Compressor Audio

Automatic Gain Control or AGC is a circuit design which maintain the same level of amplification for sound or radio frequency. If the signal is too low the AGC circuit will increase (amplify) the level and if is to high will lower it to maintain a constant level as possible. The Automatic Gain Control principle is widely use in AM receivers and sometimes AGC is called an compressor-expander because it acts just like one.

On the electroschematics.com site you can find some AGC schematics, just use the seach box.

Mic preamplifier with AGC schematic

This audio compander circuit schematic is equiped with NE575 produced by Signetics, it is working with a 3 – 7V battery and has a current consumption of 3.5mA at 3V and 5mA at 7V. The companding process ( input compression, output as expander) is improving the signal/noise ratio on a communication line.

NE575 contains 2 ic’s , pins 1 to 9 works as expander and the 11 to 19 pins can work as expander or compressor or automatic load control ( ALC ).
NE575 has a a high input sensitivity, the maximum input level is 1.5Vef. Thiscompander covers a frequency domain from 20Hz to 20KHz, the total distorsions are below 1% and the signal/noise ratio is 80dB.

Compander circuit schematic

This is a dynamic audio compressor which outputs a constant audio level and can be used for FM transmitters too. It uses a preamplifier with TDA 1054 produced by SGS-ATES. IC1a is a preamplifier stage with a total gain of 50 (1 + R5/R4). IC1b is connected as a amplifier stage with a 400x gain (1 + R11/R10).
The audio compressor power supply has 9V.

Schematic of DIY Audio Compressor Circuit

This mini audio compressor circuit use only one active component T1. The audio signal goes thru C1, R1, D1, C2, R3. Still a part of audio signal charge the D3/D4 detector and creates a control voltage for T1.
The fading time depends on C4 and R5. With an audio input variation of 50dB, the output signal get is +-3dB. You can use this audio compressor circuit in a transmitter.

Schematic of Audio Compressor Circuit

dynaaudiocompressor: 

In many audio applications, regulating the audio signal to a constant level is very important. This is true specially for voice modulated radio transmissions. Voice regulation is also often applied in intercom devices or telephone systems. Such a voice level regulator need not be very expensive.

The circuit featured here combines simple design with inexpensive materials. This simple audio compressor uses a straightforward regulation technique to constantly control the amplitude of the output signal. In contrast to common feedback techniques where the output is used to regulate the input signal, the output signal of this circuit is being regulated by the input signal.

This technique simplifies the overall design of the circuit. Surprisingly, the transistor T2 works as the only active component in the circuit.

This compressor functions very well in intercom systems or in radio transceivers. It can also be used in PA systems or telephone devices such as automatic answering machine.

Printed Circuit Layout

link : http://www.electroschematics.com/tag/audio-compressor-circuits/








Daftar komponen:
 Resistor
 R1 82k
 R2 4m7
 R3 470k
 R4 2k4
 R5 470k
 R6 390k
 R7 470k
 R8 6k8
 R9 220k
 R10 100k
 R11 1k5
 R12 10k
 
 Capasitor:
 C1 47n
 C2 47n
 C3 2n2
 C4 4u7
 C5 4u7
 C6 4u7
 C7 4u7
 C8 2u2
 C9 4u7
 C10 47p
 C11 680p
 C12 10n
 
 Potensio:
 LEVEL 10k
 GAIN 10k
 BIAS 10k
 BRIGHT 10k
 
 Dioda:
 D1 1N4148
 IC1 4558
 J1 Jumper
 J2 Jumper
 J3 Jumper
 Fet:
 Q1 2N5457
 Q2 2N5457

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