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

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Quadro-Action

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Hello Mr. Dorren, nice to read the again interesting part IV. The heightening will be only the real demodulator. To your ask: I think, your cleaning mixture was after the test taken to a part of the vynil compound.

Dietrich
 

winopener

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Better than Dietrich: your cleaning mixture had commercial release, or it is possible as a DIY?
 

loudorren

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Hello all QQ people,

Rolvkarsten, The amplifiers of the CD-4 era were not bad. Homotaxial base and triple defused base high speed bipolar power transistors had been developed and everyone was using them. These transistors were quite fast for power transistors and would yield low distortion (THD, IM, TIM) in a typical amplifier.

PNP power transistors were harder to make, so they cost a lot more than the equivalent NPN type. The universal amplifier circuit was the complementary symmetry op amp configuration. This used a complementary output transistor pair (NPN,PNP). Since the PNP transistors were so expensive an engineer at RCA semiconductor came up with a modified design known as the quasi-complementary symmetry op amp configuration. In this design, there are two Darlington pairs of transistors, with one side being a virtual PNP. In the schematic that I have included with this posting, you can see how the virtual transistors are connected. This configuration makes up 98 % of the analog audio amplifiers. Otala's amplifier is the same basic configuration with the exception that there is an extra differential gain stage. This makes the overall open loop gain higher, making feedback lower for higher gain. Otala set the output stage mode to class A, which automatically lowers the amplifiers TIM and IM distortion. The THD however, did not improve because of the beta collapse of the power transistors.

Beta is the dc current gain of a bipolar transistor. As the current through the transistor increases the beta decreases. This decrease is called beta collapse. Most solid state amplifier designers assumed that Darlington output configuration would correct beta collapse. Darlington beta is measured by multiplying the beta of the first transistor by the beta of the second transistor.

At lower current levels the individual betas may be something like 100. That would give a Darlington beta of 10,000, which is very good. At high current the individual beta of the second transistor can decrease to 3. This is because the second transistor drives the speaker directly. The Darlington beta becomes 300, which is quite poor. This results in rising THD as the output power rises.

The solution to the problem came a few years later when the triple Darlington configuration was employed. With this configuration, at high power, the first two transistors have a beta of 100 each and the output transistor has a beta of 3. The Darlington beta equals 100 X 100 X 3 which is 30,000. This is excellent and will reduce the THD by 20 to 30dB. Other distortions also improve and the amplifier mode can be changed from class A to class AB2 which is much more efficient.

Quadfather,

It is soap box time again! During the original NQRC field trials, we set up two independent double blind tests to determine the average listeners ability to perceive point source imaging, phantom imaging, frequency imaging, and position imaging verses channel separation. One study was done in San Francisco and the other was done in Washington D.C. Double blind protocol means that no one involved in the test knows any information about any of the test. That includes the administrators and the auditors.

The results were that the average auditor could easily determine point source and phantom source position regardless of frequency. Yes, in fact bass is directional. Prove it to yourself. Next time you go to a fireworks display, you will notice that when a mortar explodes to the left or right of you, the bass does not come from a center position. It comes from the location of the mortar explosion.

So how did 5.1, 6.1, 7.1 etc come about. Not by some high technology means. It is technology being driven by business. Speaker manufactures were worried about getting 4 full range loudspeakers in the home. Film sound mixers were worried about mixing dialog using well know phantom techniques because of the training of the personnel in the theaters in setting up the playback system as well as the home users ability to set up a home system.

From this came 4 small satellite speakers with only midrange and tweeter speakers, a sub-woofer, and a dialog speaker. Let me state to all of the Quad people, you can do everything with a discrete Quad playback system that can be done with 5.1, 6.1 and 7.1 and do it better. First you must have 4 full range loudspeakers. If you want low bass emphasis then you want a 4.4 system. That is four full range loudspeakers(30 Hz to 20 KHz) and 4 real sub-woofers(15Hz to 50Hz). A dialog speaker is not needed! If an actor is on the left side of the screen, then that is where his(her) voice should come from. If that same actor walks across the screen the sound should follow the picture, not just come out of the center. All of this is easily done by using point source and phantom imaging. I have mixed many Quad pieces, both music and stories with actors and have had excellent results.

