Microacoustic preamplifier of general use
This microacoustic preamplifier is able to amplify the signal of exit of a dynamic microphone until a level of 0.5 to 1 V. The frequency response is of 20 to 35000 Hertz.
The circuit consists of a two-stage amplifier with direct coupling, that becomes stabilized by means of the use of CC. refeeding The same works very well with dynamic microphones whose impedance oscillates between 200 and 30000 ohms.
This preamplifier is designed to work with a source of tension from 18 to 20 V, if ohms by each volt is desired can be used a source of greater voltage increasing R8 400 that surpasses the 20 V.
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List of Components
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Resistance: (0.5 W, 10%) |
Capacitores |
Semiconductors |
| - R1 - 220 ohms for microphone of low impedance; 270 K for microphone of high impedance - R2 - 10 K ohms - R3 - 27 K ohms - R4 - 100 ohms - R5 - 120 K ohms - R6 - 3900 ohms - R7 - 680 ohms - R8 - 1500 ohms |
- C1 - 25 uF, 6V, electrolytic. - C2 - 300 uF, 6V, electrolytic. - C3 - 100 uF, 25V, electrolytic. - C4 - 20 uF, 25V, electrolytic |
- Q1 and Q2 - Transistors RCA SK3020 |
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