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BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a conventional amplifier,
and FIG. 2 is a block diagram of an embodiment of the present invention. 3.4 · · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · · phase inversion circuit, S ˜ ˜ . ······ Switch.
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement
of a stereo amplifier having preamplifiers for left and right channels and power amplifiers. Oh, 妬
fyi shiro, i! 4Q · Pickled. As shown in FIG. 1, the 8 + ψ dull / general stereo amplifier is roughly
divided into left and right channels, respectively, and has a configuration of a preamplifier 3.4
and a power amplifier 5.6. The left channel signal and the right channel signal are input to drive
the speaker 7.8. Also, in the 3D (3 Dimension) method, the frequency signal of extremely low
frequency is taken out from the reproduced signals of both channels by the low pass filter 9, and
the dedicated speaker (woofer) 11 is driven by the dedicated amplifier 10 (good with monaural
amplifier). There is a method. This is in the form of adding a system surrounded by a dotted line
to a normal stereo device. This method is based on the idea that even a single woofer is sufficient
because there is no directivity for ultra low frequencies (for example, 100 Hz or less), and the
woofer should be dedicated to reproduction of only ultra low frequencies. Can be used only in
the range of piston motion, and distortion etc. is improved. In addition, the left and right channel
speakers 7.8 need only reproduce the middle to high frequency range, and the damper, edge,...
As the non-linear distortion does not appear on the cone paper itself, the sound does not get
noisy. Furthermore, since only two left and right channels are required in the 3D system, one
woofer can be used. Therefore, when the left and right channel speakers are multi-channeled,
respectively, the performance can be expected to be equal or better than the low cost. In such a
3D system, it is preferable to drive with woofers and powers as with multi-channels. In the past,
for this reason, an IBORW monaural amplifier was used for the center channel. This invention is
to provide a stereo amplifier which can be arbitrarily selected to be used as a 3D system center
channel amplifier as described above or as a normal stereo amplifier, and at the same time high
power can be realized. It is the purpose. FIG. 2 is a block diagram showing an embodiment of the
present invention, wherein 1.2 is an input terminal, 3.4 is a preamplifier, 5.6 is a power amplifier,
7.8 is a speaker, 9b, 1 is an island. Dimension · 7 °. Is a low pass filter, 12 is a phase inverting
circuit, 13.14 is an output terminal of a preamplifier 3.4, 15.16 is an input terminal of a power-7
amplifier 5.6, and 17.18 is a power amplifier 5.6. The output terminals S1, S2, S3 and S4 are
interlocking changeover switches, S and S are variable loudspeakers constituting interlocked
loudspeaker switching switches and R1 and R2 mixing circuits, respectively.
In such a configuration, when each of the changeover switches 88 to S6 is on the contact a side
as shown in the drawing, it becomes a configuration of a normal stereo amplifier, and the left
signal is input terminal 1 → preamplifier section 3 → switch switch S → → switch S2 → power
amplifier unit 5 → output terminal 17 → spicuff → switch S → → ground signal is transmitted in
the order, the right signal is input terminal 2-preamp unit 4-switching switch S S4-switching
switch S4 → power amplifier unit The signal is transmitted in the order of 6 → output terminal
18 → speaker 8 → switch S6-earth, and is reproduced in stereo. Next, when the changeover
switch 5l-84 is switched to the contact 6 side and the speaker changeover switches S, S, and S
are also switched to the contact 6 side, the left and right channel 7 from the input terminals 1
and 2 are output. The low frequency signal is mixed by the variable resistors R1 and R2 at an
appropriate ratio, only low frequency components are input to the power amplifier unit 5 and the
phase inverting circuit 12 by the low pass filter 9, and the speaker 7 is the power amplifier unit
5.6. Driven by In this case, the circuit becomes a 3D system center channel amplifier and works
as a BTL (BalancedTransformerless) connection. Therefore, it operates as a monaural amplifier,
which is about twice as high power as the stereo amplifier, and can sufficiently drive W -..- for
the center channel. In this case, separate speakers may be connected between the output
terminals 17. 18 instead of the speaker 70. In addition, power amplifiers and speakers are
separately connected to the output terminals 13.14 for left and right channels. As described
above, when a normal stereo amplifier is used as a 3D system center channel amplifier, the
amplifier units of both channels can be effectively used because it can be realized by BTL
connection. The cut-off frequency of the low pass filter 9 is preferably about 50 to 70 Hz, and the
steepness of the attenuation characteristic is also two. ρ, S is desirable. Furthermore, in the
embodiment of FIG. 2, an パ ス pass filter may be inserted in the human power in the left and
right channel amplifiers connected to the output terminals 13.14. As described above, according
to this invention, the following effects can be obtained. (A) When the stereon stem is developed
into a 3D system, it can be used simply as a center channel / with only switch switching. (B)
When used in the 3D system, the amplifier sections of both channels are used to drive power,
which is good for driving a 3D woofer.
← → In the case of 3D system with this amplifier, you only need to add one stereo amplifier or
two monaural amplifiers, and you don't need much power.