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The universal low-frequency amplifier can have a number of applications, especially in homes with modern sound systems. It can be used, for example, as an amplifier for a microphone, turntable, tuner, tape deck, etc. Another example of the application of such an amplifier - in a telephone set for a tape recorder.
The amplifier circuit consists of a transistor preamplifier and a power amplifier with integrated circuit UL1481. The preamplifier has two inputs: one with high sensitivity and low impedance for a dynamic microphone and another with low sensitivity and high impedance for other signal sources. Potentiometer R11 is used to adjust the volume.
It is important to remember that a shielded cable must be used for all longer connections to send a signal to the amplifier. This also applies to the connection of the potentiometer (in this case this condition will not be necessary)
The amplifier must be powered by batteries or other voltage source 6 ÷ 9V. The output power depends on the speaker voltage, supply voltage, and output power. For example, at full output, 6V supply voltage and 4Ω speaker resistance, this power will be 3W.
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