JPH0783519B2 - Stereo headphone drive - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stereo headphone driving device used in a headphone stereo, a tape recorder, or the like.

2. Description of the Related Art In recent years, the growth of headphone stereos has been remarkable, and the number of opportunities to enjoy music sources with stereo headphones has increased. The way people enjoy music sources is diversifying.

Hereinafter, as a conventional technique, an example of a stereo headphone driving circuit for low-frequency boosting will be described with reference to the drawings.

FIG. 2 is a circuit block diagram showing an example of a conventional stereo headphone drive circuit, in particular, one in which a low frequency boost circuit is incorporated. In FIG. 2, 1 and 2 are power amplifiers, 3 is stereo headphones connected to and driven by the outputs of the power amplifiers 1 and 2, 4,5 are power amplifiers for boosting low frequencies, and front of 1 and Reference numeral 6 denotes a low frequency boost amplifier which is provided as a circuit and amplifies only the low frequency band, and 6 denotes a volume control. With the above configuration, the signals input from both the L and R channels are amplified only by the low frequency boost amplifiers 4 and 5, and are adjusted to the desired volume by the volume control 6 and then by the power amplifiers 1 and 2. The voltage and power are amplified over the entire band and given to the stereo headphones 3, and the stereo headphones are driven. Therefore, the low frequencies of the music source can be reproduced richly and enjoyed with stereo headphones.

Problems to be Solved by the Invention However, in the above configuration, the low-frequency boost circuit 4,5
Since the low-frequency signal is amplified by, it is easy to reach the saturation level of the power amplifiers 1 and 2, and there is a problem that low-frequency distortion is audible especially when the volume control 6 is set high.

In view of the above problems, the present invention provides a stereo headphone drive device that is less likely to be distorted even when low-frequency boosting is performed using a power amplifier having the same saturation level.

Means for Solving the Problems In order to solve the above problems, the stereo headphone driving device of the present invention has three power amplifiers and a filter / phase adjusting circuit, and outputs the first and second power amplifiers. The output of the third power amplifier is connected to the common terminal which is connected to the L channel terminal and the R channel terminal of the stereo headphones, respectively, and is made common via each speaker unit of the stereo headphones. The input signal is provided with the in-phase components of the L and R channels through the filter / phase adjusting circuit.

Operation According to the present invention, since the band according to the characteristics of the filter / phase adjusting circuit is boosted by the third power amplifier by the above-described configuration, the voltage is doubled at maximum (6 dB) depending on the boost amount. It is possible to extend the saturation level up to. Therefore, even if boosting is performed, distortion will be less likely to occur.

Embodiment Hereinafter, a stereo headphone drive circuit according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 (a) is a circuit block diagram showing an embodiment of the present invention. In FIG. 1 (a), 7, 8 and 9 are respectively the first and the first.
Second and third power amplifiers, 10 is a filter and phase adjusting circuit provided as a front circuit of the third power amplifier, 1
Reference numerals 1, 12 and 13 denote L channels, R channels and common terminals of the stereo headphone 3, respectively, and 14 denotes a mixing circuit for taking out in-phase components of output signals of the first and second power amplifiers 7 and 8.

FIG. 1B is a circuit block showing the filter / phase adjusting circuit 10 more specifically. In FIG. 1 (b), 10-A and 10-C are attenuation type low-pass filters, and 10-B is an in-phase amplifier. 1 (a) and 1 (b), each point on the circuit is represented by a, a ', b, b', c, d, e, as shown in the figure.
Define as f and g.

The operation will be described below with reference to the drawings.

Points a, a 'and b, b' and d are in phase. The points e and c are also in phase. Attenuated low pass filter 10-A,
10-C is composed of a CR filter, and is sufficiently attenuated even in the boost band (low range) from the pointers d to f and g to e, so that the phase is delayed by about 90 °. Since there is a common-mode amplifier 10-B between 10-A and 10-C, the phase is delayed by about 180 ° in the process from point d to point e. As a result, the points b, b'and c have opposite phases, so b, b'in the boost band (low range).
The sum of the absolute value of the voltage at 1 and the absolute value of the voltage at c is applied to both ends of each speaker unit of the stereo headphone 3, and low-frequency boosting is possible. The power amplifiers 7, 8, 9 have the same saturation level, but the third power amplifier 9 has the first and second power amplifiers 7,
Since it operates in the opposite phase to 8, if the absolute values of the levels of points b, b'and c are equal, the saturation level will be doubled (6 dB increase) considering both ends of the speaker unit.
It will be.

As described above, according to the present embodiment, the three power amplifiers and the filter / phase adjusting circuit are provided, and the output of the third power amplifier is connected to the common terminal of the stereo headphones, and the filter which is the pre-circuit thereof is provided. Set the input of the dual phase adjustment circuit to L,
By adopting a configuration that takes in-phase components of both R channels, it is possible to obtain an effect that distortion is unlikely to occur even if low frequency boost is performed.

As described above, the present invention has three power amplifiers and a filter / phase adjusting circuit, and outputs of the first and second power amplifiers are connected to the L channel terminal and the R channel terminal of the stereo headphones, respectively. The output of the third power amplifier is connected to the common terminal that is shared via each speaker unit, and its input signal is given the in-phase components of the L and R channels via the filter and phase adjustment circuit. By doing so, the power amplifier saturation level in the boost band can be expanded by up to 6 dB (voltage ratio), and distortion can be reduced.

[Brief description of drawings]

FIG. 1 (a) is a circuit block diagram of an embodiment of a stereo headphone driving device of the present invention, and FIG. 1 (b) is a circuit block diagram more specifically showing one block of FIG. 1 (a). FIG. 2 is a circuit block diagram showing a conventional stereo headphone driving device. 7,8,9 …… First, second and third power amplifiers, 10 …… Filter and phase adjustment circuit.

Claims (1)

[Claims] 1. A first power amplifier supplied with an L channel signal, a second power amplifier supplied with an R channel signal, and a mixing circuit for extracting an in-phase component of the L channel signal and the R channel signal. , A filter / phase adjusting circuit for passing a low frequency component from the output signal of the mixing circuit and inverting the phase of the signal, and a third power amplifier to which the output signal of the filter / phase adjusting circuit is supplied, The L channel terminal and the R channel terminal, to which the outputs of the first and second power amplifiers are connected, are connected to one terminal of the first and second speaker units of the stereo headphone, respectively. Connect the other end of the second speaker unit to the common terminal commonly
A stereo headphone driving device, characterized in that the output of the power amplifier is connected.