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

[The Quadfather]

Hey Lou:
Regarding the AT440MLa, No, I don't think the cantilever is damaged, I do note that others have reported the sibilance effect. It's not a big (severe) problem, I just turn down the treble, and that supresses it. It just seems to have a peak in the high end. However, separation is pretty good, as good as I have experienced with CD-4, and the demodulation is good, no sandpaper effect. But I intend to buy your demod and cart, so then I will hear what CD-4 should be. However, at this time, I count it as a good deal if I can get distortion free demodulation and good separation so I can enjoy the music. The AT440MLa has given me this.

 

[Quadro-Action]

Hello Lou, meanwhile the tension for the finished demodulator will escalate by the fans - especially for me. But a further interim test-report will be a little sedative pill. I have hope, that you have a technical staff or helpers, so that could built enough items - also for us here in Europe/Germany. I think, you must built more then 10 items !!! Meanwhile I am already thinking over, which of my demodulators I should change for the Dorren-Demod: The JVC 1000, the S 10 or the pretty SH-400??? I hope, my mail will be a further motivation for your impressive project.

Dietrich

 

[kfbkfb]

Regarding the CD-4 Difference Signal
and Narrow Band FM sound quality:

Various sources describe NBFM as having poor
sound quality (suitable for voices etc.).

How is it that (demodulated) CD-4 has such
good sound quality considering that the
difference signal uses a type of NBFM?

Kirk Bayne

 

[Bob Squires Jr]

Dietrich, The answer is simple business. No record company wanted to have dual inventories. Without compatibility, there would have to be a stereo disk and a quad disk. CD-4 allows a single inventory and the stereo listener can buy the CD-4 record and still get great stereo playback.


Lou Dorren

Lou,

Just for laughs, it reminds me of what was written on the labels of the
2 Jethro Tull CD-4 LPs about the producers recommending that this disc be
played only on a CD-4 system that if you wanted stereo that you should get a stereo disk or something of that order!

Count me in for one of your units!
My old Pioneer is dead and an old JVC unit is on it's last leg.

All the best!

-Bob

 

[loudorren]

Hello Quadrabuffs,

kfbkfb,
Kirk, CD-4 is ultra wide band not narrow band FM. To explain this. in the FM modes NBFM, WBFM, UWBFM, the delineation is the ratio of the modulation bandwidth to the carrier frequency. For example in most communications NBFM radio, the modulation bandwidth is from 5 to 15KHz while the carrier frequency can be in the 45 to 54 MHz, 140 to 175 MHz, 220 to 224 MHz, 400 to 512 MHz etc. As can be seen, a 15KHz modulation bandwidth is quite narrow with respect the the carrier frequency. This indicates very small frequency deviation of the carrier (2.5 to 7.5KHz). Commercial FM broadcasting uses WBFM. In this case the modulation bandwidth is 240KHz for a center frequency 88.1 to 107.9 MHz. 240KHz is wide bandwidth and indicates a wide frequency deviation of 75KHz.

CD-4s situation is a little different. First it is a composite of three modulation types, FM-PM-SSBFM depending on modulation frequency. Second and most important is that the modulation bandwidth 18 to 45 KHz or 27 KHz is almost equal to the carrier frequency 30KHz. The ratio of the modulation bandwidth (27KHz) to carrier frequency (30KHz) qualifies the CD-4 system as ultra Wide Band. The deviation for the first modulation type is 7.5 KHz, for the second modulation type .9 radian, and for the third modulation type 2.5 KHz. These are quite large for a 30KHz carrier.

bsquiresjr,

Bob, That's before they knew any better!

Lou Dorren

 

[surroundophile]

In the Hollywood area, where all the movie studios are, they need to keep many vintage machines because of all the old formats that still needs to be worked with. A friend of mine is transferring a 1” 16 track reel into the digital realm and had to locate a production house that could get their hands on one. I’d be surprised if there Was Not a CD-4 mastering machine out there. I’ll ask the production house and a few other contacts if they know of any Quad mastering machines that still might exist.

What did you find out?

 

[surroundophile]

Hello CD-4ers,

I will be brief today and answer most of your questions in my next posting. World wide, when CD-4 records were being produced there were only 5 cutting systems. A 1/3 speed in Japan, a 1/3 speed in Indianapolis, 1/2 speed in Los Angeles, 1/2 speed in Japan, experimental real time speed in Japan. That was it, no others. To my knowledge, none still exist, However, I have sent an email to a good friend of mine to confirm.

Lou Dorren

And the response?

 

[surroundophile]

http://launch.groups.yahoo.com/group/quadraphonicquad/message/1168

Perhaps the contact info with this post still works,
maybe an RCA Quadulator can be located
(and possibly refurbished) and used to create
CD-4 master discs.

Kirk Bayne

Anybody investigate?
I bring this and the other above topics up because they seem to have been forgotten. With the big "rebirth" in popularity of vinyl, maybe we could get some new CD-4 vinyl out of it for us!!

