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6-channel analog audio to HDMI audio box?

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  • #16
    A PC based solution will always have a considerable lag. And you won't be able to fix that for film, I guess, unless you limit the application to certain setups which allow a re-arrangement of the sound reader.

    I also thought about a Raspberry PI, you would need some audio AD board/USB interface, and some basic sofware (the PIs HDMI output is multichannel LPCM capable).
    But - again, making your own 3*2 AD-AES3 converter from off-the-shelf parts is far more easy I think.

    Wondering wether some AVRs will feed discrete multichannel analog inputs into their HDMI outputs? Those that I know personally will only route analog multichannel audio to the pre-amp and amplifier outputs - but I guess some would also digitize and feed it into it's main HDMI out.

    An AVR would also solve some of the CP950's consumer format decoding inabilities.
    Last edited by Carsten Kurz; 04-05-2021, 06:24 AM.


    • #17
      Consumer decoding is not an issue (they're not using the HDMI input or playing any alternative content in that screen): all we'd need it for is film sound (analog SVA and SR-D). Should they ever wish to do a 35mm show, I'd likely experiment with the PC option first, reducing the global delay to zero in both the 500 and the 950 if needed. As mentioned earlier, this is not a project they're prepared to spend serious money on, which pushes us down the cheap 'n dirty route.


      • #18
        The real cheap and dirty route, but completely viable, is an analog A/B switch and just have duplicate B-chains. If your crossovers are in the CP950 then those would need to be duplicated on the film side too...there may be cards floating around for the CP500 to do biamp crossovers internally otherwise do those externally too.


        • #19
          The real cheap and dirty route: $ 580.

          AB-8 8-Channel Mic / Line Switcher

          AB-8 8-Channel Mic / Line Switcher - Catalog - Whirlwind (


          The AB-8 is an 8-channel, balanced, bi-directional signal switcher, 1 in - 2 out or 2 in - 1 out per channel.

          • Eight channels of balanced A - B switching for line, mic or MIDI signals.
          • Each of the eight channels can be individually switched or assigned to a Master Control circuit.
          • Master switching is controlled through front panel pushbuttons, optional footswitch or automatically triggered by loss of signal on channel one of A input.
          • Can be configured as two inputs to one output, one input to two outputs or a mixture of both.
          • Multiple units can be ganged together under Master Control of the first unit or through control Voltage input.
          • Indicator lights show status of each channel.
          • AUTO SWITCH functions automatically switches to redundant copy of backing tracks for live performance.
          • AUTO SWITCH has sensitivity and hold time controls to accommodate input signal levels from -20dB to +20dB
          • Easily switch from tracking to mixing in recording setups.
          • All signal paths revert A to Common when AC power is removed.
          • Internal DIP switches configure ground path switching and DC Voltage blocking requirements.


          • #20
            Joao - see Sean's suggestion for this, and my response above. The gotcha is the tri-amped stage channels, meaning that I'd need two of these units.

            Bottom line - this is do-able, but there is no magic bullet (the magic bullet would have been a six-channel analog to audio only LPCM HDMI box, but apart from the seriously pricey Arvus, no such thing exists). There is either going to be a significant cost in technology, in rewiring/reconfiguring labor, or both. The customer is not too fussed. After they converted to digital, they kept the 35mm projector and platter, plus the CP500, in the biggest house in the plex, just in case they'd ever need it for a special show. That was almost a decade ago, and so far they haven't. They've played a reel of trailers every now and again to keep the projector and platter ticking over, but haven't been called upon to play a 35mm show to the paying public.

            My gut feeling is that we'll do nothing for the time being, but that there is a small chance that they'll be asked to do a 35mm show of a Tarantino or Nolan type movie at some point, in which case I'll be asked to come up with a solution with an insane deadline attached, and bugger the budget. If so, I have this thread bookmarked, and thanks for everyone's suggestions.


            • #21
              Easiest way: Replace old Dolby 750 for another working Dolby 750 OR Datasat APXX, if you dont need Dolby Atmos.

              At this moment there's no easy way to convert analog multichannel to AES/EBU - S/PDIF or TOSLINK and then embedde stream to HDMI. It's a crazy process to get analog in Dolby 950! Half solution: $69.00 Premium HDMI Audio Embedder + Analog/Digital Audio To HDMI Converter (converting analog stereo or multi-channel digital sound to HDMI output for audio alone while no video content is required).