The board is kinda slow lately so here is some thing to read that I wrote a couple of years ago for a Sansui collector forum. This is a rough history of quad with a Sansui slant that might be helpful for the folks who are coming at this from the back end (Hirez MC). You experts (u know who u are) go easy on my facts, like I said it was rough from the seat of my pants.

BadBob4747@a... wrote:
OK, Fill me in. What is variomatrix quad? I bought my first Sansui
set-up, Sansui 5000X receiver andQS-500 in 1971 in Japan. I used
it for
years. Recently, I got into vintage Sansui stuff and now have an
8080DB and a
QS-800, which match up well with my Sansui 5500X , front and SP-
X7000, rear
speakers. Which units used variomatrix and what makes it superior
to the
older quad units, such as mine. I have always considered quad to
be vastly
superior to stereo. Please educate me. Thanks, Bob

Bob you pushed my quad button, your in for it now!

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.

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 Vatiomatrix 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 is 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