US3911231A - Four-channel stereophonic reproducing system - Google Patents

Four-channel stereophonic reproducing system Download PDF

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Publication number
US3911231A
US3911231A US471827A US47182774A US3911231A US 3911231 A US3911231 A US 3911231A US 471827 A US471827 A US 471827A US 47182774 A US47182774 A US 47182774A US 3911231 A US3911231 A US 3911231A
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United States
Prior art keywords
channel
sub
signals
capacitor
muting circuit
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US471827A
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English (en)
Inventor
Yukio Sugimoto
Makoto Okamasa
Toyoshi Fukumura
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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Filing date
Publication date
Priority claimed from JP6193673U external-priority patent/JPS5136481Y2/ja
Priority claimed from JP6193773U external-priority patent/JPS5123285Y2/ja
Application filed by Matsushita Electric Industrial Co Ltd filed Critical Matsushita Electric Industrial Co Ltd
Application granted granted Critical
Publication of US3911231A publication Critical patent/US3911231A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S3/00—Systems employing more than two channels, e.g. quadraphonic
    • H04S3/006—Systems employing more than two channels, e.g. quadraphonic in which a plurality of audio signals are transformed in a combination of audio signals and modulated signals, e.g. CD-4 systems

Definitions

  • ABSTRACT Filed: May 20 1974 A four-channel stereophonic reproducing system for reproducing CD-4 type four-channel records.
  • the muting circuit provided in the sub- M 25 973 J 48 61936 channel signal processing circuit is not immediately ay 1973 1937 rendered inoperative lest a large d-c level change take May dpan place at the output side of the detector resulting in production of a loud foreign sound from the loud 5" speakers.
  • the muting circuit is gradually made inoperative after appearance of the [58] Fleld of Search 179/1001] sub-carrier wave of the sub-channel signal. Also, a
  • 1 four-channel record can be reproduced as a twochannel reproduction with passage of the sub-channel [56] UNnE S r S rENTS signals blocked through operation of a select switch.
  • This invention relates to four-channel stereophonic reproducing systems for use in reproduction of CD-4 type four-channel records. Its object is to provide a four-channel stereophonic reproducing system which minimizes foreign noise and sounds that tend to be produced when playback of a record is started. The system also permits reproduction of a four-channel record as a two-channel reproduction.
  • a composite signal obtained from a first main channel signal constituted by a sum combination of first and second audio signals and a first sub-channel signal constituted by a frequency or phase modulation of a difference combination of the first and second audio signals on a predetermined sub-carrier is recorded in one sound groove
  • another composite signal obtained from a second main channel signal constituted by a sum combination of third and fourth audio signals and a second sub-channel signal constituted by a frequency or phase modulation of a difference combination of said third and fourth audio signals on a predetermined subcarrier is recorded on another sound groove.
  • the composite signals are first reproduced by a pick-up, and then the main channel signals and sub-channel signals are separated by filters or the like. Then, the sub-channel signals are detected, and the detection outputs and main channel signals are combined in matrices to derive separate front and back left and right signals.
  • the subchannel signals are frequency modulation or phase modulation signals of very high frequencies, it is likely that they will not be reproduced with fidelity and may be interrupted by such cause as the wear of the pick-up needle tip resulting in a loud foreign noise sound.
  • the muting circuit is immediately rendered inoperative, and also at the same time the pick-up output is suddenly increased. Therefore, a large d-c level change results at the output side of the detector, and this change is passed through the muting circuit to the loudspeakers resulting in the production of a harsh foreign sound.
  • this type of four-channel stereophonic reproducing system is generally capable of reproducing two-channel stereophonic records as well as four-channel records, if it is used for reproduction of a four-channel record with only two speakers (as in reproduction of a two-channel record) only front signals or back signals will be reproduced. This is a great inconvenience. Accordingly, for an audiophile who is inclined to first purchase only a four-channel stereophonic reproducing system and two loudspeakers and subsequently purchase the additional two loudspeakers when he has obtained the extra money required, a system is desired which permits reproduction of a fourchannel record as a two-channel reproduction of sufficient quality to provide good listening even with only two loudspeakers.
  • the present invention is directed to solution of the above in that and it provides a four-channel stereophonic reproducing system, in which generation of the afore-mentioned foreign sound is eliminated, and which provides a sufficiently listenable reproduction of a four-channel record as a two-channel reproduction.
  • FIG. 1 is a block diagram of a four-channel stereophonic reproducing system embodying the invention.
