What's New at QQ?

This is a learning curve for me, but I think I'm getting the hang of how this page will work. I think it will be pretty useful actually. What I'll do is take important posts from the forum, as well as articles from the web and even original content, and they will go on the home page. This will be a reference of sort, a place to start for newcomers, and hopefully it will evolve into something impressive.

It will take time, and you'll just have to hang in there for all of this. I haven't really touched the forum software in years, so it's a learning thing for me again, like a rewind and reset of my brain.

Anyway, I think I have the premissions set now. So keep your eye on the home page, as I'm sure it will change and evolve over the next few months.

Beginning Quadraphonics - by The Quadfather:

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

Ok. I'm not a tech I know just enough to be dangerous, I come at this from the music
end so in simplistic terms here goes. A little history
on the thing (matrix quad) is in order to help the quadraphonicly
challenged. In the early 70's quad was ballyhooed as the next
logical step for audio. We started with mono then stereo so the next
logical step was quad. Sounds good but the problem was
that the technology was weak (matrix quad) and had not
developed enough to make it work as ballyhooed. Notable
exception was the quad reel to reel which was simple
enough cause 4 channel recordings (4 discrete channels) would be played back
on 4 channel play decks made for home use . The major record labels
saw this as they saw stereo, (eventually) when mono was it, as the next
logical step. The problem was that lp's were the media
of the day just as disc's are now. So how were they
going to get 4 channels out of a media that was great for
two channels (there is only two walls on a record
groove) there was two ways, one way was a discrete way using two bands in
the grove wall, one above
the other. The upper band holding the rear channel info called CD-4. CD-4
was developed by JVC/RCA. It was a pain in the ass to get to work well,
needed a special cartridge and a demodulator to get the rear sound.
Every thing had to be adjusted just right to get it to work and the
records tended to ware fast on most systems. My cd-4 set up works nice by the way.



Another way (actually the first way developed) was a matrixed way.
Matrix in it's simplest form is to
reverse your rear speakers. This is not quad but goofed up stereo x
2. I say this because many folks were turned off of quad by cheap
modular quad setups that did just that. In 1968 Peter Scheiber
invented a discrete circuit using caps and resisters to matrix out of
phase signals in recordings. The algorithm he first used, only
achieved 3 dbs of separation all the way around but was the base
for early quad decoders like the EV-4 (ElectraVoice) and the DynaQuad (Dynaco).
When these units hit the market there was a resounding thud! They were a step back
with only 3 dbs of separation front L-R, it was like mono x 4.

But, Benjamin Bauer, at CBS saw some thing there and developed a way to
get 20 dbs of separation front L-R and the same 3dbs the rest of the
way around. Still using a discrete circuit. Still pretty lame but at
least it's not mono x 4. He called it SQ (Surround Quadraphonic).
At the same time Isao Itoh of Sansui was developing a very similar
system which Sansui named QS(Quadraphonic-Stereo). They were
actually first with the QS-1 in 1970. They went at it differently
Sacrificing front channel separation for diagonal separation (same 20
dbs) but it sounded more quad

Bob that is what is in your QS-800 The stated separation is 20dbs
diagonally but I think the other post is right, it was more like 10 to 13
dbs and only 3 dbs front L-R. This is what is in all the QR and QS
units plus the early and lesser QRX units like the QRX-3000
and the QRX-5500. These should be called
first generation Sansui QS units. And to clear up one of my earlier
posts, there were two versions of the QRX-5500, there was an "A"
model (QRX-5500A). It is different in that it was a hybrid of first and
a second gen. Sansui quad units (more in a moment).
In 1974 Sansui unveiled the second generation QS decoder built into
the 7001. “The” true Variomatrix system. What was new was the ic.
They invented some chips to get more separation. At the same time
CBS was working on improving the SQ system with some chips and
did actually produce some units that are ultra rare now. It had similar results
as the Variomatrix but went at it a different way.
The chip Sansui invented used oral masking to get separation. Oral
masking is the principle that two sounds, one played louder than the
other, the louder signal is what you hear. The softer is masked by
the way our mind reacts to sound. So here’s kinda how it works, this
is after the basic decoding is already done on the out of phase
signals (the diffuse sounding stuff that doesn't seem to be coming
from one speaker). The Sansui chip looks for the loudest signal
and amps it a little at the same time masking it
in the other channels. This is done very fast by the IC and makes it
sound very discrete. This scheme achieves 20dbs front L-R (as good as
many decent carts) and the same front to back and back L-R but the
diagonal separation was 35dbs, VERY QUAD! 35dbs of separation is
better than just about any cart and good enough to sound almost discrete to your brain.



