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Beginner's guide to quad

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Reed

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I am new to the quad world, having been born right at the end of the quad era (1978). I have only recently begun exploring the quad world and I am finding that it is far more technical and complex than I first imagined. Does anyone know of a website or book which is a good place for quad newbies to learn the basic of quad in its different formats? Preferably without too much language only an engineer understands? Thanks!

 

mtgc

600 Club - QQ All-Star
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Welcome to the world of Quad. This forum has a great collection of experts on almost every aspect of our love, quadraphonic sound.


MTGC (Michael)
 

The Quadfather

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Hey Reed:
There were several publications that came out in the quad era but they would be hard to find now. I can give you a quick rundown and keep it simple but I warn you, it does get technical.

There were two types of quad equipment. one was tape and the other was LP based systems. The tape systems were:

Reel to Reel- Used 1/4 inch tape 4 track tape. (note that 4 track does not mean the same as 4 channel. The track number referred to the number of stripes of recording that was on the tape. This is important because stereo tapes are also four track. Reel to Reel machines were discrete, which meant that there was no intermixing of channels. This is a desireable quality as you will see later.

The other tape system was eight track. Eight track had a continuos loop 1/4 inch tape in a cartridge that was inserted in the machine. Unlike reel to reel, eight track could be used in an automobile, and there were many automotive quad units built. Eight track did not have a high end that was as good as reel to reel, not that it couldn't be done, but the high speed duplication techniques that the record companies used didn't lend itself to good sound. Still the sound wasn't bad, and the eight tracks were one of the more popular forms of quad and are easy to find. They were discrete and gave good separation. Eight tracks suffered well known maladies. Sometimes the machine would get hungry and eat the tape, destroying it. Other times, the capstan would slip and the tape would drag. With quad tapes there was twice as much tape, amplifying this flaw.

The other main type of quad system was the LP record based system, and was popular because the LP was the highest quality music delivery medium at the time. Some say it still is, and if you ever heard a good LP system with a new record on it you would understand why. Of the LP systems there were two types. Discrete and matrix. There were two dominant matrix systems and only one discrete system. There was also a strange hybrid (UD-4) of the two but it was never dominant, so we will not discuss it here.

Matrix LP systems used an encoder in the recording process. The encoder mixed the four channels down to two, using a fixed special phase relationship that allowed a decoder to decode the original four channels during playback. The encoded signal was recorded on a regular stereo record. The problem with the matrix systems is that it is difficult to extract the original four channels without a lot of crosstalk. the early decoders couldn't do it. Later gain logic circuits were added that improved the situation. The dominant systems were Columbia records' SQ system and Sansui Electronic's QS system. The pinnacle of development for the SQ system were the Tate SQ decoders made by Audionics and Fosgate. Sansui's Variomatrix system was the QS ultimate. Both were very good, but came late in the game, and were still not as good as discrete quad. There were also rans such as Dynaco, Electro Voice and et al.

The other LP based system, CD-4, was considered discrete, and used a modulator during the recording process. There was on the record not only the audio which contained the front two channels mixed in phase with the rear two channels respectively. it also had two supersonic subcarriers that had the front channels mixed with the rear channels out of phase. The left channels were kept separate from the right channels assuring good left to right separation. The supersonic subcarriers were FM modulated with the out of phase audio. JVC's ANRS noise reduction was used on the subcarrier's audio. It was similar to Dolby B noise reduction, and was double ended. A CD-4 demodulator is required for playback, and since the frequency range of the record extends up to 45 KHZ, a special linear contact stylus and a high frequency cartridge is employed. The turntable wiring has to be low capacitance, to avoid killing down the high frequency subcarrier. CD-4 systems have good separation because there are actually four channels recorded on the disc. The demodulator separates the four original channels from the sum and difference signals. This method is the same as is employed in FM stereo radio and TV stereo audio. A demodulator actually is two demodulators one for left side and one for the right. The problems with CD-4 are that the stylus tracking is very finicky, and if it isn't right, it will let you know in very grating terms. But when it is good, it is very good. RCA promoted CD-4 as well as others and a lot of material was produced. CD-4 records were difficult to make, employing half speed mastering which was created for it, because the cutting heads of the time couldn't follow the supersonic subcarriers.

Many pieces of equipment were built, some employing several of these formats, the one exception was reel to reel which was almost always a separate piece of gear. It was common for a radio receiver to have a matrix decoder and a CD-4 demodulator in the same box, and Sansui, especially the latter of, were some of the best. But the best gear were the separate components. Some of the cheaper systems would have an eight track and a turntable and a matrix decoder in the same box, These are to be avoided, for the decoder was usually very poor, and the turntable was usually cheap and hard on records. By buying separate components, you were able to select the best of the best providing you had the cash. Some of this gear can be had for a modest price on Ebay, and some like the Audionics Space and Image Composer (SQ decoder) can sell for a couple of grand. But don't let that discourage you. Armed with this knowledge, you should be able to get started for a modest amount. Happy hunting!

The Quadfather
 

Q-Eight

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Nothin' beats the good ol Q8 for utmost simplicity. If you're an 8-track collector anyway, you know how to overcome the design flaws inherant in the 8-track cartridge.

Nothing beats goin' to a car show, and busting out the Q8 case, popping in Edgar Winter's Frankenstein and freaking out the folks who remember Quad!
 

