JPH02165798A - Stereo headphone driving device - Google Patents

Abstract

PURPOSE:To adjust boosting quantity in a low band and to make it difficult to generate a distortion by providing a stereo headphone driving device with one variable resistor to vary the level of the output signal of a low-pass filter, which is used as a phase adjuster in common, and input the varied output signal to a third power amplifier. CONSTITUTION:When a mixed signal (c) of the respective outputs of buffers 12L and 12R is passed through a low-pass filter/180 deg. and phase inverter 11, the phase of the signal (c) is shifted at 180 deg., and the phase of output signals (d), d', and (e) of the low-pass filter/180 deg. and phase inverter 11 becomes the opposite phase to the phase of the mixed signal (c). Consequently, in a boosting band (low band), the sum of a level absolute value in respective output signals (b) and b' of first and second power amplifiers 8 and 9 and another level absolute value in an output signal (e) of the third power amplifier 10 is to be applied to both edges of respective speaker units 1L and 1R of a stereo headphone 1, and low-band boosting can be attained. Further, a signal level at the input side of the third power amplifier 10 can be adjusted only with 61 variable resistors having the low band boosting quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a stereo headphone drive device used in headphone stereos, tape recorders, and the like.

2. Description of the Related Art In recent years, the spread and growth of headphone stereo has been remarkable. When listening to music with stereo headphones, one way to enjoy it is to boost the low and high frequencies using a so-called graphic equalizer.

An example of a conventional stereo headphone drive circuit that performs low frequency boost and can vary the amount of boost will be described below with reference to the drawings.

FIG. 2 shows a conventional stereo headphone drive circuit, which includes a variable circuit for adjusting the amount of low-range boost. In FIG. 2, 1 is a stereo headphone, to which common terminals 12 of left and right speaker units IL and 1H are connected. 2.3 is a power amplifier, the output of each of which is applied to each input terminal 13L, 13H of the stereo headphones 1. 4°6 is a low-range boost amplifier that boosts only the low range, 6L and 6R are variable resistors for the low-range boost amount, and 7L is provided to vary the amount of boost.

7R is a volume variable resistor.

In such a configuration, the left and right signals, which are stereo signals, are input to the input terminals 14L and 14H, are boosted in the low range by the low range boost amplifiers 4 and 6, and after the boost amount is adjusted by the variable resistors sL and aR. , the volume is adjusted to an appropriate volume via variable volume resistors 7L and 7R. Next, the power amplifier 2.3 amplifies the entire sound range and adds it to the stereo headphones 1 to drive the stereo headphones. By boosting the low range in this way and varying the amount of boost to your liking, you can enjoy music reproduction.

Problems to be Solved by the Invention However, in the above conventional configuration, the variable resistors sL and eR are increased in order to vary the amount of low-frequency boost.

Two are required for each channel and channel of R, and since the low frequency boost is boosted by low frequency boost amplifiers 4 and 6, it is easy to reach the saturation level of the power amplifier, and the dynamic range cannot be widened.
In particular, when the volume variable resistors 7L and 7R are adjusted to a high level, there is a problem in that the low frequency range is distorted.

In view of the above-mentioned problems, the present invention provides a stereo headphone drive device that uses three power amplifiers to perform low-frequency boost, requires only one variable resistor, and can adjust the amount of low-frequency boost for each H channel. It provides:

Means for Solving the Problems In order to solve the above problems, the stereo headphone drive device of the present invention includes a first power amplifier whose output is connected to an input terminal of either the left or right signal of the stereo headphones; A second power amplifier connected to the other input terminal of the stereo headphones, and a third power amplifier whose output is connected to the common terminal of each speaker unit of the stereo headphones, input a mixed signal of left and right signals. and one variable resistor that varies the level of the output signal of the low-pass filter and phase adjuster and inputs it to the third power amplifier. .