  • FIG. 2 is a circuit diagram showing a specific circuit construction of part of the same embodiment.
  • reference numeral 1 designates a pick-up
  • numerals 2 and 3 respectively designate right channel and left channel signal processing sections.
  • the left channel signal processing section 3 is not shown in detail, it has the same construction as the right channel signal processing section 2, and here the right channel signal processing section 2 will be typically described.
  • Numeral 4 designates a pre-amplifier for amplifying the stereophonic composite signal detected by the pick-up 1, numeral 5 a low-pass filter for detecting only the main channel signal from the amplified stereophonic composite signal output of the pre-amplifier 4, numeral 6 a phase regulator for regulating the phase of the main channel signal detected by the low-pass filter 5, numeral 7 a separation regulator for regulating the separation by controlling the level of the phase controlled main channel signal output of the phase regulator 6, numeral 8 a matrix circuit, numeral 9 a sub-channel signal amplifier for selectively amplifying the subchannel signal contained in the amplified stereophonic composite signal output of the pre-amplifier 4, numeral 10 an amplitude limiter, numeral 11 a detector, numeral 12 a muting circuit, numeral 13 an FM/PM equalizer, numeral 14 a d-c amplifier for detecting the sub-carrier wave from the amplitude limited subchannel signal and producing a d-c output in proportion to the detected sub-carrier wave, nume
  • FIG. 2 shows the detailed circuit construction of the muting circuit 12, switching circuit 15 and fourchannel stereo indicator 17.
  • the muting circuit 12 consists of a field-effect transistor TR with the source and drain thereof respectively connected to the output terminal of the detector 11 and the input terminal of the equalizer 13.
  • the gate of the transistor TR is connected through a diode D and a capacitor C to ground.
  • the switching circuit 15 consists of a transistor TR with its base connected through a resistor R to the output terminal of the d-c amplifier 14, its emitter connected directly to ground, and its collector connected through a resistor R to the juncture between the resistor R and diode D.
  • the four-channel stereo indicator 17 comprises a transistor TR which has its base connected to the output terminal of the switching circuit 16 and its emitter connected through a select switch SW to a power supply +B, and an indicator lamp PL connected through a resistor R to the collector of the transistor TR
  • the juncture between the resistor R and indicator lamp FL is connected through a resistor R to the juncture between the diode D and capacitor C.
  • Resistors R and R serve as biasing resistors for the field-effect transistor TR
  • a resistor R serves as a collector resistor for the transistor TR and a resistor R is provided between the juncture between resistor R and diode D and ground.
  • the stereophonic composite signal output produced from the pick-up l and coupled to each channel signal processing section is amplified through the pre-amplifier 4, whose output is coupled to the lowpass filter 5 and sub-channel signal amplifier 9 respectively separating the main channel signal and subchannel signal.
  • the separated sub-channel signal goes to the amplitude limiter 10 for amplitude limitation and then to the detector 1 1 for detection before being coupled to the muting circuit 12.
  • the d-c amplifier l4 and switching circuit 16 provide predetermined outputs, so that the transistor TR is off and the transistor TR is on.
  • the power supply voltage +B is supplied, provided the pole of the select switch SW is thrown to the side of the fourchannel terminal a, through the resistor R to the indicator lamp PL, so that the indicator lamp FL is on.
  • the capacitor C is charged due to the voltage drop across the indicator lamp PL.
  • the transistor TR since the transistor TR is off, its collector is at a sufficiently large positive potential, which is coupled to the gate of the field-effect transistor TR
  • the transistor TR which constitutes the muting circuit 12 is on, and the detected signal from the detector 11 is transmitted through the muting circuit 12 and FM/PM equalizer 13 to the matrix circuit 8.
  • the signal passed through the equalizer 13 is combined with the main channel signal separated through the low-pass filter 5 and coupled through the phase regulator 6 and separation regulator 7, whereby predetermined front and back signals can be taken from the output terminals 18 and 19.
  • the output of the do amplifier 14 is momentarily extremely reduced, so that the transistor TR: is triggered, with its collector potential suddenly reduced to ground potential.
  • the field-effect transistor TR is cut off, so that it no longer couples the output of the detector 11 to the equalizer 13. In consequence, the noise due to the cessation of the subcarrier wave will not be introduced as an output, and superior reproduction can be obtained.
  • the field-effect transistor TR When a predetermined terminal voltage is built up across the capacitor C, the field-effect transistor TR is rendered on, whereupon the output of the detector 11 is coupled to the equalizer in the manner mentioned above in connection with the normal operation.
  • the detector 11 becomes operative as soon as the subcarrier wave appears, and it suddenly produces a large d-c output from that moment.
  • the muting circuit 12 is not renderedperfectly operative until the capacitor C is charged to a predetermined extent. This means that the d-c signal coupled through the muting circuit 12 to the equalizer 13 is gradually increased from the afore-said moment.
