Yes, had one as a teenager. It did both quad LP's and quadrophonic 8 tracks. Those used both channels of track 1 and 3 or switched to track 2 and 4. Probably the only case where 8 track was higher fidelity in the sense of 4 channels. The LPs often had very little channel separation in 4 channels.
https://www.ajournalofmusicalthings...l-trying-to-make-a-comeback-it-looks-like-it/
Is quadraphonic vinyl trying to make a comeback? It looks like it.
PROBABLY MORE THAN MOST WANT TO KNOW ABOUT QUAD BUT HERE GOES:
I only experienced the LPs. I guess that I had a really good (for my DUAL 1229Q TT) cartridge stylus assembly and a good quad decoder at the time because both my friends & I still talk about the good separation I had. I still have a number of very pristine quad albums from then but no decoder or DUAL 1229Q TT. (The DUAL that I currently own is a standard 1229).
PANASONIC/TECHNICS, JVC, SHURE, and others made some very good quad specific carts.
Examples:
The legendary Matsushita/Panasonic EPC-451c 4-Channel cartridge. The EPC-451c is a Strain Gauge semiconductor disc transducer electret condenser cartridge, based on a technology far different than conventional cartridges; consequently, this cartridge requires a Panasonic or Technics CD-4 demodulator , which supplies voltage to the cartridge, then reads the output formulating the discrete signal into four channels. Fitted with the correct stylus and attached to the demodulator described above, the EPC-451c has an astounding 10Hz - 50kHz frequency response, tracking at 1.7-2.3 grams with a 3.8 gram mass.
JVC X-1
Motor: moving magnet (samariam cobalt)
- Stylus: Shibata
- Cantilever: Beryllium
- Output (1kHz, 5cm/s): 2.7mV
- Balance: Less than 1dB
- Channel separation: >25dB (1kHz), >20dB (30kHz)
- Impedance: 470Ω + 342mH
- Load: 47k to 100k
- Optimum tracking weight: 1.7 ± 0.15grams
- Frequency response: 10Hz to 60kHz
TECHNICS, the: 450c; 451; and the 460. These cartridges are all semiconductor, displacement-sensitive types. All are very expensive today and require a special preamp but, no doubt, these provide a unique, wideband transducer, far removed from today's technology.
The SHURE M24H has a high -efficiency magnetic
structure like that of the M95ED, although its
winding inductance is considerably lower because
of the necessity for a 50,000 -Hz frequency
response. Also, its hyperbolically
shaped diamond stylus has, according to
Shure; the lowest tip mass (0.39 milligram) of
any CD -4 cartridge. The hyperbolic tip shape
is Shure's equivalent of the Shibata and similar
special styli that are designed to trace ultrasonic
frequencies without causing excessive
record wear.
The M24H is designed to track at forces between
1 and 1.5 grams, with 1.25 grams being
the recommended value. Its frequency response
is essentially flat up to about 10,000
Hz, rising at higher frequencies to a maximum
at about 30,000 Hz (the CD -4 carrier frequency).
Because of its low coil inductance of 160
millihenries, the cartridge -loading requirements
are somewhat different than for other
Shure cartridges (which usually give their flattest
response when loaded with 400 to 500 picofarads
of capacitance). In stereo operation,
the M24H can be loaded by a 20,000- to
100,0000 -ohm resistance in parallel with a capacitance
of 100 to 250 picofarads. For CD -4
service, the recommended load is the standard
100,000 -ohm input of a CD -4 demodulator
paralleled with not more than 100 picofarads.
What about moving-coil phono cartridges?
Moving-coil (MC) phono cartridges and CD-4 records seem to have passed each other in the revolving door of fashion. By the time the dominance of the moving-coil type cartridge was established the upper end of the phono pickup market, CD-4 was well past its acme, and hardware demodulators rarely (if ever) seem to provide a suitable front-end amplifier for MC cartridges.
Similarly, in a comprehensive review of a group of MC cartridges from just after the heyday of quad1, a review which includes testing of extended frequency response and crosstalk, no mention is made as to the suitability of the various products for CD-4: only stereo is considered.
Prima facie, the somewhat higher moving mass of the moving-coil armature over a moving-magnet type does not naturally favour this cartridge type for the high-frequency tracking required in recovering the CD-4 subcarriers. Nevertheless, the low output impedance of the moving-coil pickup sidesteps the troublesome issues of cable capacitance and loading which adversely affect the performance of the moving-magnet type for CD-4.
Certainly, MC cartridges exist which would suit CD-4 records with stylus resonances high enough to keep response and crosstalk under control in the frequency range of CD-4 difference information. Indeed a couple of models in reference 1 demonstrate suitability. (Although, interestingly, not the model from JVC - the MC-2 - which is most unsuitable. This model superseded the MC-1 which had a Shibata stylus and a frequency response to over 50kHz. So, it seems CD-4 was truly dead even for JVC by 1979).
