JPH0136349Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial field to which the invention pertains) This invention relates to an expansion circuit for an audio amplifier.

(Prior art) As shown in Fig. 5, the conventional expansion circuit uses a bridge T-type RC filter circuit in the feedback circuit β ₂ of the feedback circuit tuning method selection amplifier, and keeps the tuning frequency f ₀ of the filter circuit constant. Alternatively, it could be changed manually.

(Purpose of the invention) This invention develops the conventional expansion circuit described above to create a system for audio amplifiers that can be used in audio amplifiers to create a sense of aural reality that has not existed in the past. The purpose is to provide an expansion circuit.

(Structure, function, and effect of the invention) As explained in the block diagram of FIG.
A type RC filter circuit 2 was used in the feedback circuit β ₁ of the feedback circuit tuning method selection amplifier 1, and the low frequency component of the input signal e _i , for example, the frequency component of 1 KHz or less, was controlled by the rectified DC voltage e _d . This configuration is characterized by the following.

The DC voltage e _d is determined by a voltage doubler rectifier circuit Re including a buffer amplifier A ₂ , a bandpass filter/amplifier A ₃ in the frequency band of 10Hz to 1KHz, and diodes D ₁ and D ₂ as shown in the embodiment in FIG. , is obtained as the output voltage of the control voltage generating circuit 4 consisting of a time constant circuit T including a resistor R ₃ and a capacitor C ₃ , and is inputted to the control terminal C of the feedback circuit β ₁ . This DC voltage e _d is
This voltage is similar to the envelope of a signal with a frequency band of 10Hz to 1KHz, and is proportional to the amplitude of the low frequency component signal.

When the feedback circuit β ₁ is the embodiment shown in Fig. 2, the tuning frequency ₀ and the amplification degree _{a 0 of} the amplifier A ₁ at this tuning frequency ₀ are determined by
R _QThen , if we set R _Q + R ₂ = Rx and C ₁ = C ₂ = C, then a ₀ = 1 + R ₁ /2Rx...(1) Therefore, there is a relationship between the amplification degree a ₀ and the tuning frequency ₀ as follows: a ₀ =1+(√2CR _{1 0} ) ² (3).

Equation (3) shows that as shown in Figure 4, as the resonance frequency ₀ increases, the amplification degree a ₀ also increases;
This shows that as ₀ becomes lower, the amplification degree a ₀ approaches 1.

This devised audio amplifier expansion circuit is the third
When used in a two-channel stereo amplifier and assembled into a stereo device as shown in the figure, the following effects are produced. As the signal level of the low frequency component of the music signal gradually increases, the DC voltage e _d gradually increases, and the tuning frequency of the feedback circuit tuning method selection amplifier 1, 1' controlled by this DC voltage e _{d becomes 0} ,
₀ ′ and the amplification degree at this tuning frequency ₀ , ₀ ′
Both a ₀ and a ₀ ′ gradually become larger. Next, when the signal level of the low frequency component gradually decreases, the DC voltage
e _d gradually decreases, and along with this, the tuning frequency
₀ , ₀ ′ and the amplification degrees a ₀ , a ₀ ′ gradually become smaller.

When listening to reproduced sound in such a state, the listener will experience the stereo effect of a conventional two-channel stereo system, as well as a certain kind of effect in which the listener feels as if the sound is approaching from a distance, or as if it is receding from a distance. This gives a sense of realism to the bass range reproduction, giving it a powerful and dynamic effect that makes it seem like it is approaching the listener.

[Brief explanation of the drawing]

Figure 1 is a block diagram explaining this idea, Figure 2
The figure is a circuit block diagram showing an embodiment of this invention, Fig. 3 is a circuit block diagram showing another embodiment of this invention, Fig. 4 is a characteristic diagram of the embodiment, and Fig. 5 is a circuit block diagram showing a conventional example. Figure. A ₁ , A ₂ ... Both amplifiers, A ₃ ... Band pass filter and amplifier, Re ... Rectifier circuit, T ... Time constant circuit, β ₁ , β ₂ ... Both feedback circuits, 1 ... Feedback circuit tuning Method selection amplifier, 3...Voltage controlled variable resistance circuit.

Claims (1)

[Scope of utility model registration request] A bridge T-type RC filter circuit using a voltage-controlled variable resistance circuit as a parallel connected element was used in the feedback circuit of a feedback circuit tuning method selective amplifier, and the low frequency component of the input signal was controlled by a rectified DC voltage. An expansion circuit for audio amplifiers featuring the following features.