  • the select switch SW By throwing the select switch SW to the side of the two-channel terminal b, two-channel reproduction of a four-channel record can be obtained.
  • the transistor TR With the select switch SW thrown to the side of the two-channel terminal, the transistor TR is always off irrespective of the presence or absence of the subchannel signal, so that the indicator lamp PL remains off providing a comparatively low resistance.
  • the capacitor C can not be charged enough to let the fieldeffect transistor TR be rendered on upon appearance of the predetermined output from the d-c amplifier 14. This means that in this case passage of the sub-channel signal is completely blocked, and only the main channel signal is added to the matrix circuit 8, and it is taken out in situ from the output terminals 18 and 19.
  • a capacitor adapted to begin to be charged with the appearance of the subchannel signal is used to render inoperative the muting circuit by utilizing the terminal voltage across the capacitor, so that it is possible to eliminate harsh foreign sounds at the time of start of playback of a record.
  • the stereo indicator circuit which is operated according to whether the sub-channel signal is present or not, is provided with a select switch capable of rendering the indicator inoperative irrespective of the presence or absence of the sub-channel signal.
  • a four-channel stereophonic reproducing system for reproducing a CD4 type four-channel record where a composite signal obtained from a first main channel signal constituted by a sum combination of first and second audio signals and a first sub-channel signal constituted by a frequency or phase modulation of a difference combination of said first and second audio signals on a predetermined sub-carrier is recorded in one sound groove, and also where another composite signal obtained from a second main channel signal constituted by a sum combination of third and fourth audio signals and a second sub-channel signal constituted by a frequency or phase modulation of a difference combination of said third and fourth audio signals on a predetermined sub-carrier is recorded on another sound groove, said system comprising a pickup for reproducing the stereophonic composite signals from said four-channel record, filter means for separating the first and second main channel signals and first and second sub-channel signals from the reproduced stereophonic composite signals, first and second subchannel signal processing systems including pulse counter type detector means for detecting the separated first and second sub-channel signals respectively, matrix means for combining the
  • muting circuit control means each have a parallel circuit of a resistor and a capacitor, the charging and discharging of said capacitor being utilized to on off control the associated muting circuit means.
  • the four-channel stereophonic reproducing system which further comprises stereo indicator means operated according to whether said first and second sub-channel signals are present or not, and in which said muting circuit control means each have a switching circuit on-off controlled according to whether the sub-carrier wave of each of said first and second sub-channel signals is present or not and a capacitor adapted to be charged and discharged according to the output of the associated stereo indicator means, said capacitor being adapted to be charged at the time of start of playback of said four-channel signal, the terminal voltage built up at this time across said capacitor having the effect of gradually rendering inoperative the associated muting circuit means which is controlled by the output of the associated switching circuit and said terminal voltage across said capacitor.
  • stereo indicator means each include select switch means having a twochannel terminal and a four-channel terminal, said stereo indicator means being rendered inoperative irrespective of the presence or absence of the first and second sub-channel signals by throwing said select switch means to the two-channel terminal, whereupon the charge stored in each said capacitor is adapted to be reduced to render each said muting circuit means operative irrespective of the output of each said switching circuit, thereby opening the first and second subchannel signal processing circuits.
  • said muting circuit means each comprises'a field-effect transistor having a source terminal to be used as a corresponding subchannel signal input terminal, a drain as its output terminal and a gate as control terminal connected through a resistor, a diode and a capacitor to ground
  • said switching circuits each comprise a transistor having its base connected to receive an output representing the presence or absence of the sub-channel wave of each of the first and second sub-channel signals, its collector connected through a resistor to the juncture between a resistor connected to the gate of the field-effect transistor and said diode and its emitter connected directly ground
  • said stereo indicator means each comprise a second transistor having its base connected to receive an output representing the presence or absence of the first or second sub-channel signal and its emitter connected through the select switch to a power supply when said select switch is thrown to the the fourchannel terminal, and an indicator lamp connected through a resistor to the collector of said second transistor, a juncture between said indicator lamp and resist

