Decoding quad vinyl with ProLogic IIx, Neural THX, etc. - AVS Forum
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post #1 of 6 Old 02-07-2012, 10:42 AM - Thread Starter
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A technically obsolete, yet valid source of surround-sound music is quadraphonic vinyl! Of course, there were several competing standards for 4-channel music in the '70s, which ultimately led to its lack of uptake by consumers.

But for those of us who crave high-quality multi-channel music, I think it makes sense to have a quad-capable vinyl rig and keep on the lookout for multichannel vinyl releases, in addition to all the digital formats.

I've had reasonbly good success decoding Sansui QS format quad vinyl using a Dolby ProLogic IIx decoder. It appears to map to 7.1 pretty well and give an immersive effect.

It's my understanding that the CBS SQ format used a different matrixing method that isn't compatible with the Dolby ProLogic series of decoders. Has anyone tried SQ with other matrix surround decoders, such as Neural THX 7.1?

And then CD-4 would require a phono preamp and outboard decoder, with 4 discrete analog channels as input. The vinyl-to-CD-4 decoder chain would need to be all analog to preserve the ultrasonic carrier and back channels.

Anyone else doing this?

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post #2 of 6 Old 02-08-2012, 02:44 AM
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I thought i'd add my views here.

Dolby PL can only give an artificial surround effect with QS. It's not comaptible with it at all, so an accurate image is, i'm sorry to say, impossible.

As some may know, Dolby PL was based on SQ, but altered to be incompatible, and nothing decodes SQ well apart from a dedicated decoder, although i'm sure that any manufacturer that modifies the Nueral decoder to work accuratley to decoded SQ would find themselves with high sales figures.

After creating the accurate software decoding solutions, i had hoped that some bright spark would start work on a realtime software solution for those wishing to decode the matrix encoded material from the 70's

But, the problems of creating accurate logic curcuitry in software is still probably beyond what is possible.

As to CD-4, the only way to decode those albums is to use a CD4 Demodulator
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post #3 of 6 Old 02-08-2012, 08:20 AM - Thread Starter
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Actually, I had better than an "artificial" surround effect with the QS / ProLogic IIx combo.

I tried a QS test LP that had tracks encoded to test steering / image placement. The results were actually correct, with effects placed in the proper directions. This despite the decoder not being identical and the speaker layout being different than the traditional quad 4.0 setup.

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post #4 of 6 Old 09-22-2012, 06:22 PM
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Well I have just been schooled. I was only aware of the 4 channel discrete type of Quadraphonics. I'm just getting back into vinyl, and becoming an incredibly incorrigible audiophile more, and more. It started with th AR-15 speakers my uncle gave me and, probably more due to all the SACD's and DVD-Audio's I was into, being a hopeless surround junkie. The sound quality of those formats finally opened my ears up, and I've become rather insatiable.
Back to the question about THX Neural decoding; I am in the market for a new receiver, and have come to take the amazing things it does with a common 2-channel source, let alone anything with encoding...even Dolby encoding, if you try the PLIIx, and then the THX, more often then not the THX leaves you stunned. So in response to the original question, I have unshakable faith that the THX would undoubtedly reproduce the original encoded channels true to their original specs, and then follow through and "fill" the remaining 3.1 channels. I would be surprised if it didn't make it BETTER than the original. Also, for a purist, on the amp I have now, it would be possible to just have the four channels, or 4.1 for a bit more bass.
Hoping that I can find more help on Quadraphonics. Especially before I make my decision on a new amp and/or receiver, and a turntable. I'm assuming that the CD-4 needs a specific turntable, being that there are four discrete channels. Also I would love to get my AR's up and running, but, even if I use a bi-amp method, I cannot find any surround set-up with the massive power handling that they need. It was extremely expensive just to run them in stereo. New to this, but looking forward to meeting a lot of really neat people with the same audio affliction as me:)
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post #5 of 6 Old 09-22-2012, 06:24 PM
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Well I have just been schooled. I was only aware of the 4 channel discrete type of Quadraphonics. I'm just getting back into vinyl, and becoming an incredibly incorrigible audiophile more, and more. It started with th AR-15 speakers my uncle gave me and, probably more due to all the SACD's and DVD-Audio's I was into, being a hopeless surround junkie. The sound quality of those formats finally opened my ears up, and I've become rather insatiable.
Back to the question about THX Neural decoding; I am in the market for a new receiver, and have come to take the amazing things it does with a common 2-channel source, let alone anything with encoding...even Dolby encoding, if you try the PLIIx, and then the THX, more often then not the THX leaves you stunned. So in response to the original question, I have unshakable faith that the THX would undoubtedly reproduce the original encoded channels true to their original specs, and then follow through and "fill" the remaining 3.1 channels. I would be surprised if it didn't make it BETTER than the original. Also, for a purist, on the amp I have now, it would be possible to just have the four channels, or 4.1 for a bit more bass.
Hoping that I can find more help on Quadraphonics. Especially before I make my decision on a new amp and/or receiver, and a turntable. I'm assuming that the CD-4 needs a specific turntable, being that there are four discrete channels. Also I would love to get my AR's up and running, but, even if I use a bi-amp method, I cannot find any surround set-up with the massive power handling that they need. It was extremely expensive just to run them in stereo. New to this, but looking forward to meeting a lot of really neat people with the same audio affliction as me:)
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post #6 of 6 Old 09-23-2012, 08:49 PM
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Colin,

How did you feed the quad to the DPLIIx decoder ?

My own experience with quad on Blu-ray, from the DSOTM Immersion set, has shown that DPLIIx will turn 4.0 into 6.0, but it doesn't extract a center channel.

Cheers,
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