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■ Reproduction method of at least four individual audio information signals ■ Japanese Patent
Application No. 46-30898 [phase] Application No. 46 (1971) May 11 Priority claim 61 June June
70 [phase] United States o44196 open closing 47 -20 @ 47 47 (1972) January 5 0 Inventor Ben
Jami / · B Bower United States Statford Red Fox Road 92 Conn. Daniel W. Gravero [Fa] Attorney
Attorney Sugimura Toshio 1 invention Detailed description of the invention The present
invention accommodates at least four individual audio information signals in two information
channels, the signals in each of which being at least three of the said audio information signals
combined At least one of the at least three audio information signals is When there are two or
more channels, for example, two independent recording tracks accommodated in the two
information channels so as to have a relative phase difference other than the in-phase or the antiphase between the two channels. When reproducing the at least four individual audio
information signals from a recording medium such as a stereo disc record or a magnetic tape, the
information signals are supplied to at least four speakers so that sound may appear from the four
individual sound sources. The present invention relates to a method of reproducing at least four
individual audio information signals, which provides the listener with Because it is possible to
obtain a wide variety of sounds and musical tones by the well-known phenomenon that the
quality of the playback sound can be improved by increasing the number of channels in the
multi-channel recording and playback & 111 Recently, more and more attention has been
directed to multichannel recording and playback. In the early records, only the number 'single
channel, ie monaural record, was used, and from 40 to 50 years ago, the value of recording and
playing back two separate information channels has been recognized and is now Stereo
recording. Known as Regeneration. However, using two information channels is not enough to
get a full sense of presence. For example, when the listener is located in front of the orchestra,
the listener listens to the sounds coming from different directions and different instruments, as
well as the reflections from the walls and ceilings, which causes the listener to You will feel as if
the sound comes from space (hearing). However, when playing back with only two channels, it is
difficult, if not impossible, to create a real sense of realism for such spatial perception.
Previous experiments have shown that at least three independent channels are required to create
a satisfying presence when playing orchestral music. According to the latest stereo disc records,
recording or encoding or modulation is performed along two separate channels which are
geometrically at 90 ° to one another and at 45 ° to the surface of the record disc. Usually, a
third central channel is provided, which is mixed as a phantom channel in the other two channels
(matrixing) and recorded as lateral modulation parallel to the record surface. Also, in order to
obtain special effects, it is often practiced to provide several channels in opposite phase to the
track. As such a record, there is a test record model 5TR110, 111, and 112 manufactured by, for
example, CBS Laboratories in the United States. During playback, the third or central channel
appears on the two speakers of the stereo playback device with equal magnitude and equal
phase, and the listener located in the middle of these two speakers has the sound of the third
channel, which is It feels like it is located between the other two sounds. When the fourth vertical
channel is reproduced by a normal two-speaker stereo reproduction device, the sound source is
not localized and gives a feeling of expanded sound (5pread5ound). Attempts have been made to
reproduce the sound of the third center channel with a separate speaker, but the result is not
fully satisfactory, so although many stereo records have a center channel, but mostly The stereo
reproduction device of the present invention uses only two speakers. In Japanese Patent
Application No. 46-30897 according to the applicant of the present invention, the two-channel
record reproducing apparatus is provided with third and fourth reproduction channels, and the
third and fourth speakers are provided with sums and differences of left and right channel
signals. It is described that each signal is supplied. The left and right speakers are placed, for
example, on the left and right sides of the listening room, and the speakers for two vertical
channels are placed on the front and back of the listening room. Each speaker reproduces a
signal of the power of H of the information of each channel and the signal of the adjacent
channel supplied to the channel corresponding to that speaker. According to such a reproducing
apparatus, although a quasi-four channel effect can be obtained, it is not possible to obtain a
perfect auditory sense in which the sound of each channel is reproduced independently of each
other from the corresponding speaker.
When the record disc recorded as described above is reproduced by the monaural record
reproducing apparatus, the channel recorded in the vertical direction is not reproduced.
Naturally, like this! It is desirable that the 4 channel 11 records be compatible with conventional
monaural and stereo records. That is because these monaural and stereo records are now used in
great numbers. In other words, when regenerating a new recording medium with a mono or
stereo playback device, it is desirable to be able to listen to the conventional recording playback
device's speaker device for all channels recorded on a multichannel disc. It is also an object of the
present invention to provide a stereo disc record, a two track tape device having recording and
reproduction heads individually provided for each of the two tracks, or a stereo multiplex for
transmitting two independent information channels or information tracks. A speaker that
properly encodes four-channel audio information and records or transmits it on a two-track
recording medium such as broadcasting, and further decodes the encoded information
appropriately 11111111EndPage: 2 and is provided independently In order to provide at least
four channels of stereo reproduction method, the listener is made to feel that sounds are heard
from the four individual sound sources by adding them individually. Another object of the
present invention is to provide a method of stereo reproduction of at least 4 channels intended to
make the hearing of at least 4 individual channels appear more realistic. The present invention is
applicable to the above-mentioned various 2-track recording and / or transmission devices
currently used, and supplies two of the four independent information channels to the 2-track in
the usual way, The other two channels supply their respective equal parts in phase and in phase
with each other relative to the two tracks. When the present invention is applied to a 45-45 °
stereo disc record, two channels are recorded on two separate tracks provided on the sound
groove wall of the record, and the 11th and 11th left of the stereo cutters for the third channel.
