Every novice radio amateur after the first successful experiments, feeling the sweetness of his victories, wants to try to do something real. Not a toy, but a really working full-fledged thing. For this, a homemade simple headphone amplifier is perfect, which can be assembled with skillful hands in just a few minutes.
Where can I use it? Firstly, for its intended purpose, namely to amplify the signal from the tone block or preamplifier, that is, where the sound signal is too weak and it is impossible to connect headphones. In this case, you can make a headphone amplifier with your own hands. Secondly, it will come in handy as an additional tool. A portable headphone amplifier is quite applicable for testing circuits. After all, it often becomes necessary to find the place of the signal break in the new circuit that you have assembled, but it does not want to work in any way. For example, you made the same headphone amplifier with your own hands. He will help in finding the cause of the malfunction. With it, you can very quickly find the point at which the signal disappears. After all, this often happens because of a trifle: a part was badly soldered, a faulty capacitor, etc. Visually or with a testercause can be hard to find.
Making a headphone amplifier with your own hands is easy, because the mono circuit consists of only five parts. It is based on the TDA7050 chip, which costs 30-80 rubles. But, I think that in your stocks of radio components, which anyone who is passionate about this business always has, there is such a microcircuit. It was often used in cassette players and other simple sound-reproducing devices. You can also make a stereo headphone amplifier with your own hands on the same chip. To do this, you will have to add two polar capacitors to the output (you can use one common), and the input volume control can be made from a dual variable resistor.
The chip itself is a power amplifier in a normal size package (DIP8). Operating supply voltage from 1.6 to 6 volts. Consumes not much energy. The power of the output signal depends on the supply voltage. In the stereo version, with a load of 32 ohms and a voltage of three volts, you will get about 130 milliwatts of output on each channel. When connected via a bridge circuit in the mono version, the power is doubled. The output of the microcircuit is protected against short circuits. The circuit diagram is shown in Figure 1. The input signal is applied to pins 1 and 3, and headphones in 32 ohms are connected to pins 7 and 8. According to the specifications in bridged mode, the load should not be less than 32 ohms. To smooth the voltage, capacitors C1 and C2, 100 and0.1uF respectively. The resistance of the resistor R1 is 22 kOhm. Well, that's probably the whole description of our first model.
The second circuit in Figure 3 is often used in small-sized factory-made devices. Make it a little harder. The diagram shows all the necessary details. Figure 2 shows the same circuit for connecting speakers. As you can see, the difference is small. The circuit for the speakers uses polarized capacitors in each output channel, and for the headphones there is a common capacitor at the point where the circuit case is connected to them.
