Lou Dorren: A new CD-4 Demodulator!!! [ARCHIVE]

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Perish the thought! First of all, cases don't cost that much. Second, any retrofit for a case not made for it would not be as good, unless you made the board exactly the same size and shape of the board it replaces. Third, there are only so many demodulators in the world, though they are not as rare as ,say, an Audionics Space and Image Composer, It would be a disservice to future quaddies (who might not even be born yet) to destroy perfectly useable or repairable demodulators such as the 4DD5, which is a very good demodulator in it's own right. You yourself should retain one of these demods in case the Lou Dorren unit fails, for as the years go by, some parts will not be availlable, and you may need a fallback. The older demods have mostly discrete components, and hopefully parts will be availlable for years to come. Broken demods should be retained if for nothing else, to provide parts for fixable demods. Such would be the case for a demod with a cracked board, or a burned up power transformer, or a bad mode switch. As we all pass from this life, we will release quad recordings that people will want to hear. They will need something to demodulate them. Unwanted true quad gear, even broken gear, should be sold on Ebay, rather than being discarded, so that others may enjoy quad. This is especially true with decoders and demodulators and tape recorders. A quick check on Ebay reveals that CD-4 demodulators are getting more expensive, indicating increasing rareness. As time goes on, we will not be the only generation to enjoy this "failed experiment".
 
apologies in advance for the ignorant question but can someone talk me through this...I'm assuming I can put the grado with the kit on any tt I want, run that tt into the modulator, which will then attach only to a quad receiver? is this correct?
 
Hi epi-centre,
Would attach to a home-theater amp via the line in - you would use the 5 channel inputs that would normally be use for a DVD I would expect.

Yes, or you could just use two stereo integrated amplifiers or receivers (or one of each). You would have two volume controls (front and rear), but that would actually be a good thing (better balancing flexibility).
 
could I use the preamp with 2 channel if I just needed to use it w/ a strain guage cartrige?
 
could I use the preamp with 2 channel if I just needed to use it w/ a strain guage cartrige?

I have no idea why you would do that. Perhaps you could explain. Is it because you want to input the demodulator from your stereo preamp? If so, then the answer is no. The demodulator will have to be connected to your turntable. Why don't you give us more information, starting with what components you have. This is all too abstract to give you any solid advice.

On another note, with the Canadian dollar worth about US$1.05 ... this is an excellent time to buy a new demodulator!
 
I have no idea why you would do that. Perhaps you could explain. Is it because you want to input the demodulator from your stereo preamp? If so, then the answer is no. The demodulator will have to be connected to your turntable. Why don't you give us more information, starting with what components you have. This is all too abstract to give you any solid advice.

On another note, with the Canadian dollar worth about US$1.05 ... this is an excellent time to buy a new demodulator!

hey QZ, I just have an older sansui amp and currently have 2 tt's..one is an older panasonic quad with the panny quad cart but that I run, the panny tt has a built in demodulator that is not exactly elite (and the tt is no great shakes either), I run either pair of the rca's into my aux on my old sansui amp and the strain guage cart sounds really great in 2 channel.

What I want to do (before I get quad going) is to move the panny cart to a nicer tt and then use this demodulator to just run in 2 channel. I think that should work.
 
I guess I thought you were clear enough and yes, you can just run in two channel mode, since the new demodulator supports SG cartridges, plus have the option of going four channel in the future which, of course, almost all of us on this forum would recommend you doing.

\:^)

EDIT: OK, if I would have just read your entire post carefully, I would have seen your (before I get quad going). Doh!

Doug
 
no worries guys, I'm interested in Quad for sure but want to find a nice receiver first, I don't want to keep buying and upgrading over and over.
 
Hi Folks,

I have a Grado gold1, and have been studying its performance....

Specifically it appears to have (confirmed by both my own and third party measurements) a resonance focused around 12kHz - this would under normal circumstances imply phase issues beginning at perhaps 10kHz - and potentially extending out past the resonant peak.

This would normally cause issues with CD4 decoding.