Record by supplying in-phase equal-magnitude signals to the 11 right 'channel and modulating
by grooved lateral modulation and also for the 4th channel on the 11 left 11 and 1' right 1
terminals of the stereo cutter. Recording is carried out by applying longitudinal modulation of the
sound groove by supplying out-of-phase but equal-sized signals.
The fourth signal is also divided into equal sized signals 180 ° out of phase so that longitudinal
modulation has a horizontal component so that this horizontal component can be detected by a
conventional monaural or stereo record player. The fourth signal is passed through the phase
shift network to generate two signals that are out of phase with each other, without the recorder
needle being moved only up and down by the difference signal. Make it do an elliptical motion.
The information recorded or transmitted to the medium is reproduced by means of a suitable
converter to extract the two combined signals, namely the '' left 'signal and the' right 'signal. The
11 left +1 signal has a portion of the third channel and a portion of the fourth channel in
addition to the left channel signal, and the 'right' signal is a portion of the right channel signal, a
portion of the third channel signal and a portion of the fourth channel However, it has a negative
component. Four independent signals are taken out by appropriately adding and subtracting
such combined signals. In each of these four independent signals, the original four channels are
the main components respectively, but a part of the other two channels is also slightly
accommodated. By automatically controlling the instantaneous amplitudes of the four individual
signals supplied to the four east corresponding speakers in the reproduction according to the
invention in response to the signals present on the four channels at that moment, It can give
almost complete hearing of two separate independent sound sources. The invention will now be
described with reference to the drawings. As noted above, the invention is applicable to any of
the known two track schemes, but the invention will now be described with the example of a 4545 ° stereo disc record. First, the present method of recording stereo audio signals including the
third channel, ie, the center channel, and the method of reproducing these audio signals with a
two-speaker stereo reproduction apparatus will be described with reference to FIGS. In FIG. 1, the
left channel signal R and the right channel signal R and the center signal C are applied to the two
terminals of the stereo cutter 10, which are formed as known. The cutter 10 has a recording
needle (cutter needle) 12 and is used to form a groove in the lacquer of the master disc 14 which
rotates on a recording turntable (not shown). The central signal C is passed through a matrix of
known configuration, i.e. the signal divider 16 and the signal components obtained equal to 0,
707 C are added to each of the L and R leads. As is well known in the flute technology, the point
of cutter 12 moves in a plane substantially perpendicular to the disk surface, as shown in the
vector diagram of FIG.
When the left channel signal is supplied, the nine hands move along an arrow that makes an
angle of 45 ° with the horizontal direction, and when the right channel signal R is supplied, & &
the pointer with respect to the horizontal direction- Move along the 45 ° angled arrow RK.
When the component 0.707C of the C signal is added to each of the L and R conductors, the
needle moves with three arrows CIKU. The size of this arrow C is 0.707 ct + π), which is equal to
the size of either the thick arrow or R, but its direction is horizontal. Instead of supplying the R
and C signals directly to the cutter as shown in FIG. 1, it is also possible to first record on a two
track master tape recorder and drive the record cutter by means of the tape playback output, as
is known. The difference signals shown in FIGS. 1 and 11111111 EndPage: 32 will be described
later. An example of groove modulation formed by the above means is shown in FIG. The tL
groove is modulated according to the arrow when only the left channel signal is supplied. This
modulation number is limited to only one wall of the groove. Similarly, when only the right
channel signal R is provided, it is modulated in the direction of arrow R on the opposite wall of
the stutter channel. This arrow R is perpendicular to the arrow as shown. When equal amounts of
central signal C are supplied to the L and R leads, both walls of the sound groove are
simultaneously and equally modulated in the direction indicated by arrows L = 0.707 C and R =
0.707 C as shown by arrow C. Move horizontally FIG. 4 shows an outline of a reproducing
apparatus of stereo records recorded in this manner and including R and C signals. This
reproduction apparatus comprises a stereo pickup having a cartridge 18 and an i reproduction
needle 20, and the reproduction needle 20 of noon is inserted into the sound groove of the
record and driven by groove modulation to take out the output voltage from the L and R
terminals. When only modulation of the L signal exists in the sound groove, the & ζ output
signal appears only at the L terminal, and this output signal is amplified by the appropriate
power amplifier 22 and reproduced by the speaker 24. Similarly, when only the modulation of
the R signal is present in the sound groove, the output signal appears only at the R terminal of
the pickup, and this output signal is amplified by the power amplifier 26 and supplied to the
speaker 28. When the sound groove is engraved by lateral modulation (lateral modulation) in
which both left and right signals are equal, equal signals, ie, 0.707C appear in both left and right
speakers, and the speakers 24 and 28 A virtual sound source (phantom source) C as indicated by
a broken line circle in the figure is determined in the middle.
