THE DUO SCHEMES TO UMZCH

Analog IC К176ХА10 was developed as a combined that contains a standard power amplifier of sound frequency (umzch) and has long been undertaken by radio Amateurs on Board. With supply voltage 9 In it has an output of 0.7 W at the output, but… recommended by the manufacturers the option to include К176ХА10 has impressive size and value (with the condition playlist “bass”) is the oxide capacitor, the reliability of which by modern standards is poor.

 

Besides this element of capacity in the hundreds of thousands UF “sin” as it turned out, the tendency to create (under certain conditions and continuous operation) of a specific noise and interference. In addition — dry and, working in high current pass-through mode in series with the load, is the cause of the failures. Slightly lower reliability and electrolytic capacitors used in other circuits called amplifiers.

 

I developed technical solution allows to completely get rid of the above drawbacks. Its essence — to use another К176ХА10 and a low noise transistor (see figure). While umzch becomes a push-pull bridge. Reduced distortion, a twofold increase in power output, flattens the frequency response of the entire amplifier.

 

Dvuhmetrovy umzch is easy to build and almost no need for debugging (clarification denomination ragimzadeh resistor R2, that is, not count), and therefore can be recommended for independent production, even for novice hams. Because of the small energy consumption and, consequently, low power dissipation it is easy to do without forced heat dissipation. That is, the use of heat sinks on the chips is optional. Hence its small size and minuscule weight, allowing you to easily integrate such umzch gift in “talking” toys, music players, electronic musical instruments, or, conversely, to use as extra cascade in the amplification of signals from the line outputs of the various instruments.

 

In any case the device for proper operation will not fail. Input voltage audio frequency (e.g., electromagnetic sensor, musical instrument, or, say, an electret microphone) goes to the variable resistor R1. Of course, if the output of the signal source provided by the presence of a direct current component, to avoid galvanic coupling have to worry about the additional input of the separation of non-polar capacitor with a capacitance of 1 UF, conventionally not shown in the circuit diagram. Well, matter for by the amplifier.

 

Part of coming to umzch signal is removed from the slider of the variable resistor R1, through the dividing capacitor C2 is supplied to the base semiconductor triode VT1 and amplifies them. The capacitor C1 serves to “underscore” the upper audio frequencies and can be connected, if necessary, additional toggle switch or no.

 

Allocated to the emitter and collector loads of the transistor VT1 antiphase the signals arrive at the inputs of the circuits DA1 and DA2. After appropriate amplification of electric oscillations of audio frequency and serves for the dynamic head of BA1 or acoustic 4-16-Ohm system, where and converted into sound.

 

 

A circuit diagram of a simple and reliable power amplifier audio frequency transistor phase shifter, PCB and symbol mounted on it electronic components

 

Now some brief information about what other parts of this development. Capacitors C3 and C4 share a DC electric circuit, C5 and C6 to protect the inputs of the circuits from RF interference, C7 and C8 eliminate negative feedback in the respective circuits, C9 smoothes the load umzch in the field of ultrasound, and C10 — C14 are decoupling power. Potentiometer R1 plays the role of a volume control, the resistor R2 determines the operating mode of the transistor VT1 for DC; R3 and R4 are loads of the above-mentioned semiconductor triode respectively in collector and emitter circuits, R5 — balancing “podstreshny”, and the resistor R6 functions as the load for the ultrasonic vibrations.

 

For the installation of umzch is used PCB dimensions 60x50x1,5 mm of one-sided foil fiberglass, which is placed in a suitable sized case. The latter is a box with a lid, welded from strips of foil fiberglass, in this case is carried out and screening of umzch. Manufacturing technology of such structures has been maintained in the pages of “Modeller-designer” (see, for example, detailed in the publication No. 2’99 of the magazine). Quite acceptable as a housing and a plastic “camera” (of course, the screening here will be omitted).

 

In stereomerini recommended in the same housing to accommodate from two umzch. Input and output jacks, connectors, and terminals to connect the power supply and also the volume control is usually placed on its walls. Electrical connection units which are to be performed, typically by soldering, with a clever use of petals and blades, available in the details. It is not forbidden and installation of “wrap” (the material about it see in number 4 of the journal “modelist-Konstruktor” over the past year).

 

You can also perform inter-module connections using the multi-microfashion, allowing you to quickly change the composition of umzch. For example, as is often practiced for the combined active acoustic system, where each amplifier channel operates on its load.

 

Check umzch mounted and connected to a power source, is simple: at the touch to the entrance of a metal object (e.g. a screwdriver blade) the speaker or acoustical system must respond nicotinamidum sound — fire AC. The volume control R1 should be in the top (according to the circuit diagram) position.

 

Then, by submitting 10-100 Hz with a sound generator, or by using the same tip alternating current, is connected to the output umzch (parallel sound drivers or the sound system) avometr — in the measurement mode AC voltage with a limit of 1-1. 5 V. Moving the slider to the trimming resistor R5, set the maximum output voltage. And you can safely operate a homemade umzch.

 

The choice selection here is quite wide: chips К174ХА10 or equivalents — А283, R283, TDA1083 (the author used А283D); fixed resistors MLT-0,25, and the like: “podstreshny” SDR-38; constant of non-polar capacitors KM; polar oxide K50-12, K50-35 or imported, compact; transistor КТ3102 with any alphabetic index… selection Criterion named the semiconductor triode is simple — when the supply voltage 9 V collector current VT 1 must be equal to 0.5 mA. You want the load resistance of umzch was in the range of 4-16 Ohms if you change the power supply 6 to 9 V and in the range of 8-16 Ohms for 12-volt source.

 

Homemade umzch is desirable to feed from the network using the stabilizer with a small ripple. In the simplest case, can be completely satisfied with what he provides, for example, the chip ROLL-8 for stationary conditions, or to use the compact sources of electricity (galvanic battery, batteries) on the road. In the application of umzch in the car, it is desirable to carry out the power supply from the onboard network, but only via electronic stabilizer (e.g., on the chip series КР142), and standard automotive electrical filter that protects any radio interference from spark ignition systems.

 

To increase sound pressure in a stationary mode it is recommended as a load use acoustic systems with non-compression drivers. These speakers are usually impressive outdoor dimensions and large diameters of the cone dynamic drivers. And since the chip in the design of umzch combined, with redundant capabilities, to the extent it makes sense to focus on perfecting this home-made, additionally collecting on unused “electronics”, for example, the receivers thus becoming the owner of a small radio station.

 

V. BESEDIN, Tyumen