like an RCA output except its black or orange in color and is usually labeled as being a digital output. Also you say your DVD player is hooked up via monster coax cable? Do you mean the audio output of the DVD is hooked up via digital coax? If so this means your reciever has a digital coax input and you should call your cable company and see if they offer a cable box with digital audio output. As for your Gamecube it probably has some sort of digital audio output.


    I actually read that RCA cables can carry a digital coax output but only for a very small distance.

    I have done lots of research so write back if you have more questions.
     
  3. Burnist

    Burnist Member

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    Bpitt thank you so much for that info. You are the man for being so helpful. It all makes sense now.

    Yes my cable box only has the white and red RCA outputs so I'll do what you suggest and ask the cable company for one with digital output. And about my DVD player. Its an older one and only has the orange digital coax out which is what I'm using. My receiver has both the coax digital input and the optical as well with the optical just being unused right now.

    Well thanks again for your answers!
     
  4. bpitt

    bpitt Member

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    Anytime dude. Good luck with the cable company. I've had a tough time in the past getting someone who knows what they're talking about. I had a look at my cable boxes and my high definition box has the digital output but my other regular cable box does not. I don't know if they offer regular cable boxes with the digital output but its worth the try.
     
  5. Nixxter

    Nixxter Member

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    When checking out new cable boxes, keep in mind that sometimes the coaxial digital output is labelled as "AC3" (not often). It's the same thing but I guess an older name. My old digital cable box is labelled like that and I have it hooked up to my surround sound's coaxial input with great results. If you are able to choose between optical or coaxial on your new cable box, I would go with optical. One of my DVD players has both outputs and I swear the optical sounds way better. The only drawback is that optical cables are more brittle than coaxial and must be handled carefully and once hooked up, should have no kinks to allow proper light flow. Hope this helps. Good luck in your search!
     
  6. CDSurf

    CDSurf Member

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    bpitt,

    Then why do a lot of plasma TV's have a digital audio OUT, but only RCA audio IN jacks? Is some sort of conversion-to-digital performed on the audio signal once it comes in via the RCA jacks?

    Thanks!
    CD
     
  7. wolfniggr

    wolfniggr Regular member

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    Ok, time for some minor corrections. You don't need optic or coax cables to listen to digital sound. If you want to listen to true Dolby digital or Dts signals then yes, you do need a digital cable. I prefer optic cables bcause they are not prone to interference. As for your GameCube, if your receiver supports Dolby Pro Logic 2, then it will convert your analog signal to 5.1 or 6.1 or 7.1 depending on your receiver. Though digital cables give you true digital suround sound, in order to listen to DVD audio disc or SACD sound, you need a seperate analog connection for each channel because the digital cables can't handle the amount of data that is transfered to your receiver. You may still listen to audio DVDs with a digital connection, but it will be a different track with lower bit rate. The same for DTS audio discs. There is a lot of great info and history on Dolby digital and DTS on their own websites. They go into great detail as to how they work. As for the plasma question, HD monitors with built in digital recievers will come with the digital output so you could connect it to your receiver. There is no reason to have a digital input on your tv if it only has 2 speakers or non at all. That's what a receiver is for.
     
  8. bpitt

    bpitt Member

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    Ok, now i'm a bit confused. Wolfniggr, You say HD monitors with built in digital receivers have digital output for connecting to your receiver right? My question is this. A built in digital receiver will recieve it signal from where?, standard coax(like cable companies use), broadcast signals, or other analog sources such as rca? Maybe I'm not understanding.
     
  9. wolfniggr

    wolfniggr Regular member

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    bpitt, the sources you mentioned except for the rca inputs will output a signal from the optic output so long as there's digital signal comming from those cables. A HDMI connection will produce a signal through the optic output as well.

    Keep in mind that the signal that comes through an optic or digital coax cable isn't always 5.1. A digital dolby signal can be 1.0, 2.0, 2.1, 3.0, 3.1 and so on up to 5.1. If you have a receiver with prologic 2 then it will seperate the signal to output sound to all your speakers if the soundtrack doesn't provide a discrete signal to each speaker.

    Then you have Dolby Digital EX which has an extra signal imbedded within it. This can give you 6.1 surround sound(If your receiver can decode dolby EX)or 7.1 with prologic helping. DTS ES (my favorite) also gives you more than 5.1 sorround and unlike dolby EX, it has discrete signals going to every speaker. Hope I didn't confuse the shit out of you even more and if you have more questions, please ask. Like I wrote before, if you go to the dolby and dts websites there a ton of articles on how they work and how it all began. Very interesting stuff.
     
    Last edited: Feb 10, 2005
  10. bpitt

    bpitt Member

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    Thanks for the response Wolf. Ok so if a dolby digital signal reaches my home through standard coax cable (from the cable company) does that mean that standard coax is a digital cable? I don't thinks so. Or is the dolby digital converted to analog, sent through the cable and once it reaches my cable box converted back to a digital? If this is the case then what if my cable box is hooked to to my tv with standard coax again. Does that mean that we go through another conversion again and that my tv must be able to convert the signal back to digital? In this case I understand why one would want to use either digital coax or optical cables to get the sound to my receiver. And finally my last question, If this is the case why would on one want to avoid the conversion by hooking up the sound with digital optical or coax cable if it will still be converted before when it goes through the standard coax.

    Now I hope I havn't confused you I'm just trying to get this down.

    By the way thanks for the dolby website. I did check it out yesterday. Somewhat helpful.

    Look forward to your response.
     
  11. wolfniggr

    wolfniggr Regular member

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    First, digital cable doesn't mean all channels are digital. Usually only certain networks, ppv and movie channels broadcast in digital or HD. In order to view these cable channels you need a digital cable box. If you connect the box to your tv via a coax cable(not recomeneded) [bold]some[/bold] built in decoders will output a decent optic signal. Doing it this way is not a good idea anyway, and will cause you to loose the true audio signal. Some displays output a converted digital signal from an analog source(regular tv broadcast or rca), but the signal is recognized as a stereo or dolby sourround(matrix) signal by your receiver and pro logic will kick in. The best thing to do for great picture and sound is to send only a video signal to your tv(component,dvi,RGB) and the audio directly to your receiver. Even though certain displays have an optic output, it doesn't mean you have to use it.
     
  12. bpitt

    bpitt Member

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    Wolf, I think you misunderstood my question. I understand what you are saying but my confusion was in how the dolby digital signal gets to your house. The cable guy will hook up a standard coax cable from the pole to your house. From what I understand this is not a digital cable. So how is the digital signal reaching my house through a analog cable? Conversions? I know it does come in digital otherwise the cable companies would not advertise this feature. If you or anyone else knows please post a response. Thanks.
     
  13. wolfniggr

    wolfniggr Regular member

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    Digital signals can be transfered through the coax cable(it's not standard, I forget the guage size) that comes from the pole. In order to decode this data you need a digital cable box(This is key). You can also go on the internet using this cable. I believe the cable company has control of the exact signal that goes to your house. Can't tell you exactly how it works only that it does.
     
  14. bpitt

    bpitt Member

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    Thanks for the help Wolf.
     
  15. byngo

    byngo Regular member

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    Just to come back to reality a little here and summarise.
    Take stock of how many programs you can watch that are actually broadcast in dolby digital 5.1 or DTS???
    The result equates to you watching 98% of DVD's in True digital sound of usually 5.1 and sometimes DTS and 98% of all broadcasts in either stereo or a clever matrix of stereo called dolby pro-logic 2.
    Stereo and DPL 2 is fine through decent RCA.
    Digital is only true through optical or Digital co-axial cable and coming from a digital source.
     

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