However, such a sense of hearing is sensed only when the listener 30 is located at the center, and
unless the listener has taken special measures to adjust the directivity of the speaker with respect
to the position of the listener, the listener will be on either side. When offset, the C signal will be
heard by the closest speaker. The three channel records mentioned above are compatible, but the
reason is that all of the R and C signals have horizontal components, so when playing on a
monaural record player that only feels in the lateral direction, these random signals can be heard
The strength of these reproduction signals is out of balance with the sound shown by the director
W4444441 at the time of recording. Even when the third channel is introduced, only two
independent information channels are actually reproduced in the above-mentioned system. The
third channel C is included in both the left and right channels, so the listener can hear the C
signal reproduced from the speaker closest to him normally. This central channel can also be
played on a separate speaker device as shown by the dotted line in FIG. An amplifier for that
purpose is commercially available. According to this, the listener can sense central information
without making his position equal distance from the left and right speakers. Referring again to
FIGS. 1 to 3, the fourth channel D is divided into equal signal components by the matrix or signal
divider 32, and these divided signal components are added to both the left and right channels in
reverse phase with each other. The fourth channel D can be introduced into a two channel stereo
device. As shown in FIG. 2, by thus supplying the D signal, the needle: is 0.707 times the amount
obtained by mutually subtracting the components contained in the left and right channels, ie 0
Move vertically along arrow & C by the size of .707 (LR). As can be seen from FIG. 3, due to this,
the phases of the left and right movement of the needle are shifted from each other to produce
the up and down movement. In the device shown in FIG. 4, the vertical modulation is reproduced,
and the cones of the two speakers are driven in opposite directions to each other to add out-ofphase sound pressure to the listener's ear. When the sound pressure is applied, the listener can
not localize the sound because it does not correspond to the normal listening state. Difference
signal 1] L As shown by D in the dotted circle, it appears at an indeterminate position in space,
and the listener can not localize the difference signal. Furthermore, among those who listen to
such out-of-phase sounds, there are those who are dissatisfied with feeling that strange sound
pressure is heard.
However, this dissatisfaction is somewhat solved by the device described in Japanese Patent
Application No. 46-30897 according to the proposal of the present applicant. In such a device
the difference signal as well as the central signal is also reproduced on a separate speaker. In
order to be able to obtain better compatibility with monaural and conventional stereo record
players and to improve the sense of reality when playing with four separate channels with it, we
use Bauer It is preferable to add a difference signal as suggested in the paper [Technologies for
better stereo realization] (IEEE TRANSACTION S 0 N AUDIO S Vol AU 11 y Na 3 # May-Junet
1963). At the same time, instead of adding the difference signals to the left and right inner
channels in equal magnitude and in antiphase with each other as in the circuit of FIG. 1, in the
present invention, the difference signal as shown in FIG. Through an audio phase shifting
network 32 to split the incoming signal into two equal amplitude signals D1 and D2. Each of
these signals D □ and D2 includes all frequency components of the difference signal but is out of
phase with each other. It is preferable that the relative phase shift be in the range of 110 ° to
170 °. In particular, an angle of 135 ° was optimum. When the two signals D □ and D2 are
thus out of phase with one another, the point of the needle performs an elliptical movement as
shown in FIG. 6 rather than just moving up and down as shown in FIG. Is easily understood. The
range of motion of the needle is as shown by the dotted line in FIG. 6, and the direction of the
elliptical motion depends on whether the signal DI leads or lags D2. It is important to note that
the groove has a horizontal component determined by the horizontal width of the ellipse, so that
all four signals can be reproduced by either the monaural record player or the stereo record
player. is there. That is, a record having four separate channels is completely compatible with
conventional playback devices. However, in the monaural record reproducing apparatus, the
signal is attenuated by about 8 db. Although the above mainly describes the case where
information of four separated channels is recorded on a two-track stereo recording board, using
a similar technique, for example, recording similar signals on a two-track tape, or It is of course
possible to send similar signals from the stereo multiplex broadcast facility of
In the following, the invention will be described in the context of a reproduction device in which
a four-channel signal is suitably reproduced so that four channels can be supplied separately and
independently to four different speakers. The reproduction method according to the invention is
applicable to any of the known two-track reproduction systems, except for the converter means
required to extract the signal from the recording medium. The case where the reproduction
method of the present invention is applied to the record disk recorded as described above will be
described with reference to FIG. The signal being recorded is taken out by a stereo pickup of the
type shown in FIG. 4 and supplied directly to the reproduction apparatus shown in FIG. 7 or via
two suitable amplifiers 40 and 42. As is apparent from the foregoing, the 11 left II signal
indicated by LT is a combined signal LT = L + −0.707C × D1 obtained by adding the 0.707C
signal and the D1 signal to the L signal. Similarly, the "right" 1 'signal RT is a composite signal RT
= R + 0.707 C + D2 with R, 0.7070 and D2 signals. Providing the outputs of amplifiers 40 and 42