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Stereo-Broadcasting Methods (AREA)
  • Stereophonic System (AREA)
US471827A 1973-05-25 1974-05-20 Four-channel stereophonic reproducing system Expired - Lifetime US3911231A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP6193673U JPS5136481Y2 (enrdf_load_stackoverflow) 1973-05-25 1973-05-25
JP6193773U JPS5123285Y2 (enrdf_load_stackoverflow) 1973-05-25 1973-05-25

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US3911231A true US3911231A (en) 1975-10-07

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US471827A Expired - Lifetime US3911231A (en) 1973-05-25 1974-05-20 Four-channel stereophonic reproducing system

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US (1) US3911231A (enrdf_load_stackoverflow)
AU (1) AU481062B2 (enrdf_load_stackoverflow)
CA (1) CA1005350A (enrdf_load_stackoverflow)
DE (1) DE2425191A1 (enrdf_load_stackoverflow)
FR (1) FR2231065B1 (enrdf_load_stackoverflow)
NL (2) NL165027B (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4001518A (en) * 1974-03-12 1977-01-04 Matsushita Electric Industrial Co., Ltd. Discrete four-channel disc reproducing system

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3825697A (en) * 1973-07-27 1974-07-23 Gen Motors Corp Phase-lock-loop fm-stereo decoder including stereophonic/monophonic blend system for reducing audio distortion
US3842211A (en) * 1971-03-10 1974-10-15 Gen Electric Monolithic stereo decoder

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3843850A (en) * 1970-06-26 1974-10-22 Victor Co Ltd Four channel record reproducing apparatus with muting of speakers not used for stereo or monaural records
JPS5524320B2 (enrdf_load_stackoverflow) * 1972-05-24 1980-06-27

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3842211A (en) * 1971-03-10 1974-10-15 Gen Electric Monolithic stereo decoder
US3825697A (en) * 1973-07-27 1974-07-23 Gen Motors Corp Phase-lock-loop fm-stereo decoder including stereophonic/monophonic blend system for reducing audio distortion

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4001518A (en) * 1974-03-12 1977-01-04 Matsushita Electric Industrial Co., Ltd. Discrete four-channel disc reproducing system

Also Published As

Publication number Publication date
AU481062B2 (en) 1977-02-17
NL165027C (nl)
DE2425191A1 (de) 1974-12-19
NL165027B (nl) 1980-09-15
FR2231065A1 (enrdf_load_stackoverflow) 1974-12-20
CA1005350A (en) 1977-02-15
AU6923474A (en) 1975-11-27
FR2231065B1 (enrdf_load_stackoverflow) 1978-06-16
NL7406743A (enrdf_load_stackoverflow) 1974-11-27

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