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

[Quadro-Action]

Hello Lou, it may be, that some nervous fans like to know at first the result of the test report from John Urban before they make an order for the demodulator. If those will ask me, I like to ask you already now: Is it possible to buy a demodulator also after the usual time for registration or by general later time (for excample if they have to pay actual their new car?) This may be also interesting for any unsured fans in the states. I self belong of course to those, who have make an order actual, as you may have already noticed.
Dietrich

 

[Cai Campbell]

As much as it pains me to say this, I can't wait to put my JVC CD4-50 away into the closet. Yes, I have this level of expectation and that much trust in Lou!

Ohboyohboyohboyohboy!

:51banana:

Gee, I wonder how how many CD-4 conversions we'll see after this thing is released?

 

[Lucanu]

And how many price lift-ups on cd-4 records on ebay?

 

[The Quadfather]

Even if this demodulator does not perform better than the legacy demods, it will be made with modern parts that will not be obsolete any time soon. How long will the industry keep making those phase locked loop chips common to most designs? Though I will have reservations about retiring my well performing 4DD5, I will buy the new demod for this reason only. Any improvement in performance I get will be pure bonus.

The Quadfather

 

[Malcolm2010]

Quadfather,
Lou stated in a reply to me that the PLL chip is proprietary. This maymake it nigh impossible to get once supplies are exhausted.

Malcolm


Quote

Lou,
What PLL chip are you using? the PDF image is a little fuzzy.

Thanks

Malcolm

Malcom2010,
Malcom, it is a custom chip I had made for another project. It's number is XY4240.

 

[loudorren]

Hell to all CD-4ers,

Quadfather and Malcom2010,

I am working up the service kit. It will be complete as soon as the pre-production prototype is fully operational and has been in Jon Urban's hands for verification. The kit will be complete and you will be able to purchase extra ones if needed. As it gets closer to production, I will post the service kit price and have any one who wants one indicate so.

Lou Dorren

 

[The Quadfather]

Hmmm, Proprietary, not good. I reckon I better get some extra chips. Are there any other parts that will be proprietary? We need to know.

The Quadfather

 

[loudorren]

Hello CD-4 Quad People,

Quadfather,

Don't let the proprietary scare you. The PLL chip costs $2.00 each. The other proprietary chips might be the programmed filters. They are off the shelf chips but I have to program them. Again the service kit price will be quite reasonable.

Lou Dorren

 

[kfbkfb]

Regarding the CD-4 disc
main channel/base band/sum signal delay:

http://www.aes.org/e-lib/browse.cfm?elib=2752
The sum signal on CD-4 discs is delayed
40x10^-6 seconds compared to the FM based
difference signal.

Does the 2008 CD-4 Demodulator with the
specified phono cartridge compensate for
this delay?

Kirk Bayne

 

[Clemens]

Dear Lou,
Just spent my Saturday evening reading 22 pages of this thread.
Very interesting.
Thank you for providing a new CD-4 demodulator.

All of my audio equipment is silver but I will order the demodulator although its colour is black

Regards from the Netherlands.

Clemens
www.quadrafonie.nl

 

[loudorren]

Hello to QQ people all,

kfbkfb,
Kirk, The answer is yes. All CD-4 demodulators, old and new must compensate for the 40 usec delay to get the best separation Front to Back for the Left and Right composite channels.

Clemens, Welcome aboard the thread. If you have not yet, you might download the 5 installment paper on the new CD-4 demodulator. You will find it at :

http://www.johana.com/~johana/dorren

With regards to the color, like Henry Ford said about his model T automobile "You can have it in any color you wand as long as it is Black*,

Lou Dorren

 

[Clemens]

Clemens, Welcome aboard the thread. If you have not yet, you might download the 5 installment paper on the new CD-4 demodulator. You will find it at :

http://www.johana.com/~johana/dorren

With regards to the color, like Henry Ford said about his model T automobile "You can have it in any color you wand as long as it is Black*,

Lou Dorren

Lou, thanks I found the papers already.
Success with the development of the demodulator.

Clemens
www.quadrafonie.nl

 

[kfbkfb]

Regarding an all software CD-4 Demodulator:

(This has been mentioned from time to time
in this discussion forum)

http://comsec.com/software-radio.html
An FM "radio" has been developed, it seems like
the FM demodulation code could be adapted to
work with the CD-4 FM based difference signals.

The only remaining CD-4 specific functions that
would need a software implementation are ANRS
decoding and the muting system.

Kirk Bayne

 

[The Quadfather]

I reckon at two bucks a pop, I can afford to stock some extra chips.

The Quadfather

 

[Doug G.]

Software demodulation or decoding might be cool but they're not 1/100th as cool as honest-to-goodness electronical types.

Doug

 

[surroundophile]

And how many price lift-ups on cd-4 records on ebay?

Its already started. As soon as Lou announced the demodulator, I started adding to my collection. And I've seen prices go up for some of the less common ones.

 

[loudorren]

Hello Quadraphites,

kfbkfb,

Kirk, The basic GNU FM algorithm is not good enough for CD-4. It must be modified to demodulate FM-PM-SSBFM. This adds a significant amount of processing. It is possible to use only the FM demodulation algorithm alone, however the midrange and high frequency separation will suffer.

Sometimes you can do things better in analog than digital and sometimes visa versa. The best approach is to use the strengths of both to optimize the end result.

Lou Dorren

 

[The Quadfather]

Hey Lou:
You say that additional amounts of processing are required to handle the different levels of modulation that are different for different frequencies, I assume for the purpose of this question: Do the legacy demodulators compensate for this, or was this one of the cost compromises? I know most of them use a basic PLL chip that was widely used for FM demodulation in hobbyist projects at the time, suggesting that this chip was very basic. There really doesn't appear to be much except the ANRS. Not being in on the design, it's hard to know the purpose of every resistor or capacitor. I know that I sometimes look at my own circuit designs and see a particular part and think that if I hadn't designed this thing myself, I wouldn't know what that particular part is intended to do. Some functions are subtile.

The Quadfather

 

[loudorren]

Hello CD-4ers,

Quadfather,

To support my statement "Sometimes you can do things better in analog than digital and sometimes visa versa. The best approach is to use the strengths of both to optimize the end result" here is a case where analog is better. The Phase Lock Loop has some very unique and interesting properties. First, by the use of properly designed loop filters it can accurately track an FM-PM-SSBFM signal.

This was part of my original patent for the CD-4 PLL demodulator. In this case one well designed Integrated Circuit can do better than lines and lines of DSP code and do it cheaper.

Just the opposite is true when it comes to filtering. The program, though quite complex for the filters yields much more accurate filters then does analog.

Both techniques are used in the new CD-4 demodulator!

Lou Dorren

 

[Clemens]

Dear Lou,
A few questions related to the stylus.

Some people are using two turntables, one only for CD-4 records and the other one for stereo, SQ, QS etc. records. I assume this is to obtain maximum lifetime of the Shibata stylus. I am using only one turntable (Technics SL1300).
Can I use your new Shibata stylus for all records? Or is it better to use it for CD-4 only? What is your recommendation?

Have you carried out any tests using Shibata needles for stereo records? What was the outcome?

In post #395 you are writing “QSI record cleaner works differently by emulsifying dirt on the record surface and using the playback stylus as a scoop to actually remove the dirt."
This means the Shibata stylus will scoop and remove the dirt?
Would this not damage the stylus and/or reduce its lifetime?

Thanks,
Clemens

PS
Do you have any test record left over or are they all sold through Ebay? (I missed that)