respectively to the two speakers, the reproduction in that case is equivalent to that of a
conventional two-channel stereo reproduction system. However, in the reproduction apparatus
according to the present invention, four signals are also supplied to two signal dividers 44 and
46 with known configurations of LT and RT doubled signals, and appropriately adding and
subtracting components of these combined signals. L /, c /. Generate D 'and R'. These signals L'tC
', D' and R 'are 4 channels L respectively. It comprises C, D and R as main components, and
further has each other two channels, though only a few. Thus, the signal series L, C supplied to
the individual speakers L, C, R and D after being amplified by the appropriate power amplifiers
48, 50, 52 and 54 respectively. Rather than being composed of only single information
corresponding to each of the R and D channels, they are diluted by the inclusion of information
portions from adjacent channels. In the present invention, by controlling the instantaneous
amplitude of the signal supplied to the four speakers by means of the logic circuit shown by the
dotted block 56, the listener is given almost complete hearing of four separate independent
sound sources. Let it go. For this purpose, the present invention takes advantage of the nature of
music that is normally reproduced from records, and utilizes a phenomenon known in acoustics
as the "precede-nce effect". In most music & L individual players do not play continuously, but
rather increase sound, decay sound, beating!
Sound etc. produce a constant change pattern that does not occur simultaneously but mixes with
one another. For example, first the sound of a drum appears on channel L, then the sound of
cymbal appears on channel R, and the voice of a soloist who speaks various syllables appears on
channel C, and so on. With the speaker device switched appropriately, each time you start on a
channel with a specific [1111111 EndPage: 5 shock sounds, turn on the speaker for that channel
or selectively amplify the signal and respond accordingly to the remaining speakers If it can be
turned off or attenuated, the listener's attention is directed only to the specific sound that is
coming out of that speaker, and even if the sound changes to another speaker, that listener will
continue to be the first speaker. I have the illusion that you can hear the sound from This is
known as 1 Precidence effect, that is, to the listener even after the particular speaker ceases to be
a true sound source when a certain sound is generated by a given speaker and then gradually
switched to another speaker. Is caused by the phenomenon that the sound continues to be heard
from that particular speaker. Thus, the function to be performed by the control logic 56 of the
playback device identifies which channel's signal is strongest at any instant and either turns that
channel on or selectively increases its gain, At the same time, the remaining channels are
attenuated or turned off. As the sound of the first identified channel diminishes and other sounds
appear in another channel, the logic rapidly reduces the gain of the first channel and increases
the gain of the other channel . When considering the operation of such logic, it is effective to use
the following truth table. When an audio signal is present in the logic unit, the logic unit exhibits
the following logic. If L signal-0, only R signal is present. If the R signal is -0, only the L signal is
present. If it is C signal 〇, only D signal exists. If D signal-0, only C signal is present. This is a
form of negative logic, and according to the truth table, for example, no sound is present in
channel L or the sound of channel L is reduced to turn on R channel or increase its gain. Etc.
Referring again to the logic device, when providing amplifiers 40 and 42, the outputs of these
amplifiers are provided to gain control amplifiers 58 and 60, respectively, and the gains of these
amplifiers are indicated by gain control lead 62 between these amplifiers To match and control.
The LT and RT signals are applied to the amplifiers 58 and 60 rl 111 111 via the signal change
networks 59 and 61 respectively. These two networks 59 and 61 are identical and exhibit
transfer characteristics similar to the contours of the loudness characteristics of the human ear
over the required audio frequency range at moderate loudness levels. In the article "Loudness
3 spp-141 151 ° 1966)" by Bauer and Emil Torick, a set of equal loudness profiles is shown and
described. ing. The loudness contours equal to the 70 horns developed in the study described in
this paper are shown in the form of inverted sensitivity curves in blocks 59 and 61. Here, the
transfer characteristic has a peak of about 8 db in the high frequency part (about 4 KHz), is
approximately constant from about 2 KHz to about 50 Hz, and shows a drop of about 5 db at
about 50 Hz. Networks 59 and 61 are intended to properly shape the signals supplied by the
converter to gain control amplifiers 5B and 60, so that the signal switching logic as described
herein will be individual t, /, C. /, D / and R 'signals are provided to each channel based on their
associated loudness rather than their energy fatness. For example, due to the weight curves of
networks 59 and 61, a low frequency but high energy signal generated from the tram, for
example from a piccolo, may cause a high frequency (a low energy signal to be switched
incorrectly. I will try to avoid it. The transmission characteristics of circuits 59 and 61 may be
implemented in various ways, a preferred example of which is shown in FIG. 7A. Here, the circuit
59 includes an air resistance R1, a resistance R2 having a lower value than that, a capacitor C1
and an inductor L1, and a series branch connected in parallel with the resistance R1, and
between the inductor L1 and the ground. It has a small resistor R3 connected and a series
resistor R4 connected between the inductor L1 and the amplifier 58 (or 60). The center of the
transfer characteristic peak is generated at about 4 KHz by appropriately setting the values of
the respective elements of the series branch and cooperating with the parallel resistor R1. If an
example of the value of the element used by the circuit of FIG. 7A is shown, R1 = 5. IK Ω
[1111111 EndPage: 6R2 =] :, 6 to 6 ΩR3 = 91 ΩR4 = 1.