One additional item is playback setup. You all know how time consuming 5.1 etc setup is. The band aid circuits in 5.1 receivers are overwhelming. Quad receivers need none of this. Just four sources, four amplifiers, and four full range loudspeakers. Discrete Quadraphonic sound provides more accurate performance then any 5.1, 6.1, 7.1 systems with simpler hardware and software.

kfbkfb,
Kirk, Why? Discrete Quad FM does everything 5.1 does, only better!

QuadroAction,
Dietrich, Compound work came after, Q540 was born about 6 months later.

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

winopener, I still use the "QSI record Cleaner - For Superior Sound" (That was our slogan) to clean records and CD/DVDs.

Well that is it for now,

Lou Dorren
 

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quadtrade

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So how did 5.1, 6.1, 7.1 etc come about. Not by some high technology means. It is technology being driven by business. Speaker manufactures were worried about getting 4 full range loudspeakers in the home. Film sound mixers were worried about mixing dialog using well know phantom techniques because of the training of the personnel in the theaters in setting up the playback system as well as the home users ability to set up a home system.

Thank you Tom Holman here is one to you
Kiss my a** for f*cking it all up.
 
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quadtrade

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. Let me state to all of the Quad people, you can do everything with a discrete Quad playback system that can be done with 5.1, 6.1 and 7.1 and do it better.

Lou Dorren[/quote]

LOU
we love you :phones :D
 

Old Quad Guy

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I totally agree.

Sometimes I feel that I’m being old fashioned thinking four speakers are best with all the multi-channel DVD-A / SACD discs I listen to. But everything that can be done with 5.1, Quadraphonic can do it as well if not better because of the unique sound field it produces. Quadraphonic is pleasant to the brain as the sound field causes the speakers to disappear from the room with full range sound. For my tastes, 5.1 takes me out of that experience and makes me think about the extra speakers even though they sound cool.

Now don’t get me wrong, I like my 5.1 mixes. Many are really great classics. If fact I’m taking some baby steps attempting to mix new material in 5.0. The extra center channel allows another speaker option to experiment. I consider 5.1, Quadraphonic, Stereo and Mono their own animals each valid in their own right. But my tastes still go for Quadraphonic in the end despite the loads of 5.1 music / movies in my collection.

Many movie 5.1 mixes don’t make sense with actors on the extreme left and right of the movie picture and yet both voices are coming in mono through the center speaker giving you that old fashion “Drive-in movie speaker experience.” Nothing takes you out of a movie experience faster than a bad multi-channel mix. I prefer Lou’s methods for mixing movies as that sounds like a more lifelike experience and the proper way to utilize speakers.

Thank you Lou for everything!
 

ress4278

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So how did 5.1, 6.1, 7.1 etc come about. Not by some high technology means. It is technology being driven by business. Speaker manufactures were worried about getting 4 full range loudspeakers in the home. Film sound mixers were worried about mixing dialog using well know phantom techniques because of the training of the personnel in the theaters in setting up the playback system as well as the home users ability to set up a home system.

Thank you Tom Holman here is one to you
Kiss my a** for f*cking it all up.
Well now, I have to know. Who is Tom Holman and how did he "F" things up?
 

The Quadfather

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Quadfather,
The results were that the average auditor could easily determine point source and phantom source position regardless of frequency. Yes, in fact bass is directional. Prove it to yourself. Next time you go to a fireworks display, you will notice that when a mortar explodes to the left or right of you, the bass does not come from a center position. It comes from the location of the mortar explosion.
Lou Dorren
Yeah, I know this. I have maintained full range speakers since the quad era (JBL 4311 studio monitors) I added a third Sansui AU717 and a fifth JBL 4311 amplifier when 5.1 came out. I also added two Sony 15'' woofers for the bass channel. I could amaze my friends when giving a CD-4 demonstration by telling them that the center speaker isn't even on. They would actually get up and stick their ear to it to prove it to themselves. As far as the bass output goes, it would be cheap to add, and it could always be turned off. I of course wouldn't want it to interfere with bass going to the four channels. That wouldn't be right. But I figure that nsince most of us have that extra bass speaker (or in my case, a pair) it would be nice to be able to use them if we wanted to. But then again, it could be rigged up separately by anyone with technical competence, using the stereo preamp outs you plan to include (low pass filtering would be needed).
 

