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Converting DD5.1 to Pro Logic Matrixed Stereo?

F

FiddleFaddle

New Member
New member here!
Sorry if this is the wrong space to ask this.

I've got a very old JVC RX-903V receiver as part of a matched-component system that I love dearly. It was pretty high end for its day, but its day was 30 years ago. That said, it's been reliable for decades and has sentimental value as well, and I'm too attached to it to trade it for something else.

It's currently configured as part of a 5.0 (well, technically 4.0, since it's first-generation Pro Logic, so the rears are mono) home theater setup. All video sources are routed through the TV, which is connected via analog stereo line out to the receiver. The receiver ONLY has analog stereo inputs.

Its use is about 50% music, 25% TV/movies, and 25% games. I have it set up to play music sources in stereo and the TV audio in Pro Logic surround.

However, I've noticed that some newer sources (games, Blu-Ray, and streaming apps, in particular) that contain Dolby Digital or DTS audio do *not* have stereo audio that is matrixed for Dolby Surround/Pro Logic.

The TV offers analog stereo out, optical out, and ARC via HDMI. I've seen DACs that convert digital 5.1 audio to either analog stereo or analog 5.1, but I have not been able to find any that can encode the rear channels for Pro Logic on the fly and mix them into the stereo signal. The closest I've come is a transcoding ripping option in HandBrake, but that's not realtime and won't help with streaming sources and video games.

Does such a device exist? If not, is there any software that can be used to achieve this result (e.g., something that could be done through a Raspberry Pi)? I know my ancient JVC and its first-generation Pro Logic is a far cry from modern surround systems, but I'd love to be able to take proper advantage of the surround sound when sources contain surround data but don't include a version of it in the stereo mix.
 
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What sources do you use? If you have a Blu-ray player, does it have analog outs? Does your receiver have a multichannel analog input?
 
The receiver only has analog stereo inputs—no multichannel analog, no digital of any kind. It is a very early first-generation Pro Logic device; its cutting-edge new features were S-Video and a center channel output. It does just fine with anything that is matrixed for Dolby Surround/PL/PLII, but several Blu-Rays and streaming services don't really seem to include that in the stereo mix any more, and a lot of game consoles have native 5.1 sound but don't do PLII encoding.

My sources are a wide variety of game consoles (including a PS3 for Blu-Ray playback) and the TV itself, which is an Android-based Sony XBR-55X850C. (We run native apps on the TV for streaming services.) The TV can output via analog stereo, optical, or ARC. However, as far as I can tell, it doesn't do any sort of PL/PLII encoding when it downmixes to stereo.

That's why I'm very specifically looking for some sort of Pro Logic encoder. It's the only way to get multichannel audio into the receiver.
 
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AFAIK there is no such thing as a Dolby Pro Logic encoder for home use. A Dolby pro logic signal is a two-channel signal to which some phase changes (matrixed) are applied to the signal. There are no separate surround channels in mono or stereo.

If you've been around long enough to have experienced matrixed stereo recordings, you should be familiar with SQ, and QS. They were matrixed schemes invented during the Quad hype years. Dolby Pro Logic works in pretty much the same way. In fact, it does a pretty good job on QS and SQ recordings.

FWIW: Just about any stereo signal will produce some "surround" sound when run through a Dolby Pro Logic decoder or a QS or SQ decoder.
 
I don't know if anyone is interested, but I managed to solve this issue last year, in a slightly roundabout way:

1. All video sources are connected directly to the TV via HDMI.

2. The TV outputs Dolby Digital audio via optical connection to an old Harmon Kardon ADP-303 decoder (with the subwoofer channel set to "off").

3. The individual analog channels from the ADP-303 are fed into a Dolby Laboratories SEU4 surround encoder unit, which converts 4-channel analog surround (L,C,R,S—I combined the two rear outputs from the ADP-303 using a stereo RCA combiner) into matrixed 2-channel audio in real time.

4. The matrixed 2-channel output from the SEU4 is fed to the RX-903v, which is able to decode the surround sound correctly.

This way, the Pro Logic-only receiver is only to decode the rear channels from modern source material much more accurately than whatever it would happen to stick on the rears from the TV's downmixed stereo. In the future, I'd be interested in finding a higher-quality DAC than the ADP-303 (though, on the positive side, the ADP-303 does have an offer RF AC3 decoding to get 5.1 sound from LaserDiscs). Also, it's a shame that there doesn't seem to be a single device that can take the place of both the ADP-303 and the SEU4 (which is what I was looking for in my original post), though I admit this is a pretty extreme edge case in terms of usage. But at this point, part of the fun is seeing how far I can go with this old beast.
 