OK Ω C1 = 0.01 μf L1 = 300 mh. In order to obtain better results with a particular decoder, the
shape of the transfer characteristic may be changed to an accurate one by means of a flooding
experiment. Alternatively, it may be desirable to provide a specific type of music controls. In the
control circuit, the outputs of amplifiers 58 and 60 are divided into four separate outputs by
isolation circuits 64 and 66 in the same manner as circuits L44 and L46 take out outputs L ', C',
D 'and R'. . Separate into C ", D" and R ". The two output sets consisting of these four outputs are
the same as each other in the output set L ", C", D "and R" of the 75 originals whose music
contents are similar to each other, and the dynamic range of the record is by the circuits 59 and
61. Changes and changes are kept constant by the first gain amplifier 58 and 600 action. Thus,
in order to keep the output level constant, the L ", C", D "and R" signals are rectified by the
rectifiers 6B, 70, 72 and 74 respectively, and the separation resistors 76.78.80 and 82 are
further used. Addition is performed to take out the sum signal from between the common
resistors 84. The voltage appearing across common resistor 84 is provided via lead 86 to gain
control lead 62 of amplifiers 58 and 60. These amplifiers 58 and 60 respond to the above
voltage to keep the average voltage between the common resistors 84 substantially constant. In
order to enhance the gain control function, four capacitors 88.510.92 and 94 are connected
between the resistors 16 ° 78.80 and 82, respectively, whereby the voltage rectified is more of
the waveform [111111] than its instantaneous value. The sum of the voltages between the
resistances 76.78.80 and 82 is kept constant. The reason is that the voltage appearing across the
relatively small resistor 84 is the sum of the four rectified voltages. The operation of such a gain
control circuit will be described by means of several examples. Let us consider the case of
reproducing a record having only a single signal, for example, the left signal. Here, the amplitude
of the left signal is assumed to be 1. According to the vector diagram of FIG. 2, the relative values
of the voltages eltecsed and er appearing between the resistors 76.78.80 and 82 respectively
become 1, 0.707, 0.707 and O respectively. The sum of these voltages is 2.414, and the gain
control amplifiers 58 and 60 keep the voltage across the resistor 84 at this value regardless of
the audio signal level of channel L. The above is an example of the circuit operation, and the
details will be described later. Here, assuming that only the C signal is present, in this case, the
voltages e, g, ected and er are respectively 0.707, 1, 0 and 0.707.
The sum of these voltages is also 2,414. When an incoherent signal, for example a signal similar
to white noise, ie signals originating from two different sources, is simultaneously applied to
channels L and C, the voltage corresponding to the sum of these two channels is the square of
the two-sided pressure Equal to the square root of the sum of Therefore, the unadjusted sum of
signal and C is e, /=1.223, ec = 1.223, ed = 0.707 and er-0, 707, as shown in the following Table
II. The sum of these four voltages is 3.860 so that the automatic gain control amplifier adjusts
the component voltages instantaneously to a total of 2.414. That is, by reducing each of these
voltages in proportion to the fraction 2.414 / 3.860, the adjusted value of el = 0.760. ec = 0.760.
This gives ed = 0.440 and er = 0.440. [111111] eccederEndPage: 7 Let us consider the case
where a third channel, for example R, is present. The voltages corresponding only to this channel
are e, g = 0 * ec = 0-707 ted = 0.707 and er = 1. Again assuming that all three signals are
incoherent signals such as white noise, the unadjusted values of e ', g, ecsed and er obtained for
(L + C + R) states are individual for each of these three channels It is obtained by taking the
square root of the sum of the squares of the voltages, resulting in 1.223.414.1.223 and 1.223,
respectively, as shown in Table I. Adding these four voltages together gives a total of 5.083,
which causes the automatic gain control amplifier to immediately reduce these component
voltages by the fraction 2.41415.083 to produce the regulated voltage shown in Table 1 . Here,
when the fourth voltage corresponding to the D channel is added, the value of each of the
voltages obtained by adding the four components is 1.414, and when the automatic gain control
amplifier reduces the overall value to 2.414. The value of each component voltage is 0.6. Now,
returning to the right-hand part of FIG. 7, four signals t /, C /, D / and R 'are supplied to the
respective gain control amplifiers 96. 98, 100 and 102 and, if necessary, further amplifiers 48.