There are three chips on the quad board in the Sansui 2nd gen. units
and only two in the QRX-5500A. The 3rd missing chip step was still
handled by a discrete circuit. Because of this the front to back and
back L-R separation was only about 10 dbs. This hybrid board is also in
the 7500A. The QRX 5001, 6001, 7001, 8001, 9001, 777 and the
999 as well as the QSD-1, D-2 and D-1000. All had second gen boards.

Up to this time the other manufacturer were concentrating on SQ
decoding because CBS wanted it that way (their format) and because
they had many more titles. So a standard was never chosen in the US
but in Japan QS was chosen as the standard quad format even though
JVC had CD-4. SQ (CBS) wouldn't submit their format to the
determining board (format war). The best the other manufacturers
could come up with were logic circuits for decoding (Pioneer,
Kenwood, Sony so on) not much better then first gen. Sansui quads.
Sansui was way ahead of their time! Not until 1979 did Jim Fosgate
come out with the Space and Image Composer (later stripped down and
called the Tate II) that did for separation on SQ what Variomatrix
did for QS but that is a whole other story.

Alas quad was dying in 1975 due to the format war (sq vs qs vs cd-4)
and lame decoding just when these guys were getting it figured out.

So 20 dbs of separation all around (like a decent cart.) and 35 dbs
diagonally for QS encoded material, very quad! Almost as discrete
(to your brain) as 4 channel tape (rtr & quad 8track). Again, this
is with a good cart; that is setup correctly. If the cart has only
16 dbs of separation then every thing is reduced.
That's great but who has QS encoded records (me about 45 or so) and
what did come out is old now (there was some great stuff though like
Pink Floyd, Steely Dan, Joe Walsh to name a few). So what's the big deal?
Variomatrix in the quad synth mode gets the same results from stereo
material! Stereo material that is recorded using a lot of complex
phasing makes the Variomatrix system sing! And now with the one's
and zero's of the digital age via the cd, stereo separation is
discrete so the decoding is better now then Sansui ever dreamed. For
example, remember Thomas Dolby's "She Blinded Me With Science"? Very
complex phasing technics in the mix, he was quite the wizard. This
cd sounds so quad as to rival PF's DSOTM that Alan Parsons mixed
with quad as the format. The stereo version of DSOTM was mixed down
from the quad masters. So any thing by Alan Parsons, Steve Miller,
Rush, Hendrix on and on, any one putting out of phase stuff in their
recordings, the variomatrix circuit eats up! This would include just
about every thing recorded now.

Just about every thing goes better with Coke er Variomatrix!

My QSD-1 (standalone high end decoder) has three sets of quad
boards for the three bands, bass , mid, treble so it can perform the
oral masking on three things at the same time, say low bass or
drums, midrange- guitar, vocals so on and any thing out of phase on
the high end. End result is smoother but barely noticeable in a
blind fold test.

Sansui quad hybrid owners don't despair! They were better then any
thing else by far and are great still at synthing quad, the
QRX-01 units were just better. Which makes me wonder
why any one buys any thing quad on ebay other than Sansui?



Well there you have it more then you then you ever wanted to now
about Sansui quad.

Thanks to QB and others for the education over the years! :worhty

Dave

Todd is God, KINDA!