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

[loudorren]

Hello Rolv-Karsten,

It brings back found memories for me of a time long, long, ago, in a galaxy far, far, away (borrowed from Star Wars).

Lou Dorren

 

[winopener]

It brings back found memories for me of a time long, long, ago, in a galaxy far, far, away (borrowed from Star Wars).
Lou Dorren

Something like that? (just got the reel...)

 

[rolvkarsten]

Hello Rolv-Karsten,

It brings back found memories for me of a time long, long, ago, in a galaxy far, far, away (borrowed from Star Wars).

Lou Dorren

Lou et al
Glad you enjoyed it!
RK

 

[kfbkfb]

Another way to create CD-4 master discs:

1. Real time playback of 4 channel master
2. 15kHz LPF of LF, LB, RF, RB
3. LF+LB, RF+RB (delay)
4. LF-LB, RF-RB (ANRS encoding, preemphasis,
modulate 30kHz carrier, bandwidth limit
result to 20kHz to 45kHz)
5. Combine 3 and 4 to create L, R
6. Digital audio recording of L, R
(at least 96kHz 16bits)
7. Play 6 at 1/2 speed into a 1/2 speed
record cutting system

Kirk Bayne

 

[rolvkarsten]

Another one, the "JVC CD-4 AN INTRODUCTION"
http://www.yousendit.com/transfer.php?action=download&ufid=668209C171274324
Read and enjoy:banana:

 

[The Quadfather]

Hey Y'all:
That was a very interesting read. I either had forgotten or never knew about Neutrex and CLC, I'm not sure which. I also didn't know that 1/3 speed recording was employed. It seems that a special playback deck is required. However, that could be eliminated with the use of a digital delay. The undelayed output would take the place of the advance head output, and the delayed output would be the recorded signal. That would allow the use of a standard four channel tape recorder, still commercially available. (Tascam makes them)
As for the Neutrex, I reckon it would still be used today for stereo recording if it improves the main audio. But I don't know.

The Quadfather

 

[rolvkarsten]

I forgot to attach a small jpeg version of the front page, just for reference. Here it is, the front page of "JVC CD-4 AN INTRODUCTION"
Still at http://www.yousendit.com/transfer.ph...8209C171274324

RK

 

[rolvkarsten]

"JVC_DISCRETE_4-CHANNEL_RECORD_CD-4_SYSTEM" for download: http://www.yousendit.com/transfer.php?action=download&ufid=DFE64C517CC5D478
in case someone are interrested.

 

[rolvkarsten]

An old catalogue!
Link at http://www.yousendit.com/transfer.php?action=download&ufid=E80200A4546AC44B
(The World of JVC 4-Channel Sound)

RK

 

[rolvkarsten]

A very early 4-Channel document "Introduction_to_JVC_4-Channel_Stereo" is availlable at http://www.yousendit.com/transfer.php?action=download&ufid=99DB87CB59E7F1E6.

Interresting to note pages 3 and 4 where JVC proposes different 4-channel speaker layouts:
* 4-0 speaker system arrangement with four frontal speakers.
* 2-2 speaker system arrangement with the traditional two front and two rear speakers.
* 3-1 speaker system arrangement with three frontal speakers and one rear speaker.
In fact the only real quadraphonic device in this catalogue is the MTR-10M reel-to-reel tape recorder. It has 3- and 4-channel playback, but only 2-channel recording possibility. So one was required to buy pre-recorded reel-to-reel tape.
Not a word about CD-4.
Two stereo amplifiers to be used, no artificial quad, in other words no SFCS or RM (not to mention QS or SQ).

The text mentions that the 3-1 speaker system arrangement (see above) fixes the hole in the middle. Earlier this was fixed by Paul Klipsch, and later by Gerzon's "Trifield" system incorporated in Meridian equipment.

Well, an interresting piece of surround audio history.

BTW, they call the system "quadrasonic".