 

[kfbkfb]

Regarding the CD-4 Difference Signals:

Is there a maximum level/frequency graph for the
difference signals (due to preemphasis and maybe
ANRS, I doubt if it's all that flat)?

According to this FM information:
http://www.ycars.org/EFRA/Module B/fmapps.htm
the CD-4 Difference Signal is a type of NBFM (DR<=1).

Kirk Bayne

 

[Old Quad Guy]

What did you find out?

I've been busy and have not found out anything yet, but I might be in L. A. in a few months and will ask around if I’m able to go. A friend of mine is working on tracks with a mixer who supposedly worked on Quad stuff - so I was told. He might have some info or point us in the right direction.

I know we are all just interested to know if they still exist. But if a CD-4 mastering machine could be found, then what? Ideally a project to release the CD-4 Quad material on record again along with a DVD-Audio would be nice. Perhaps a new record label could be formed. I wonder how hard it would be to license Quad material for a release and what the costs would be?

 

[loudorren]

Hello CD-4ers,

surroundophile, As of today there are no CD-4 cutting systems intact in the USA. Still checking in Japan.

kfbkfb,

Kirk, CD-4 is a wide band system. In the FM portion DR, is never less than 1. At 50 Hz modulating frequency with 7.5KHz deviation DR=150. At 500 Hz modulating frequency with 7.5KHz deviation DR=15. At 5KHz modulating frequency with 7.5KHz deviation DR=1.5.
The phase modulation portion of the signal is .9 radian which yields only 1 significant sideband pair and the SSBFM portion has 2.5 KHz deviation but only has the upper sideband from 10 to 15 KHz modulating frequency. The overall modulation index (DR) of CD-4 is controlled by the FM portion of the signal.

Lou Dorren

 

[Doug G.]

Hello CD-4ers,



kfbkfb,

Kirk, CD-4 is a wide band system. In the FM portion DR, is never less than 1. At 50 Hz modulating frequency with 7.5KHz deviation DR=150. At 500 Hz modulating frequency with 7.5KHz deviation DR=15. At 5KHz modulating frequency with 7.5KHz deviation DR=1.5.
The phase modulation portion of the signal is .9 radian which yields only 1 significant sideband pair and the SSBFM portion has 2.5 KHz deviation but only has the upper sideband from 10 to 15 KHz modulating frequency. The overall modulation index (DR) of CD-4 is controlled by the FM portion of the signal.

Lou Dorren

Wow! All I can say is that digital electronics has got nothing on analog for shear fascinating complexity!

Doug

 

[kfbkfb]

Regarding CD-4 Phono Cartridges
and the 20kHz to 45kHz frequency region:

The Technics SA-7300X Quadraphonic Receiver
uses the QSI5022.

On the rear panel of the 7300X there's a 3
position (DOWN NORMAL UP) switch labeled
"30kHz COMPENSATOR".

Considering the limiter range of the QSI5022,
why would the 30kHz frequency region need any
sort of compensation?

Kirk Bayne

 

[Quadro-Klaus]

Hi Lou,
some time ago Dietrich (Quadro-Action) told me, that you are going to build a new CD-4 Demodulator. I was impressed by the idea immediately enthusiastic. Today I read all postings on this subject. I am interested in any case and I know some fans in Germany, Austria and Switzerland, which also certainly want to have one. Please think in the choice of power supply that we have get 220 volts and 50 Hz. I wish every success for further work.

 

[elevatorsfan]

Hi Lou,

Longtime reader, new member. I would like to buy one of the CD-4 demodulators when they become available. Also, are any record cleaning kits still available?

Thanks
Jerry Tomko

 

[loudorren]

Hello Quadratonians,

kfbkfb,
Kirk, Sometimes, no matter how hard you try to explain the futility of circuits (30 KHz carrier compensators, automatic separation circuits, carrier crosstalk cancel) to design groups who have got these circuits glued into their brains, there is nothing you can do to dissuade them!

Quadro-Kluas,

Thanks for the kind words. The power supply is universal, and will work from 100 to 240 VAC 50 to 60 Hz.

elevatorsfan, There ar 30 kits left from the first run.

Lou Dorren

 

[Old Quad Guy]

Hi Lou,
Do you know when you're going to send the cleaning kits out?
Thanks. Jim

 

[wa6ubw]

Please think in the choice of power supply that we have get 220 volts and 50 Hz. I wish every success for further work.

Lou has been crazy busy lately so I'll answer you about the power supply. It WILL be universal... I'll let him give the details when he's on the board.

 

[vinylguy4]

A bit of press on this project in this month's The Absolute Sound, page 8, in the Letters to Editor section. See Time Warp entry.

Next, the mags will be wanting a review sample. (KR?)

vinylguy4

 

[wa6ubw]

A bit of press on this project in this month's The Absolute Sound...

can you give me a hint? I am not a subscriber.