Let me get this straight. You’re taking ProLogic, decoding it to surround analog (4ch), then blending that back to stereo to play through a ProLogic receiver on a pair of stereo speakers?

I’d move on, use the stereo somewhere else for music and get modern gear for movies.

The performance available for relatively low cost is worlds beyond letting ProLogic contaminate your experience, lol.
 
No.

I'm:
1. taking Dolby Digital (which my receiver doesn't support)
2. decoding it to 4-channel analog surround (which my receiver also doesn't support; it has Pro Logic decoding, but not a discrete multichannel input)
3. then encoding that into a Pro Logic matrixed signal (which my receiver does support)
for playback through my receiver, which is connected to a 5.0 speaker setup (2x Polk S60's in front, 2x Polk S20's in rear, and a Polk S30 for the center).

This is my receiver: https://hifi-wiki.com/index.php/JVC_RX-903
 
FiddleFaddle said:
No.

I'm:
1. taking Dolby Digital (which my receiver doesn't support)
2. decoding it to 4-channel analog surround (which my receiver also doesn't support; it has Pro Logic decoding, but not a discrete multichannel input)
3. then encoding that into a Pro Logic matrixed signal (which my receiver does support)
for playback through my receiver, which is connected to a 5.0 speaker setup (2x Polk S60's in front, 2x Polk S20's in rear, and a Polk S30 for the center).

This is my receiver: https://hifi-wiki.com/index.php/JVC_RX-903
Click to expand...
You can't do what you want. No ProLogic encoders you can buy. Why can't you just buy a Dolby Digital capable receiver? (they're available used for reasonable money, even nicer ones).
 
KentTeffeteller said:
You can't do what you want. No ProLogic encoders you can buy. Why can't you just buy a Dolby Digital capable receiver? (they're available used for reasonable money, even nicer ones).
Click to expand...
Because he enjoys the receiver he has,not everyone needs or wants new.
 
KentTeffeteller said:
You can't do what you want. No ProLogic encoders you can buy. Why can't you just buy a Dolby Digital capable receiver? (they're available used for reasonable money, even nicer ones).
Click to expand...
Except I already am, as mentioned in my May 31 post. This problem is solved.

I'm using a Dolby SEU4 encoder, which is a piece of professional rack-mount equipment that converts discrete 4-channel analog sound into matrixed 2-channel surround suitable for Pro Logic decoding, with no noticeable delay. IIRC it only cost about $30, as there's not a lot of use for them any more. It'd be nice to have a single box that handles both the DD decoding and the Pro Logic encoding rather than having to use two separate components, but I'm pretty sure that doesn't exist in a form that would suit my purpose.

As to the why: I like the receiver I have.
  • I like its sound signature. Just perfectly clean, detailed, neutral sound that you can tweak to your liking with the source-specific 7-band equalizer. Sure its surround processor is hopelessly dated, but it only spends about half its time on surround-sound content anyway.
  • I like its looks.
  • I like the way it operates. It's charmingly dated in some ways, but remarkably forward-thinking in others. And the way the features are programmed is straightforward in a way that I like while still offering quite a bit of granular control.
  • I like the fact that it's built like a tank. This receiver is 35 years old—it was one of the earliest models of what we'd think of as a modern home theater receiver—and it's never given me an ounce of trouble.
  • I have sentimental attachment to it. I bought it secondhand for a pittance when I was in college (it was old even then, but it had a great, clean sound and it had the same design language as the JVC CD player I grew up with), and it's been with me through every move and every life milestone for the past quarter-century.
  • I like the fact that it has FIVE analog I/O loops: Tape 1, Tape 2, VCR 1, VCR 2, and DAT. (And yes, I use them all. Tape 1 is connected to a good-quality dual-well deck for longer playback during social gatherings, though I don't typically use it for recording. Tape 2 is connected to a matrixed stack of 3-head cassette decks that I use for producing small-run batches of tapes. VCR 1 is my VCR. VCR 2 is my LaserDisc player on the input side, and the outputs route to a spectrum analyzer for display. DAT is connected to a bidirectional stereo DAC that I can use to play back from or record to my computer, phone, or other digital device.)
  • I like the fact that it's a matched component to several other components in my system. It gives my setup a nice visual consistency, plus I can use the JVC CompuLink control system.
  • I like the "game" of it. Part of the fun is seeing how far I can push older or more limited gear to meet modern use cases.
  • I don't like creating waste. Why replace something that's been doing its job just fine for the last quarter-century?
 
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