50, 52 and 54 and then applied to each of the four speakers L, C, D and R. A gain control
amplifier is an important element of the present invention and, in accordance with the logic
described above, these amplifiers control the gain of the signals applied to the individual
When the above-mentioned signal is incoherent but exhibits a constant frequency characteristic,
the peak value added by the logic unit is not equal to the effective value but approximately equal
to the sum of the signals. However, this does not deviate from the above analysis. By adding the
component voltages elsecsed and er to the gain control amplifier, the necessary control is
performed as follows. That is, el is fed to amplifier 102 to control the R 'signal, er is fed to
amplifier 96 to control the L' signal is fed to control-1 ec to amplifier 100 to control the D 'signal,
and ed is then amplified The signal is supplied to the group 98 to perform C 'double signal
control. In order to implement the above truth table, various combinations of rectifier 68, 70. 72j,
shimmer F1 j + s-jm 2 曽 jamMl-、, nores rb 7 1 1 ≠-[111 111] are negative voltages. In
addition, gain control amplifiers 96, 98, 100 and 1020 control circuits are positively biased by
each of cells 104, 106, 108 and 110 by a relative voltage of 0.6 volts. The gain control amplifier
has a control characteristic as shown in FIG. 8. This characteristic is such that when a voltage of
0.6 volt is applied to the gain control terminal of the amplifier, its gain is maximized and takes
the value l. When the applied voltage decreases to zero, the gain of the amplifier decreases to
0.707 times the maximum value. That is, the gain is reduced by 3 db. The control characteristics
drop sharply below 0 volts applied voltage, gain is 0 when the gain control voltage is -0,067
volts, and the amplifier is turned off. Next, the logic circuit 56 for the four states of only L
signals, two signals such as (L + C), three signals such as (L + C + R), and four random incoherent
signals (L + C + R + D) I will describe the operation of As can be seen from Table I, kler = 0 "when
only L signal is present, so a bias of +0.6 volts completely turns on the amplifier 96 which
controls the L 'signal, while the other magnitude is not Is -i, o + 0.6--0.4. The negative voltages of
-0, 707 + 0.6 = -0, 107 and -0, 107 are supplied to the amplifiers for R /, D / and C 'times signal
control respectively. As a result, amplifiers 100 and 98 are biased below cut-off and
gain is zero, so the L signal, which would otherwise appear on speakers C and D, appears only on
speaker L. Similarly, when any one signal appears in only one channel, that signal turns on only
the gain control amplifier for that signal.
Now, referring to the case where both L and R signals are present, as can be seen from Table I
and FIG. 8, the voltage -0,76 volts supplied to amplifiers 100 and 102 exceeds the bias of +0.6
volts. , Turn off speakers D and R, but turn on with a gain of just one less than these amplifiers
96 and 9B & Q1 by the voltage -0,440 volts supplied to amplifiers 96-and 98. Similarly to L
signal and C signal from L and C, EndPage: 8 when ILL 7 lig & signal is simultaneously present,
ec is sufficiently negative, as can be seen from the workmanship and FIG. The amplifier 100
controlling the signal supplied to the power supply is turned off, while the voltages supplied to
the other three gain control amplifiers are -0, 557. These amplifiers are the belt is maintained in
the ON state, their gain is reduced by about 2.5 dB. In this way, the amplifiers 96/98 and 102 are
turned on to make L /. The C 'and R' signals are reproduced from each individual speaker. Finally,
if all of the L, C, R and D signals are of equal magnitude to one another, then each of the gain
control voltages e, /, eojed and er are all at 0.6 volts and the four amplifiers 96. All 98, 100 and
102 are on and each signal is applied to the respective speaker. However, as can be seen from
the control characteristics, the gain of the amplifier drops by about 3 db when all four signals are
present. In this way, the total audio energy reproduced by the loudspeakers remains almost
constant regardless of the number of signals present. As is apparent from the above, in the
present invention, the important object of the present invention is achieved by operating the
logic device so that the speaker corresponding to the main sound present at each moment in the
logic device is turned on. Can be achieved. In fact & all the signals rarely occur at the same time,
but rather there is always an interplay of various instruments, thereby properly turning the
speakers on and off, completely from the four separate sound sources Makes natural hearing be
played by four speakers. For best performance, determine the time constant of rectifier circuit
6B-74 to have a very fast start-up time on the order of 0.1 ms and a relatively slow decay time on
the order of 10 ms. Is preferred [111111]. Similarly, it has been confirmed that it is preferable to
make the operation start time of the gain control amplifier 96-102 extremely rapid, on the order
of 0.1 millisecond, and to make the attenuation time on the order of 0.4 second.