RK

 

[loudorren]

Hello everyone,

winopener, Thanks for the picture!

kfbkfb, Quadfather

Kirk, Quadrafather, Interesting idea, however, there are a few more considerations. In mastering there are 2 sets of playback heads, the first in advance of the second by the hysteresis(time delay) of the lathe for variable depth and variable pitch control. The head position of the advance head is adjustable for precision positioning. In addition there is Neutrex(Dynagroove) and carrier level control (CLC). Although there is a way to emulate these functions, the problem lyes with the closed loop nature of the cutting system. The variable pitch and depth control as well as Neutrex and CLC are recording velocity and diameter sensitive and must have feedback on exact position of the cutting head on the disk. As the velocity changes with head position, the amount of pre-distortion that is applied to the cutting head is varied. The CLC maintains a 20 dB difference between the peak amplitude of the main channels and the sub-carriers. The pitch and depth values which are determined by disk position and overall recording amplitude are also involved in the CLC and Neutrex variables. I suspect that a system could be designed with todays technology, but the system would still have to be closed loop involving the lathe.

rolvkarsten, Thanks for all the JVC material.

Lou Dorren

 

[rolvkarsten]

Well, Lou, there's still more. here is one about 4-ch broadcasting, mentioning one Louis Dorren ....
I do not have very much more technical stuff. Probably more catalogues. If anyone is interrested though...

RK

 

[rolvkarsten]

An old LP machine
http://www.yousendit.com/transfer.php?action=download&ufid=2F5EB9DD3A348CC8
RK

 

[loudorren]

Hello rolvkarsten,

I have never seen that one! The block diagrams are very incorrect however. Interesting.

Thanks,

Lou Dorren

 

[rolvkarsten]

These block diagrams? Could you point out the errors, please?
(Maybe obvious, but I haven't glanced in detail at them at all.)

 

[loudorren]

Hello rolvkarsten,

First, the 4 correct equations are as follows.

0-15KHz Main Sum Channel (LF+LB+RF+RB) Sum for mono listener
19 KHz Pilot
23-53 KHz cosine Sub-carrier 38KHz DSBSC (LF+LB)-(RF+RB) Left minus Right Difference for Stereo listener
23-53 KHz sine Sub-carrier 38KHz DSBSC (LF+RF)-(LB+RB) Front minus Back Difference For Quad Listener
61-91 KHz cosine Sub-carrier 76KHz DSBSC (LF+RB)-(RF+LB) Criss minus Cross Diagonal Difference for Quad Listener

There are two methods of generating the Quad Composite signal. One is a time domain mutiplexer and the other is a frequency domain multiplexer. I will post a diagram of each in the next few days. By the way, the receiver de-multiplexers are the compliment of the transmitter units. The signal that comes out of these two methods is the same, which makes both methods compatible.

Lou Dorren

 

[herby]

There are two ways (generally) of sending a compatible 4 channel signal.
First you need the mono signal (LF+RF+LB+RB) as baseband, and you need the stereo difference 'L-R' (LF-RF+LB-RB) at the cosine of 38kHz.
The two alternates one can have is the choice of where the next two difference signals go. If one puts F-B (LF+RF-LB-RB) at 38kHz sine, the other signal (the second order difference, "criss-cross") LF-RF-LB+RB goes at 76kHz. This is how Lou did it.
If you change the switching arrangements, you switch the later two signals and put the "criss-cross" signal at 38kHz, and the "front-back" at 76kHz. Of course, Lou's is "better" since there is less information (typically) in the second order difference. This means that there is fewer high frequency elements, which makes for better FM radio (multipath) response.
The JVC diagrams have it all mixed up!
p.s. His patent(s) cover both ways of doing this.

 

[rolvkarsten]

Thank you for clarifying, both of you.
RK

 

[loudorren]

Hello rolvkarsten,

Here is the Block diagram for the Time Domain Quadraplex Generator.
Frequency domain version in next post.

Lou Dorren

 

[loudorren]

Hello rolvkarsten,

Here is the Block diagram for the Frequency Domain Quadraplex Generator.

Lou Dorren