JPH026715Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention This invention relates to a sound reproduction device equipped with a parallel power amplifier capable of stereo operation, and particularly relates to an improvement of the monaural reproduction section thereof.

Technical background of the invention In general, low power supply voltage audio equipment that uses batteries as a power source, such as portable radio receivers, often employs a so-called BTL circuit to increase the output, especially during monaural playback. .

That is, this is such that parallel power amplifiers capable of stereo operation are driven in antiphase relation to each other.

Problems with the Background Art However, in the conventional sound reproduction device as described above, a phase inverting amplifier is required to drive the parallel power amplifiers in an antiphase relation to each other during monaural reproduction, so the configuration is accordingly complicated. However, it has the disadvantage of increasing costs due to

Furthermore, in order to switch between stereo playback and monaural playback, it is necessary to provide a large number of switches to switch each input section and output section of the parallel power amplifier, which also complicates the configuration and increases costs. This became a drawback.

Purpose of the invention This invention was made in view of the above points, and is intended to simplify the configuration of the monaural playback section and the monaural playback/stereo playback switching section in devices equipped with parallel power amplifiers capable of stereo operation. It is an object of the present invention to provide an extremely good sound reproducing device which can contribute to cost reduction as much as possible, and which has an improved balance volume circuit section.

Summary of the invention In other words, the sound reproduction device according to this invention connects between each output section of a parallel power amplifier capable of stereo operation.
A speaker dedicated to monaural reproduction, which has two types of voice coils wound in the direction in which the magnetic fluxes generated by the voltages of the in-phase components applied separately are added together, is connected, and each input section of the parallel power amplifier is connected to the speaker. It is characterized in that overdrive prevention resistors are inserted and connected between both ends of the balance volume variable resistor.

Embodiment of the invention First, a basic example of the invention will be explained with reference to FIG.

In other words, the input ends of the left and right channels L and R
IN _L and _INR are directly connected to respective input sections of power amplifiers 11 and 12, respectively. These power amplifiers 11 and 12 each have a capacitor at their output section.
C ₁ or C ₂ and the stereo playback side contacts a, a' of the monaural playback/stereo playback selector switch S ₁ or S ₂
By being connected correspondingly to each voice coil 131, 141 of the speaker 13 or the second speaker 14, a parallel relationship is established so that stereo operation is possible without providing any switching means at the input section. There is.

Furthermore, the parallel power unbreaders 11 and 12 capable of stereo operation are connected between their respective output sections via respective monaural playback side contacts b and b' of the monaural playback/stereo playback switching switch _S1 or _S2 , which will be described later. By being connected to the first or second voice coils 151, 152 of the third speaker 15 dedicated to monaural reproduction, a phase inverting means is provided for making the phase relationship opposite to each other during monaural reproduction. A large output equivalent to that of BTL drive can be obtained without any need for it.

Here, the third speaker 15 exclusively for monaural reproduction has two types of voice coils 151 and 152 wound in directions in which the magnetic fluxes generated by the in-phase component voltages applied to each are added to each other. It is configured.

In the above configuration, when the stereo playback/monaural playback switching switches S ₁ and S ₂ are set to the stereo playback side contacts a and a', the first and second speakers 13 for the left and right channels L and R are set to the stereo playback side contacts a and a'. , 14 _{, P L =} V _L ² /R _L1 P _R =V _R ² /R _L2 , and performs normal stereo operation.

In this case, V _L and _VR are each power amplifier 11, 12
R _L1 and R _L2 are the impedances of the voice coils 131 and 132 in the first and second speakers 13 and 14, respectively.

Furthermore, when the stereo playback/monaural playback switching switches S ₁ and S ₂ are set to the monaural playback side contacts b and b', the output P _M from the third speaker 15 dedicated to monaural playback is P _M =V _L ² /R _L /2+V _R ² /R _L /2=2(V _L ² +V _R ² )/R _L , and since V _L and V _R are in phase and at the same level, P _M = 4V _L ² /R _L = 4V _R ² /R _L , which produces monaural playback that produces a large output equivalent to that when driven by BTL.

In this case, (R _L /2) is the impedance of the two types of voice coils 151 and 152 in the third speaker 15, which has a single voice coil like the first and second speakers 13 and 14. The impedance is 1/2 that of a normal speaker.

By the way, in the sound reproduction device according to the basic example described above, a variable resistor serving as a balance volume for stereo reproduction is connected between each input section of the parallel power amplifiers 11 and 12 during monaural reproduction. If the device 16 were to be fully constricted to one of the channels, the channel on the constricted side would be completely inoperable.