According to the present invention, with the above-described configuration, it is possible to adjust the amount of low-range boost of each channel/V signal of I, H, and H using only one variable resistor. By inputting the signal to the third power amplifier via the power amplifier, the saturation level can be expanded up to twice depending on the low frequency, making it possible to widen the dynamic range. Therefore, distortion is less likely to occur when boosting the low range.

Embodiments Hereinafter, stereo headphone drive circuits according to embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the invention. In Figure 1, 8
, 9.10 are respectively the 11th and 2nd . 3rd power amplifier, 11
12L is a low-pass filter and 180-degree phase inverter provided before the third power amplifier 13.

12R is a buffer 1 located before the input of the low-pass filter and 180-degree phase inverter 110 and transmits the signals of both R channels without attenuation.

Next, the operation will be explained. The input left signal a and right signal a/, the first . The output signals S and b' of the second power amplifier 8.9 are in phase. In addition, it also serves as a low-pass filter and a 180
The output signal d of the degree phase inverter 11.

The output signal d' of the variable resistor 6 and the output signal e of the third power amplifier 1o are in phase. Buff 112L, 12
The mixed signal C of each output of R passes through a low-pass filter and 180-degree phase inversion RF511, so that the phase thereof is shifted by 180 degrees. As a result, for the mixed signal C, the output signals d, d',
e has an opposite phase. Therefore, in the boost band (low range), the absolute value of the level of each output signal S, b' of the first and second power amplifiers 8.9 and the level of the third power amplifier 1
The sum of the absolute values of the levels of the output signal e of the stereo headphone 1 is applied to both ends of each speaker unit IL and IR of the stereo headphone 1, making it possible to boost the low frequency range. In the above process, the signal level on the input side of the third power amplifier 1o can be adjusted using only 61 variable resistors of low frequency boost amount. Therefore, on the output side of the third power amplifier 1o, the first
, each output signal of the second power amplifier 8.9, b'
You can also adjust the output level of the reverse phase and the amount of boost in the low range. Furthermore, if the absolute values of the output levels on the output side of the first and second power amplifiers 8 and 9 and the output level on the output side of the third power amplifier 1o are equal, the level applied to the speaker unit will be equal to that of one speaker unit. This means that the saturation level of the power amplifier will be doubled, and the dynamic range will also be expanded.

Effects of the Invention As described above, the present invention includes a first power amplifier whose output is connected to one of the left and right input terminals of stereo headphones, and a second power amplifier whose output is connected to the other input terminal of the stereo headphones. A power amplifier, a third power amplifier whose output is connected to the common terminal of each speaker unit of the stereo headphones, a low-pass filter and phase adjuster that receives the left and right mixed signals as input, and this low-pass filter and phase adjuster. By including one variable resistor that varies the level of the output signal of the regulator and inputs it to the third power amplifier, the amount of boost in the boost band (low range) can be controlled with only one variable resistor. It can be adjusted and the dynamic range can be expanded up to twice. Therefore, it has the advantage that distortion is less likely to occur when boosting the low range.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing an embodiment of the stereo headphone driving device of the present invention, and FIG. 2 is a circuit block diagram showing a conventional stereo headphone driving device. 1... Stereo headphones, 6... Variable resistor, 7L, 7R... Volume variable resistor,
8...First power amplifier, 9...Second power amplifier
Power amplifier, 10...Third power amplifier, 1
1...Low frequency filter and 180 degree phase inverter, 1
2...Buffer. Name of agent: Patent attorney Shigetaka Awano and one other person

Claims (1)

[Claims] a first power amplifier whose output is connected to one of the input terminals of the left and right signals of the stereo headphones; a second power amplifier whose output is connected to the other input terminal of the stereo headphones; A third power amplifier whose output is connected to the common terminal of each speaker unit, a low-pass filter and phase adjuster that receives a mixed signal of left and right signals, and the level of the output signal of this low-pass filter and phase adjuster. and one variable resistor that varies and inputs the variable to the third power amplifier.