Amplifier with switchable gain. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Transistor power amplifiers
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The switchable gain amplifier can be widely used in public address systems. Such amplifiers in silent mode must provide suppression of spurious interference. For this purpose, a threshold device is introduced into the circuit, which changes the gain of the amplifier from minimum to maximum when the level of the low-frequency signal exceeds the level of existing interference by a given number of times.
The threshold device circuit shown in the figure contains a low-frequency threshold amplifier, a peak detector, and an electronic key.
The circuit should produce switching gain without clicks and without perceptible distortion of the speech signal. A diagram of a device based on an operational amplifier equipped with a threshold device is shown, which changes the gain from unity to nominal when the voltage at its input exceeds 30 mV.
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| Random news from the Archive soulution 511 stereo power amplifier
02.05.2016
soulution introduced the Model 511 stereo power amplifier. The product is based on four 600VA switching power supplies with improved filtering and six linear, high-speed, low-noise voltage regulators, with a total capacity of storage capacitors of 500000 uF. Current amplification is carried out on three stages, demonstrating increased linearity, the current can reach 60 A. The cutoff frequency is 80 MHz.
The output power per channel when operating at a load of 8, 4 and 2 ohms reaches 150, 300 and 600 watts, respectively, and in mono mode it is already 600, 1200 and 2400 watts. The amplifier is connected to the output terminals with thick copper bars. Power is supplied separately to the amplifying part and auxiliary units, they are isolated from each other by means of optical isolation. The signal-to-noise ratio does not fall below 101 dB, the level of harmonic distortion does not exceed 0,004% in stereo mode, in mono mode it drops to 0,0004%.
The soulution 511 amplifier has one input and output balanced XLR connector and a pair of terminals for acoustics; there is an RJ-45 connector for communication with other soulution components. Those who wish will be able to purchase a novelty in October at a price of about 22200 euros.
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