Cartridge aside, a real issue with moving-coil pickups for CD-4 lies in the need for greater voltage-gain. This is typically achieved with extra preamplifier stages or step-up transformers prior to the normal RIAA equalizing circuit. In either case, the bandwidth of this extra gain-stage is often curtailed. Transformers rarely offer a flat frequency-response greatly beyond the audio band, and all-electronic MC preamplifiers often employ deliberate bandwidth restriction lest the pickup becomes sensitive to radio frequencies (RF).
The CD-4 format demands a transducer bandwidth some three times greater than that required for normal records and this requirement is rarely a consideration to the modern designer who is more concerned with establishing immunity to mobile-phone (
GSM buzz) signals and the like. In addition, few historical hardware examples exist of MC type pickups for CD-4. The Ortofon SL15Q is a rare example. So, considerable experimentation is required to determine if a MC cartridge and preamplifier are suitable for CD-4 needle-drops.
But, of course there was the confusing FORMAT WARS (with some being definitively better than others) [and tapes had there own separate FORMAT WARS]:
Matrix (4-2-4) formats:
With matrix formats four channels are converted (encoded) down to two channels. These are then passed through a two-channel transmission medium (usually an LP record) before being decoded to four channels and presented to four speakers. To transmit four individual audio signals in a stereo-compatible manner, there must be four simultaneous linear equations to reproduce the original four audio signals at the output.
These systems used
matrix decoding technology to recover four channels from the two channels recorded on the record. Matrix systems can have a significant level of channel independence but not full channel separation.
Matrix quadraphonic recordings can be played in two channels on conventional stereo record players. There are varying levels of stereo and mono compatibility in these systems. The term
compatible indicates that:
- A single-channel (mono) system will reproduce all four audio signals in its one speaker.
- two-channel (stereo) system will reproduce the left front and left rear audio signals in the left speaker and the right front and right rear signals in the right speaker.
This 4:2:4 process could not be accomplished without some information loss. That is to say, the four channels produced at the final stage were not truly identical to those with which the process had begun. In order for the effect to work as intended a recording engineer needed to be specially trained for working in each of these formats. Special mixing rules for matrix recording minimize the technological limitations inherent in matrix formats and mask or eliminate undesired side effects.
EV-4/Stereo-4 and Dynaquad (DY):
The first of these were basic systems with relatively poor performance developed by
Electro-Voice (
EV-4/Stereo-4) and
Dynaco (
Dynaquad (DY)). A so-called
matrix format, it utilized four sound channels which were "encoded" into two stereo album tracks. These were then "decoded" into the original four sound channels. But with poor decode performance, these systems failed to match the accuracy or channel independence of later matrix formats.
The original systems (DY and EV-4) suffered from low front left-right separation (around 12 dB) and a poor rear left-right separation of 2 dB. The decoders were designed more to give an effect rather than accurate decoding, which was mainly due to limitations in both systems. Since both systems were very closely related mathematically, users only needed one decoder of either system to playback albums of both systems.
The differences between the early and late matrix systems were so vast, it made decoding DY/EV-4 with either SQ or QS decoders with accuracy impossible; the results often being a "smeared" or poorly defined sound stage, which could be vastly different from what was intended by the producer or recording engineer.
QS Regular Matrix and SQ Quadraphonic:
Improved systems based on
Peter Scheiber's work on utilizing 90-degree phase-shift circuitry came later, namely the
QS and
SQ systems.
The first of these, known as
QS, was developed by
Sansui Electric. A so-called matrix format, it utilized four sound channels, which were "encoded" into two stereo album tracks. These were then "decoded" into the original four sound channels. The QS system debuted in the United States in March 1971 and was improved by their
Vario-Matrix system in 1973.[
citation needed]
The second,
SQ, was developed and marketed by
Columbia Records and
Sony and entered the US market in April 1971. The
SQ format was also used by companies such as
EMI in Great Britain, who pressed several
SQ album releases. The sound separation of the
SQ system was greatly improved by the introduction of
SQ Full Logic decoding in 1975 using the Motorola chips MC1312, MC1314 & MC1315.[
citation needed]
Both SQ and QS had significant support from major record companies and hardware manufacturers during the 1970s. They also achieved notable sales and market penetration. Unfortunately, due to the similarities in name and technology these could easily be confused by the public.
Discrete (4-4-4) formats[edit]
Discrete reproduction describes a quadraphonic system in which all four channels are fully independent of each other. As its name suggests, with
discrete formats the original four
audio channels are passed through a four-channel transmission medium and presented to a four-channel reproduction system and fed to four speakers. This is defined as a 4–4–4 system.
