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  • Dolby Pro-Logic

    Have an old Harman Kardon Dolby Pro Logic receiver which I have been using in stereo for some time. This is pre HDMI or optical inputs. It has 5 or 6 channels but as I understand it the surround and center information at the time was "encoded" in the stereo signal of the coaxial inputs. Is this still true for today? Meaning if there devices which extract hdmi audio into stereo is there anything in there that would steer some sound to the additional channels?

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  • #2
    They make hdmi to coaxial and optical to coaxial convertors. You just need to make sure the source sends a audio stream the your HK can decode

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    • #3
      The only major difference between the analog inputs you have and optical or HDMI is that the latter are digital. The content is the same. and Pro-Logic works with all of them.
      www.billfitzmaurice.com
      www.billfitzmaurice.info/forum

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      • #4
        Originally posted by devnull View Post
        They make hdmi to coaxial and optical to coaxial convertors. You just need to make sure the source sends a audio stream the your HK can decode
        Right so, my HK does not have optical or coaxial digital inputs. I'm pretty sure pro-logic was encoded within the stereo analog signal back in the days of VHS / laserdisc. I am wondering if the analog stereo signal today in modern sources like blue-ray or video game consoles still has surround information embedded in it.
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        • #5
          Originally posted by infamous_panda View Post

          Right so, my HK does not have optical or coaxial digital inputs. I'm pretty sure pro-logic was encoded within the stereo analog signal back in the days of VHS / laserdisc. I am wondering if the analog stereo signal today in modern sources like blue-ray or video game consoles still has surround information embedded in it.
          Sorry thought you had coaxial inputs. I know you can do software conversions of 5.1 down to pro logic using ffmpeg, don't know about hardware conversions. I'd probably try a couple of conversions using ffmpeg and see what happens. As an alternative, if using a pc as your source use ac3filter as the audio decoder and set the output to pro-logic.

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          • #6
            Originally posted by infamous_panda View Post
            I am wondering if the analog stereo signal today in modern sources like blue-ray or video game consoles still has surround information embedded in it.
            They do, but you'll also find that most modern sources do not have analog outputs, and TVs don't have analog inputs or outputs. I haven't used an RCA cable for years. Receivers still have RCA inputs, for use with legacy devices.

            www.billfitzmaurice.com
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            • #7
              A DAC digital to analog converter will take an optical signal and give you L/R RCA, check the features if you need to buy one.

              This article might help you.

              https://www.soundonsound.com/techniq...plained-part-2

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              • #8
                I think you have two different things going on.

                One is a digital to analog conversion. That takes a $10-20 adapter to convert PCM into stereo analog signal.

                The other is processing of that stereo signal into surround with ProLogic. That's as simple as:
                - common L/R content is CC signal, (L+R)
                - L/R remain
                - Surround is difference signal, (L-R) on one side and (R-L) on the other.

                Your HK is fine. You just need an HDMI to analog stereo or optical/coax audio to analog stereo adapter.

                Stay well,
                Frank

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                • infamous_panda
                  infamous_panda commented
                  Editing a comment
                  Actually just found that my projector which has hdmi in has a stereo analog out. I did a quick and dirty wire up to see if anything would be sent to the rear using my roku and youtube surround tests. results were disappointing but probably as good as what was going on in the 90s. Setting the roku to anything other than stereo output over the hdmi would cause a problems. I think i'll bite the bullet and get a receiver that is not 20 years old.

              • #9
                Originally posted by djg View Post
                A DAC digital to analog converter will take an optical signal and give you L/R RCA, check the features if you need to buy one.

                This article might help you.

                https://www.soundonsound.com/techniq...plained-part-2
                Thank you this was an interesting read.
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