However, these start times and decay times can be widely adjusted without significantly
impairing the operation of the circuit. In principle, the regeneration device of FIG. 7 is sufficient,
but in this case the control characteristic of & cylinder 8 has a narrow range of discrimination
between the off state and the on state. There is a disadvantage that the voltage appearing
between 76 and 82 must be controlled in close proximity. An example using a differential
discriminator circuit to improve this point is shown in FIG. The right hand portion of the circuit
of FIG. 9 is identical to the corresponding portion of FIG. 7 and like parts will be designated with
the same reference numerals. In the logic circuit 59 ', the polarities of the rectifiers 6B, 70, 72
and T4 are inverted as in FIG. 7 so that the voltages generated between the resistors
80.82 and 84 become positive. Furthermore, these voltages are added to the adders 112, 114 °
116 and 118 and differentially added, without directly supplying them to the gain control
amplifier. In these adders, the main voltage is weighted by three times in the negative direction,
and the remaining three types of voltages are added by one time in the positive direction. For
example, the adder 112 is supplied with the main e and signal appearing between the resistors
82, multiplied by -3 and added with the voltages eZ) ec and ed respectively added by the
weighting factor 1. The main voltages supplied to the adders 114 ° 116. 118 are ed and ect j /
respectively. Thus, the output voltages e7jec'jed 'and er' are extracted from the adder, and the
values of these output voltages are as shown in Table 1 for various combinations of the abovementioned signals. The value & weight value shown in Table 1 is derived by applying the abovementioned weight coefficient to the relative power value shown in Table I. ec 'ed' e, '0.414-0.4141.586 0.640-0.640-0.640 0.414 [111111] EndPage: 9 As can be seen from Table 3, differential
addition Can significantly increase the discrimination range, and the gain control circuit shown in
FIG. 10 can be used. In this case, the gain of the amplifier is l when the value of the control
voltage is +2.4 volts, and the gain is 0.707 (3 db down) when the control voltage is 0 volt. The
characteristic curve drops sharply when the control voltage goes below 0 volts and the amplifier
is cut off when the control voltage is -0,414 volts. As analyzed for the gain control characteristics
of FIG. 8, and considering also in the case of FIG. 10, the right amplifier is turned on in response
to the main sound present in the device at any time. I understand that.
As far as the gain control circuit number cutoff of FIG. 10 is concerned, there is much more
margin than the gain wedge curve of FIG. 8 and the reproducing apparatus of FIG. 9 is much
more stable than that of FIG. Furthermore, the voltage et! ! , Ec ', ed' and er 'are differential
voltages, so even if the gain control characteristics of the amplifiers 58 and 60 deviate slightly
from the perfect ones, the operation of the device is much more than in the circuit of FIG. It has
no effect. Each of the control signals extracted from the adders 112-118 is supplied to the gain
control circuits of the respective gain control amplifiers 96-102 through appropriate waveform
shaping circuits. The circuit for achieving the gain control characteristic of FIG. 10 can be
obtained in various ways. Here, an example of a circuit that has actually worked well will be
described. This circuit comprises, for example, a limiter 120 with limiter levels -0, 4 volts and
+0.4 volts, to which is connected a time constant circuit 122 and a waveform shaper 124 of the
illustrated transfer characteristic. By combining these circuits, amplification control
characteristics as shown in FIG. 10 are obtained to control the gain of the amplifiers 96-102. The
operation start time of the circuit is as quick as about 0.1 millisecond, and the decay time is as
slow as about 0.4 second. However, these can be set to various values such as JJ-& lIgl, s-, j + rm
+ a ++, and so on. It works independently as "11"-IA + L 1--es & MM & ++, +-+-----Fyx 佑 01iS
71/7 "1 rFilFJi'lly-> sl, i J /% / n 烹) x m + w-ball-p . In other words, any one of the speakers is a
momentary noise, and the remaining speakers are off or have a reduced gain. These two
channels can be switched together in response to the relatively simple 1111111 signal shown in
FIG. Even in the remaining two channels, these two channels can be switched simultaneously in
response to the presence of the main signal in any of them. For example, the gain control
amplifier 96 and IQ2FL individually control the gain of the signal supplied to the L and R
speakers and supply the same control signal, and the amplifiers 98 and 100 controlling the
speakers C and D are identical to the same signal. Control. The L and R speakers can be placed on
opposite corners of the listening room and the C and D speakers can be placed on the other
opposite corners.
In that case, it is necessary to raise and lower the speakers at these opposite corners. The control
signals are derived analogously to the circuits of FIGS. 7 and 9, the details of which will not be
described again here. However, it is only necessary to provide one adder 130 and a phase
inverter 132 to obtain a signal to supply to the gain control amplifier 96-102 in this example.