In other words, this is compared to a state in which the variable resistor 16 for the balance volume is placed at the midpoint because the input section of the power amplifier 11 or 12 on the narrowed-down channel side is grounded in an AC manner. In this case, only half of the output is output from the third speaker 15.

Therefore, if you want to listen at the same sound pressure level as when both channels are operating, the power amplifier 12 or 11 on the side of the channel that is not throttled must output twice as much power as it normally does, so it will be in an overdrive state. This is not desirable.

Next, an embodiment of this invention which takes into consideration the problems of the above-mentioned basic example will be described in detail with reference to FIG.

That is, as shown in Fig. 2, L _g ,
Left and right channel signal sources 21 and 22 having an internal impedance of R _g are connected to respective input sections of a pair of left and right power amplifiers 23 and 24, respectively.

And the pair of left and right power amplifiers 23, 24
A variable resistor 25 for balance volume is connected between each input section via resistors R ₁ and R ₂ selected to have predetermined values as described later, and capacitors C ₁ and C ₂ are connected between each output section. A speaker 26 is connected via.

Here, the speaker 26, like the third speaker 15 in the basic example, is equipped with two types of voice coils wound so that the respective magnetic fluxes generated by the in-phase voltages applied to each are added together. be.

In addition, each input section of the pair of left and right power amplifiers 23 and 24 and a balance volume variable resistor 25 are connected to each other.
It is assumed that the resistors R ₁ and R ₂ inserted and connected between both ends have a maximum amount of unbalance required during stereo operation.

Note that the slider of the balance volume variable resistor 25 and the middle point of the voice coil portion of the speaker 25 are both grounded.

According to the above configuration, even if the balance volume variable resistor 25 is narrowed down to either the left or right channel, the maximum voltage is applied to the input section of the power amplifier 23 or 24 on the narrowed channel side. Then, an input signal of R ₁ /R _g +R ₁ V _R or R ₂ /L _g +R ₂ V _L will be supplied.

Here, V _L and V _R are the signal source 2 of the left and right channels.
1 and 22, and normally V _L =V _R. By setting R ₁ = R ₂ , each output P _L of both left and right channels during stereo operation is
Speaker 2 that produces a superimposed output P ₀ (=P _L +P _R ) of P _R
From 6, P _L = P _R even during monaural operation.
By doing so, an output with the same sound pressure level as in normal times, P ₀ = 2P _L = 2P _R , will be output.

In other words, by inserting resistors R ₁ and R ₂ in addition to the effects of the basic example, even if the balance volume variable resistor 25 is set to either channel side during monaural operation, the left and right pair of power amplifiers 23 or This prevents one of the power amplifiers 24 from becoming inoperable, and furthermore prevents the active power amplifier 23 or 24 from going into an overdrive state.

It goes without saying that this invention is not limited to the one embodiment described above and illustrated, and that various modifications and applications can be made without departing from the gist of this invention.

Effects of the invention Therefore, as detailed above, according to this invention, a phase inversion means for driving BTL during monaural reproduction and an input section switching means for switching between stereo reproduction and monaural reproduction for a parallel power amplifier capable of stereo operation are provided. The balance volume circuit section has been improved so that it can contribute to cost reduction with a simple configuration that is unnecessary, and that both channels can operate together regardless of the position of the balance volume during monaural operation. A sound reproduction device can be provided.

[Brief explanation of the drawing]

FIG. 1 is a structural explanatory diagram showing a basic example of a sound reproducing device according to this invention, and FIG. 2 is a structural explanatory diagram showing an embodiment of a sound reproducing device according to this invention. 21, 22...Signal source, 23, 24...Power amplifier, 25...Balance volume variable resistor, 26...Speaker, _R1 , _R2 ...Resistance.

Claims (1)

[Scope of utility model registration request] A pair of power amplifiers arranged in parallel to each other to enable stereo operation, a pair of stereo playback/monaural playback switching switches connected to each output section of the pair of power amplifiers, and a pair of stereo playback/monaural playback switching switches connected to each output section of the pair of power amplifiers. It is connected between a pair of left and right channel speakers connected to each stereo playback contact side of the switch, and each monaural playback contact of the pair of stereo playback/monaural playback selector switches. a speaker having two types of voice coils wound in a superimposed manner; a pair of resistors for preventing overdrive on one side, one end of which is connected to each input section of the pair of power amplifiers;
A sound reproduction device comprising a balance volume variable resistor connected between the other ends of the pair of resistors.