Discrete phonograph systems use a specialized
demodulator to decode four fully independent sound channels. This allowed for full channel separation. Such systems could be prone to reduced record life. However, more durable vinyl formulations were quickly developed to work around this problem and nearly all discrete LPs use special vinyl. When discrete quadraphonic LPs are played on conventional stereo record players the entire music program can be heard in stereo.
CD-4 or Quadradisc
The third major format for four-channel vinyl LPs, known as
CD-4 or
Quadradisc, was devised by the Japanese
JVC Corporation along with its US counterpart
RCA Records.
This quadraphonic format was first marketed in the United States in May 1972. A fully discrete system, it eschewed matrix technologies in favor of a more sophisticated method.[
citation needed] As with stereo records, the system uses 2 main left and right audio channels, and this is what allows CD-4 to maintain compatibility with conventional stereo playback. CD-4 also adds 2 additional "difference" audio channels to the main channels. The difference signals are encoded in
ultrasonic carrier frequencies in the range of 30 kHz, which is above the audible range. CD-4 requires a specialized
phono cartridge with a "Shibata" stylus to read these additional high frequencies. The combined signals are then sent to a special demodulator for four channel decoding. The demodulator converts the ultrasonic signals back into the audible range and uses the difference channels to separate rear audio information from the main channels. Because the CD-4 system maintains four independent signals throughout the process it can accurately reconstruct the intended four channel sound field.
UD-4 / UMX / BMX
UD-4/UMX was developed by Nippon/Columbia (
Denon). This is a hybrid discrete/matrix system. Only 35 to 40 items are encoded in this format and it was marketed only in the UK, Europe, and Japan.
The short-lived system suffered from incompatibility with regular stereo playback due to phase differences between the left and right channels. UD-4 was less critical in its setup than CD-4 because the carriers did not have to handle frequencies as high as those found in the CD-4 system.
Tape formats[edit]
Quadraphonic systems based on tape were also introduced, based on new equipment capable of playing four discrete channels. These recordings are all discrete 4-4-4 recordings released in
reel-to-reel and
8-track cartridge formats. Specially designed four channel machines were required to play these recordings. They are not compatible with stereo players.
Quadraphonic open reel tape (Q4)
A four-channel
reel-to-reel tape unit from the 1970s, one of the few ways to achieve discrete four-channel sound at home
In these systems all four available tracks were recorded on the tape running in the same direction. Pre-recorded four channel reel-to-reel tapes were recorded at 7 and 1/2 inches per second (IPS), which is the fastest speed used for consumer grade reel-to-reel machines. By comparison stereo pre-recorded reel-to-reel tapes have 2 different programs with each running the opposite direction. Many stereo tapes were recorded at only 3 and 3/4 IPS, which is half of the full speed. The slower speed results in significantly poorer sound quality.
Quadraphonic 8-Track Tape (Quad-8 and Q8)
RCA Records followed, in April 1970, with its announcement of a four-channel version of the
8-track tape, named
Quad-8 or
Quadraphonic 8-Track Tape (later shortened to just Q8). These eventually appeared in Sept. 1970.
[13] There were automobile players as well as home versions.
The format was almost identical in appearance to stereo 8-tracks, except for a small sensing notch in the upper left corner of the cartridge. This signaled a quadraphonic 8-track player to combine the odd tracks as audio channels for program 1, and the even tracks as channels for program 2. The format was not backward-compatible with stereo or mono players; although quadraphonic players would play stereo 8-tracks, playing quadraphonic tapes on stereo players resulted in hearing only one-half the channels at a time.
The last release in the quadraphonic 8-track format was in 1978, although most had stopped appearing by the end of 1976.
A pair of APT/Holman PreAmps can be set up for quad synthesis
(I have a pair and can verify this)
Quadraphonic Synthesis
With two Holman Preamplifiers, you can synthesis and control four output channels from just two input channels.
Apply all your inputs to the first Holman Preamplifier. Use it for all your tone controls, filters and source and tape selections. Leave its Stereo Mode in Stereo.
Connect the first Holman Preamplifier's MAIN 1 output to one power amplifier and your two front speakers.
Connect the first Holman Preamplifier's MAIN 2 output to any line-level input of the second Holman Preamplifier.
Connect the second Holman Preamplifier's MAIN 1 output to the power amplifier for your two rear speakers.
Rotate the second Holman Preamplifier's stereo mode control to L-R, and start by setting it to about unity gain or a bit less, and keep its tone controls flat. The tone and filter settings of the first Holman Preamplifier are fed automatically to the second Holman Preamplifier.
Set balance on the first preamp. Set front-rear balance on the Volume control of the second preamp.
Leave the power switch of the second preamp ON, and plug its power cord into a switched outlet of the first Holman Preamplifier. Now the power is controlled by the first Holman Preamplifier, too.