If you could purchase any CD-4 demodulator.....

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Doug G.

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I think that yeah, a lot of people on this board wouldn't consider buying one for a reasonable price. But talk about limited appeal! :cautious: Maybe it could be built into something that's already semi-popular. I highly doubt anyone would manufacture something like this only because they wouldn't make a lot of money.
Alas, if only more people could hear how wonderful CD-4 is when working properly...

Doug
 

Doug G.

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And who knows, maybe some genius like Lou Dorren would have figured out how to carry CD-4 on CD's! Of course, I realize it wouldn't have been necessary.

Doug
 

par4ken

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And who knows, maybe some genius like Lou Dorren would have figured out how to carry CD-4 on CD's! Of course, I realize it wouldn't have been necessary.

Doug
Somewhere there was a post where the author had recorded CD-4 record(s) by tapping into his demodulator, He then burned a DVD-Audio disc that could be played back through the demodulator! I thought that it was rather cool! Not really necessary but still very cool. I wish that I could find that post again, I don't remember if it was posted here at QQ or somewhere else.
 

kfbkfb

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Interesting statement in the AES paper about the Pspatial Audio CD-4 decoder:

Notwithstanding some of
the signal processing stages noted above in which we have
taken advantage of non-real-time nature of the application,
and where a different engineering approach would be re-
quired, there are few reasons why the majority of the new
decoder algorithm could not form the basis of a real-time
DSP decoder.


Anyone want to build/sell a real time DSP based CD-4 hardware decoder?


Kirk Bayne
 

furui_suterioo

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Somewhere there was a post where the author had recorded CD-4 record(s) by tapping into his demodulator, He then burned a DVD-Audio disc that could be played back through the demodulator! I thought that it was rather cool! Not really necessary but still very cool. I wish that I could find that post again, I don't remember if it was posted here at QQ or somewhere else.
I've been wanting to try this but too afraid I might damage the phono input on the demodulator. I wonder of it's any less risky to connect a line level at low volume to the ceramic input on the demodulator. It would be neat to have a file of raw CD-4 test tones. But not very useful as you've said.
 

par4ken

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I've been wanting to try this but too afraid I might damage the phono input on the demodulator. I wonder of it's any less risky to connect a line level at low volume to the ceramic input on the demodulator. It would be neat to have a file of raw CD-4 test tones. But not very useful as you've said.
As I recall he tapped the output from the Demodulators pre-amp before being filtered, then fed it back into the same spot. So a slight mod would be needed to the demodulator. I wish I had the link, if it's still posted.
 

furui_suterioo

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Been thinking, would be interesting if one could digitally encode a discrete source into CD-4 and feed it into the demodulator to test ultimate performance. Doesn't seem like it would be difficult to replicate a carrier and sum/difference signals in audio software.
 

kfbkfb

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IIRC, the Louis Dorren CD-4 demod also had L and R line level inputs so that a digitally saved CD-4 disc (the whole frequency spectrum up to 45kHz wo/RIAA deemphasis) could be played into it and the demod would process the signal as if it was an actual CD-4 disc playing.


Kirk Bayne
 

MidiMagic

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Aren't we assuming that the record has not already been ruined?

I have never heard a CD-4 record play correctly through its entire length. There was always something that ruined the rendition.
 

barfle

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Even if they perfected it, I guess CD-4 would have died when vinyl died back when. But, I bet regular CDs would have been 4 channel as a standard. 🙂
I attended a seminar about 15 years ago on CD technology, and while the presenter didn’t go ant deeper into the topic, he said that the red book includes an option for four channels. Ahh, the mysteries of that littlek red book…
 

soesbeout

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If I could purchase any CD-4 Demodulator it would be Lou Doran's modern design. Many people here were ready to order as soon as it became available for purchase. Sadly Lou passed away before completing his project, I wonder if any working prototypes exist?
I wonder if there are schematics somewhere that could be found.
 

Owen Smith

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I attended a seminar about 15 years ago on CD technology, and while the presenter didn’t go ant deeper into the topic, he said that the red book includes an option for four channels. Ahh, the mysteries of that littlek red book…
It just halved the running time and had four 16/44.1 channels instead of two. Nothing complicated.
 

fredblue

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There were obviously shortcomings in the setups.

Doug
i agree - or maybe they have just been dreadfully unlucky. even with what i feel have been less than perfect setups, with varying combinations of cart and demodulator and discs in all sorts of condition, i have scores of CD-4 LPs that have resulted in pleasing 4-channel sound all the way through to the label, some even through both sides of the record! 😉 👍
 

Doug G.

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i agree - or maybe they have just been dreadfully unlucky. even with what i feel have been less than perfect setups, with varying combinations of cart and demodulator and discs in all sorts of condition, i have scores of CD-4 LPs that have resulted in pleasing 4-channel sound all the way through to the label, some even through both sides of the record! 😉 👍
Yes and my reply was based on my present day setup resulting in playback no different from regular two channel LP's

Doug
 
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