Listening to music with headphones, especially small headphones, always feels that the music taste is not enough, and the effect in the low frequency band is even worse. Therefore, using this machine to enhance the low-frequency characteristics of the earphones, and adopting the method of stereo anti-phase synthesis, plus the built-in simple matrix surround sound circuit, can obtain strong bass and widen the sound range in a wider range. This unit is called Super Square Effect. This gripping power is no less than live stereo.
1. The working principle of the circuit
The circuit principle is shown in Figure 34.
A low-frequency enhancement circuit composed of resistors and capacitors. Use the feedback input of the power amplifier IC to form a stereo anti-phase synthesis circuit. Use the power amplifier IC to form the driving circuit of the headphone. The resistance and capacitance between the input ICs can enhance the low-frequency characteristics, because the potentiometer is added, and the enhancement of the low-frequency part can be continuously adjusted between 0-10 times. Stereo inverting synthesis circuit IC After the DC coupling capacitors on pin 2 and pin 8, it is composed of 0.47µF and 50K potentiometers. In this circuit, the left and right parts of the treble part in the square effect component of the stereo sound are reversed and then synthesized to enhance the effect. Push the headset with Toshiba TA7376P. This IC has two built-in channels with few external components and can work at low voltage. When the load impedance is low, it can reproduce the low-frequency sound with moving effect. If the power supply is changed to 5# batteries, use four in series with a voltage of 6V, which can directly drive high-output speakers. Better results can be obtained by adding three 200µF/10V capacitors to around 1000µF.
2. Selection of components
All components are nothing special. Use monolithic capacitors for 0.1µF and 0.47µF capacitors, and electrolytic capacitors for others. Among the potentiometers, 20K is a double-connected potentiometer, and 50K is a potentiometer with a switch. There are no special requirements for resistors, and ordinary 1/8 or 1/4W metal film resistors are used. The plug uses a stereo plug.
3. Production and debugging method
It's so easy to make, even for beginners, one day is enough. Pay attention to the polarity of the pins of the IC and the electrolytic capacitor. The wiring of the potentiometer is messy, don't get it wrong. As long as there are no wiring errors and bad soldering, it will be successful in no time. Plug in stereo headphones or ordinary headphones, insert batteries, and turn on the switch. If the two knobs cooperate well, you can get extremely moving effects when listening to music. Make appropriate adjustments according to the music you listen to and the sound source. This is the main point of using this machine. Needless to say, even better results will be obtained in connection with small stereos, TVs, and CDs.