The ez and er voltages extracted from the rectifier are supplied to the adder 130 with a
weighting factor of -1, and the ec and ed voltages are supplied with a weighting factor of 11.
When only one of the R and L channels is present, it is taken out of the transadder 130 and a
control signal modified by an appropriate time constant circuit 134 is supplied to the amplifiers
96 and 102 to both the L and R speakers. Turn on. However, since only one of these L and R
channels is on, the sound appears only from the corresponding speaker. Similarly, when both L
and R channels are present at the same time and there are no signals on C and D channels, the L
and R speakers will be turned on again, and the respective signals will be reproduced from the
respective speakers. As in the case of simulating two independent channels, any one of channels
C and D 'JIJ-'rrNLj'o) vg vgva, す z z om 帥 1 backward KG knee ++' / IV 16 + − + 11−t + V′a /
l + 4-16% /! 1; invert this control signal to have the proper polarity, and at the same time, do not
invert the amplifiers 96 and 102? 1 1 ′ ′ F # 11 −♂ These amplifiers are turned off EndPage:
10, when both C and D channels are present, the C and D speakers are turned on and the other
speakers are turned off. Since the speakers C and D play back only the signal of the
corresponding channel, two additional channels can be simulated well. If signals are
simultaneously present in any two adjacent channels, the control signal will be zero, and in this
case the phase inversion will have no effect, so all four amplifiers will be on. However, the gain in
that case is reduced, that is, 3 db down. As apparent from the above, according to the present
invention, it is possible to reproduce 4-channel information recorded in a 2-track apparatus as 2combined signals by 4-independent speakers. Moreover, according to the reproduction method
of the present invention, in response to the transient of the music sound, it is detected which
channel is the main signal and switching to that channel while at the same time attenuating the
other channel's signal, It makes it possible to give the sense of the information of the four
separated channels, so that according to the invention it is possible to obtain a near complete
presence of the sound originating from the four individual sound sources.
In the examples of FIGS. 7 and 9, each of the four speaker control circuits is stepped depending
on the magnitude of the respective signal, and each such bark circuit is compared to the other
three control circuits. Completely independent. Therefore, only one circuit can be turned on at
the same time. On the other hand, in the example of i'11 anti-1, each of the control circuits is not
completely independent and can not be controlled as finely as the upper side, but the
configuration can be greatly simplified. Although the case of stereo disc record has been taken as
an example of the recording medium for explaining the recording and reproduction technique as
described above, the present invention is not limited to the case of reproducing the disc record,
and the reproducing method of the present invention The same synthetic signal can be used to
process the same as the upper one, regardless of the recording medium which converts the
synthetic signal.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of an apparatus for
recording four channels of information in a stereo record, and FIG. 2 is left and right. A vector
diagram to illustrate the motion of the recording needle as it provides the center and difference
signals, and Figure 3 expands the four record grooves to illustrate the motion of the recording
needle in response to various signals. 4 is a schematic system diagram of a conventional stereo
reproduction apparatus designed to produce the sense of the third channel, and FIG. 5 is a
recording apparatus for recording 4-channel information in a 2-track stereo record. FIG. 6 is a
schematic diagram showing a record 牌 enlarged to explain the effect of supplying 11 difference
1 signals to both the left and right channels through the phase shift network, and FIG. 7 is a
channel according to the present invention FIG. 7A is a block diagram showing an example of the
configuration of a stereo reproduction apparatus, FIG. 7A is a circuit diagram of a portion
forming a transmission network in the apparatus shown in FIG. 7, and FIG. 8 is a transfer
characteristic of the logic circuit of FIG. Figure 9 is a curve diagram showing FIG. 10 is a block
diagram showing a preferred embodiment of the reproducing apparatus according to the present
invention, FIG. 10 is a characteristic curve diagram showing transfer characteristics of the logic
circuit of FIG. 9, and FIG. 11 is a block diagram showing still another embodiment of the present
invention. . 10 ...... stereo cutters, 12 ..... recording needle, 14 ...... master disk, 16 ...... signal
splitter, 1B ...... cartridge, 20 .......... · · · · · · · · · · Listeners 32 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · · · · · · · · · · · amplifier, 44, 46 · · · · · · · · · · · · dividers 48, 50, 52 ° 54 · · · ... Power
amplifier, 56.56 / ----- Logic circuit, 58.60 ..... Gain control amplifier, 59, 61 ..... Signal change
network, R1, R2, ... R3, R4 ······ Resistor, C1 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ... Control conductors 64, 66
·· · Common resistance, 86 ······ Wire, 8B, 90, 92, 94 · · · · Capacitor, 96, 98, 100, 102 · · · · · · Gain
control amplifier, 112, 114, 116, 118
··································································································································································· Adder 132 · · · · ·
· · · Phase inverter, 134 · · · · · · specific number circuit.
EndPage: 11