kfbkfb

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Regarding 2 or 3 (front) channels
in Surround Sound systems:

3 channel RCA(!) Living Stereo
(about 10 years before CD-4):
http://www.highfidelityreview.com/news/news.asp?newsnumber=13365867

Why did RCA like 3 channel (L,C,R) stereo in
the early 1960s, yet was OK with a phantom
center front "channel" in the Quadraphonic
era starting in the late 1960s?

Kirk Bayne
 

loudorren

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Hello kfbkfb,

Kirk,

RCA's living stereo was the first attempt at more than two channels in recording. The center channel was was created from a center microphone.
They had a Left, Center, and Right microphones feeding three independant mono mixers. The output of the mixers fed an Ampex 300 tape deck with a 3 channel head stack on 1/2 inch tape. It first ran at 15 IPS and was later converted to 30 IPS to reduce noise. In the final mix, the center channel was added to the left and right channels at the same level. This made the sound field center heavy. Some liked it, others did not. A compromise was made and they split the difference. At that time, RCA was a major player in home audio, so they added a center speaker to their equipment with a switch and a variable pad to adjust the center speaker volume. Eventually, mixers figured out that the phantom image was as controllable as the point source and they did away with the physical hardware. The schematic I have included shows the RCA Living Stereo 3 speaker connection.

Lou Dorren
 

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winopener

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Probably because 3-track machines were the max multitrack of that era *for recording studio* (Living Stereo are 50's recording!) and for Quadraphonic - which was a *delivery* format - 4-track consumer machines, both as open reel or cart, were easy to produce and market. It made sense to use the two extra channel for rear speakers, thus having the benefit of a full acoustical depth, that use a C channel and leave one out, or going mono on the rear - as Vanguard was doing its first classical quad recording that way.
Hardware stereo compatibility was also something desirable, and it's a lot easier to reroute stereo to 4 channels, doubling front and back, than C and S - you would end up with two speakers that didn't sound at all most of the time.
 

Quadro-Action

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A discussion about the number of channels by recording and reprocution at home will be beneth the demodulator theme also interesting, because a lot of today consumers and engineers means, with 5.1 or more surround they have invented the reel new. So far I know, the first stereophonic experiments have been some years before the stereophonic record has seen the light. There has been attempts to reproduce a stereophonic front line with 5 ore more microphones from left to right in front of an orchestra - direct transmitting to the same number of loudspeakters left to front before a curtain. The same with only 2 microphones left right and only 2 speakers. And the listening result was virtualy the same as such with a lot more technical expense.

By real sterophonic recording for the 2-channel stereo records not only RCA was working with 3 channel tape recorder and microphones, but also Mercury (sometimes also with magnetic coated film) and the british Decca (the Decca tree).
By recording it will be understandable to have many details and facetts of the instruments. And the 3 channel recording technic was in the late 50's the only possible and available technic - beneth the quick later coming 4-channel tape recorder. But I think, that it is an error to mean, the reprocuction at home must be in the same manner as it was recorded. That would mean, that we must today at home have not only 7.1 sets, but those of 30 channels - which is often the number of microphones by today recording. The early RCA experiemnts with the different mixdown of the center channel, as Lou has reported, may be behind the closed doors of the labors (?). But on the sleeves of first living stereo records I have seen only an advertising about their "Victrola" 2-channel music chests or sets.