Depends of course on the type and frequency response profile of the associated phase non-linearity. - as I have no way of measuring phase non linearity, all I can say is I know there is a phase non-linearity as all resonant peaks involve phase N-L but some types have phase N-L beginning with the resonance and getting worse from there onwards, others have a phase N-L that begins and ends with the resonance.

If the latter behaviour is how the Gold behaves this is probably a non issue (as by the time the 15kHz cutoff is reached we are past the resonance - so no impact on the carrier frequencies).

With the fitting of the Shibata stylus, we are looking at a change to the cantilever... differing mass, differing bonding, the process may add or detract from the damping material applied along the length of the gold cantilever.

So my question is:
What is the expected resonant behaviour of the new CD4 version of the Grado Gold1?


By the way has the new cartridge been named yet?
It's resonant behaviour is likely to be different to a Gold1, which will change its "tone" - the shibata will also change HF response - so really it deserves its own name.... Grado CD4? (bit boring really...)

bye for now

David
 
I have used dual amplifiers for a long time. When DTS came out with 5.1 surround, I just added a third amplifier, all identical. It works out great. I use Sansui AU717's. A vintage amp from the quad era that is stereo. It is also from the high quality era in hifi, which ran concurrently with the quad era. Not to knock modern stuff, but most of those companies that were prevalent back then went away because they cut their quality and tried to live off of their name.

The Quadfather
 
Hello Everyone,

First, Happy Holidays to everyone and may the New Year have good things for all. As a gift to all the CD-4 fans I would like to report that the new demodulator design is complete and now in prototype construction stage. Starting with this posting I will describe the design in detail so that technical and non-technical people should understand. The papers are in PDF format and look the best on screen at 125%. They print at 100%. You will find them by clicking on the link http://www.johana.com/~johana/dorren
Enjoy!

Lou Dorren

Hello,
now, after having placed my preorder for your CD-4 demodulator I wonder if the unit will be equipped with a multi voltage power supply?? Non-Americans have a problem with 120 V ac!:mad:@:
Cheers
C. H. Banfield
 
PLEASE NOTE: This thread concerns Lou Dorren's new demodulator. Please stay on topic.

I have moved the ongoing CD-4 Technical Discussion that started in this thread to its own thread located here:

https://www.quadraphonicquad.com/forums/showthread.php?14659-CD-4-Ramblings-and-Tech-Discussion

https://www.quadraphonicquad.com/forums/showthread.php?14659-CD-4-Ramblings-and-Tech-Discussion

You can all continue in that location as you must.

Anything left in this thread that does not concern Lou's demodulator will be deleted. Thanks for playing.
 
Hello QQ Members,

As you’ve heard from Jon Urban, the last six weeks have been very difficult for me. I lost my right-hand man, Michael Flaherty, to liver cancer. He apparently was sick for awhile and didn’t know it, and by the time he was diagnosed it was to late and he deteriorated over four weeks. All of you know him as WA6UBW and he has been my project coordinator for both electronic and music projects. Here on the QQ site he was responsible for keeping tabs on the number of CD-4 demodulators that people wanted, the extra cartridges and extra styli. He is proving to be a tough man to replace, but I have, in fact, a candidate that I will introduce everybody to in the next week.

During this project, I have lost two very good friends—Cai Campbell, whom I knew from the Quad years and Michael, whom I knew for almost 35 years. Because these two people were great CD-4 quadraphonic enthusiasts, I wish to dedicate the new CD-4 demodulator to their memory. I appreciate everyone’s kind words about Michael and I also appreciate everybody’s patience, as I know this project has taken awhile. I am bringing some extra help up to speed so we can get to the next stage of this project. I will post to this forum when unit has been shipped to John Urban, which will be very shortly.

Lou Dorren
 
The axial tilt cancellation circuit on the Audionics S&IC does not affect phase in any way. It corrects electronically for any tilt error which reduces separation. It does so by mixing in a small amount of the opposite channel inverted. This causes the cancellation of the leakage. What is commonly called 180 degrees out of phase is not actually out of phase at all, it is just inverted. With a sine wave signal it resembles a condition of being 180 degrees out of phase so much that it came to be called that, but with an irregular waveform as such with audio, real 180 degrees out of phase audio would not do the trick.

The Quadfather
 
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