The Quadfather

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Hey Reed:
If it's Q8 that interests you, then look for an Akai CR80DSS. It is the premium quad eight deck. I believe there is one on Ebay right now. By the way, with old quad gear, you may have to have them recapped, meaning to replace all of the electrolytic capacitors. A lot of this stuff has been in some closet for 20 years, and the capacitors tend to deteriorate when not used. The Akai may need to be rechipped, as well, but it is a fine deck with a strong motor. And it will record in quad. The chips are hard to find, but not impossible. Some of the Akai reel machines use the same chips such as the Akai GX280DSS. It is probably one of the finest consumer reel decks around. It has glass ferrite heads that do not wear out in normal use. They can fail, but they won't wear out. It does have a problem with rivets on the control logic board, but that is fixable. For a beginner, I wouldn't recommend a reel deck unless you want to record party reels or something like that. The pre-recorded reels in quad are expensive and hard to find. However, the opposite is true for eight track. The thing to know about eight track is that you will have to fix any tape you buy if the previous owner hasn't done so. The splice glue tends to dry out and let go, so you will need some splicing tape. this is usually foil tape with an adhesive. it is electrically conductive, and when the foil crosses the track change contacts by the head, the track will change. this tape should be used only at the splice point. any other breaks should be repaired with non foil tape specially designed for the purpose. If the foam pads are shot, then Wingibs can be used to replace them. The wingibs website also sells other tape repair supplies, essential for eight track care.
Incidently, if you want me to write more, you need to ask specific questions for me to answer. I will be glad to answer them in detail.

The Quadfather
 

callmez

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All hail The Quadfather! The first post above is an absolute gem. I eventually figured all of that stuff out, by searching this site, but have never seen it presented so clearly and concisely before. May I humbly suggest to the powers that be (Jon) that it be permanently posted where the newbies can easily find it??

Mark Z
 

Reed

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All I can say is WOW!!! This is a great post and a wonderful introduction!

Right now I am just trying to get my crappy little Teledyne receiver to work. Once I get that fixed and I can play records, then I will start looking for better equipment and an 8-track player.

Thanks for the tip about the capacitors. I think I need to replace some in my receiver. The unit powers on and works great in the left channel, but I get nothing in the right. If I turn it up REALLY loud and push the balance all the way to the right I get the light on the rear right channel to light up like there is a signal rattling around inside the machine, but nothing comes out the speakers. Not even fuzz. I think its time to start checking individual components.

Thanks again!
 

Q-Eight

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For a decent sounding, robust yet afforadable head unit, I'd keep an eye out for the Pioneer QX-9900. Lots of power, nice warm sound, tons of inputs/outputs and it even has pre-outs for EQs and whatnot. Best of all, they can usually be had for around $100. I've had two. They both suffered from burnt out light bulbs, and one had a dead channel. A quick touch with a soldering iron and it was working again.
 

JonUrban

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All hail The Quadfather! The first post above is an absolute gem. I eventually figured all of that stuff out, by searching this site, but have never seen it presented so clearly and concisely before. May I humbly suggest to the powers that be (Jon) that it be permanently posted where the newbies can easily find it??

Mark Z
DONE! Thanks to the original "QuadFather" for taking the time to lay this all out. This thread is now "sticky'd" at the top of this section.

GOOD JOB ALL! :banana:
 

The Quadfather

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Hey Q8Repair:
By recommending the Akai, I'm certainly not discounting any other deck. But however, the Akai is about as serious as it gets. It has four VU meters, it records in quad, it has an AC motor that's built like a reel to reel motor. It sounds good too. And it will make a fine recording if you use good tape. The chips tend to get noisy, but that is a problem of age more than anything. However, you are free to discuss the merits of the Technics deck. I'm sure it's a fine deck, as most technics stuff is pretty good. But I have no personal experience with that deck.

The Quadfather
 

Q-Eight

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I have a Technics 858 and it's a shame it wasn't built with it's little brother 845's latching mechanism and motor. My 845 will play anything, the 858 drags on anything except the tapes with light tension. You can actually watch the lights on the VU's dim as the motor bogs down.
 

Q8Repair

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Messages
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But however, the Akai is about as serious as it gets. It has four VU meters, it records in quad, it has an AC motor that's built like a reel to reel motor.
The Technics deck has four VU meters also, and also records in quad. Plus it's 21" wide. :D Not sure how 'big' the motor is though.
 

carlane3

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Here is a book by Ken sessions that is really interesting on ebay now.

Item number: 170126865820


I am new to the quad world, having been born right at the end of the quad era (1978). I have only recently begun exploring the quad world and I am finding that it is far more technical and complex than I first imagined. Does anyone know of a website or book which is a good place for quad newbies to learn the basic of quad in its different formats? Preferably without too much language only an engineer understands? Thanks!

 

carlane3

Well-known Member
Since 2002/2003
Joined
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Messages
173
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What is does explain is the concepts behind matrix/discrete decoding-encoding methods and the principles behind them which didn't change over the years like equipment did. I read it in college quite a few times...makes for enjoyable reading .

Thanks. Unfortunately, the publication year is 1973, which, if I unserstand correctly, predates the better gear.
 

Cai Campbell

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What is does explain is the concepts behind matrix/discrete decoding-encoding methods and the principles behind them which didn't change over the years like equipment did. I read it in college quite a few times...makes for enjoyable reading .
I have this book and it is a great resource for understanding quadraphonic technologies. Reed, it was never meant to be a guide for purchasing equipment, although it does make reference to, and include pictures of, equipment from the day.
 
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