This microphone compressor circuit utilizes a two-stage amplification design for dynamic range control. Initially, the input signal enters through MK1, a microphone input connector. Subsequently, the signal passes through C1 and C3 coupling capacitors for DC blocking.
The first amplification stage employs Q1, a 2N3904 transistor configured as a common emitter amplifier. Meanwhile, R1 provides bias stabilization, while R3 sets the collector load impedance. Furthermore, C2 serves as a bypass capacitor for improved frequency response.
Next, the signal proceeds to the second stage featuring Q2, another 2N3904 transistor. Additionally, this stage incorporates automatic gain control through the feedback network. Specifically, VR1 and VR2 form a voltage divider that controls compression characteristics.
The compression circuit monitors output levels through R2 and adjusts gain accordingly. Consequently, loud signals experience reduced amplification, while quiet signals maintain normal gain. Moreover, C4 and C5 provide frequency compensation and stability.
Finally, the compressed audio signal exits through the AF OUT connector. The power supply connects to +9V, while C10 provides power supply filtering. Overall, this circuit effectively reduces dynamic range variations in microphone signals, making it suitable for audio recording applications.
Gerber file – Download
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