RCA was working also with their first and early 4-channel machine for the stereophonic records. I think, the additional 2 channels was taken to record more details (similar to the center) but now for ambience or room/hall acoustics.
A nice example for differnt mixdowns and again-again commerzialisation from the same recording source is the "Van Cliburn - Tschaikowsky Concerto No. 1". I have meanwhile the stereo record from 1958, the 2-channel tape, the 4-channel Q8, the 2 channel CD and also the newer SA-CD with 3 channel front information (have they had also in the 50'th a 5-channel machine: 3 front, 2 back?. How to make a 4-channel quadraphonic mixdown from 3 channel? All curious. The same the recording from "Harry Belafonte - Live in Carnegie Hall" with software in different variations in stereo and quadraphonic.

But back to the front informations by reproducing in 2 or 3 channels. I agree with Lou, that the 2-channel reproduction will give a more homogenious sound. And when the sound of an instrument or voice will went from one side to the other (like by the nice recordings of RCA's Stereo Action (The sound your eyes can follow), there may by a separat reproduction of the center instead a steady glide rather little jumps. Of course, each may like also all of the newest technics up to 10.2 , but for me a seaprat center is generally only needed in the cinema with only there possible bad placing situations. And if more and more channels, the acceptance and interess by the many stereo listeners for surround will go lower and lower. But also surround needs the masses. So the quadraphonic technic will also today further on the ideal surround technic. And I wonder, that 3-channel old stereo reproductions on SA-CD are possible, but not from the many 4-channel quadraphonic mastertapes.

So far my comment. If somebody may write additional comments, I am always interested in discussion - bevore we will read the chapter V from Lou.
 

Quadro-Action

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Interesting remark from Winopener about the first quadraphonic recordings and mixdowns by Vanguard. The same methode for quadraphonic surround with only one recorded (and then doubled) rear channel may be taken also from RCA by theire recording of the "Van Cliburn" and the later "quadraphonic" mixdown. That would explain, why there are 5 channels possible from only 4 by recording.

Dietrich
 

winopener

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I've expressed myself badly... Vanguard was doing real quad front and back; the C and S option would had been a great complication for a delivery format in 1970.
About the Van Cliburn - Tschaikowsky Concerto, i can't compare anything, but for the Harry Belafonte concert i think the rear channels are studio-generated ambience/echo or a slightly processed mono ambience channel doubled to rear. It made sense in these early days of quad, since no one would have a ambience extractor or something similar, but today is not worthy. As a sacd Belafonte has seen release in Hong Kong but only as a stereo disc.
 
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Lou,
What speaker placement do you favor? Originally, it seemed, in the corners of a square room was optimal. Now, I read, to stay away from corners. Place the front speakers along the wall in front of the listener and rear speakers to the side. I realize that room dimensions have a lot to do with it, but any “rules of thumb”? Unfortunately, I do not have the time or means to experiment with speaker placement, but I would like to set up a good system soon.

I presently have a “surround” 5.1 setup and find myself turning off the center channel when I listen to music and I have never been pleased with the subwoofer arrangement.

Thanks in advance.
 

quadtrade

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THX ... Tomlinson Holman sold the Apt-Holman preamp and power amp in the 70s, and the preamp was wonderful for its phono stage. He started experimenting (the X) with Dolby Surround equalization, and with the help of the Star Wars crew the rest is history ... for good or for bad.
He was head of Lucasfilms and started us off on this center channel and point one crap. If we can pick anyone who may be responsible for this screwed up 5.1 system we have to deal with now, it is Tom and his THX bogas bullshit.
Tom would srew up a wet dream. Here is one thing we dealt with in late 90s



There is disagreement on the most desirable polar response pattern for the surround channels. The original THX
(Tom Holman eXperiment) home theater specification calls for a dipole pattern. This pattern is quite effective with the
monaural surround sound of Dolby Pro-Logic. The dipole produces a "phasey" sound that is difficult to localize,
adding to the surround effect.


Oh great. He said Lets install more funny stuff like dipole speakers. What an idiot. We dealt with all that crap at shows.
Now he says it should be 10 point 2. Whatever. If he was really been brilliant, he would have stuck with what works if done properly, 4 point 0.
 

quadtrade

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Oh and i will change my tag soon, it probably bothers some people, just need to remind folks every once in a while we can be fooled. SAY TOM HOLMAN!!!!
__________________:smokin
 
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