Keywords: noise suppression circuit
The sound enthusiasts should want to get high quality playback effects, in addition to high-fidelity audio equipment, try to effectively suppress noise in the sound source itself. I have made a dynamic stunning suppressor for multiple trials, which makes tape, record, and radio suggestions such as sound sources.
The principle of the circuit is shown below. The output signal is divided into two channels, all the way to R3, C6 to the output. V2 is a numeral field effect tube, which is used in circuitry, and its source voltage is determined by the voltage ratio of R5 and R6. The C5 is the bypass capacitor, and the fine-tuning W2 is used to adjust the V2 gate voltage, which makes it slightly reflected in signalless output. At this time, the source of the drain is about 100 Ω, and the resistance is small, and it is C4. AC channel is provided via the V2 drain source and provides an alternating channel through C5. The C4 is then formed together with R3, which is attenuated to noise (mainly in the high tone band) in the output signal of the C6.
Another input signal is input to the base of V1 by C1, and operates in the common emitter amplification state, and the static bias is determined by R1. R2 is the collector load resistance of V1, W1 is the emitter resistance of V1, is used to change the negative refrigeration amount of the amplifier, and the control gain. The output of V1 is conveyed by C2 to a rectifying circuit composed of D1, D2, and the rectifier output is connected to the V2 gate, and its output voltage controls the magnitude of the high frequency filter circuit channel impedance.
When the weak signal is input, the rectifier circuit output is small, and the V2 does not affect, the noise of the input signal is filtered out of the C4, R3 network. When the input signal level becomes large, the rectifier output is increased, causing the V2 gate potential to reduce the C4, R3 filter channel, which reduces the amount of attenuation of the noise, and the attenuation of the high audio component is also reduced. If the rectifier output is large, V2 will be cut off, the filter channel is completely cut, and the output signal is not affected by the filter circuit. In summary, the noise suppression circuit has no effect on low, medium and audio signals, and higher levels of high-tone signals, while only high frequency components in the weak signal are inhibiting noise, and there is a degree of attenuation.
C3 is a filter capacitor to stabilize the output voltage of the rectifier circuit, preventing the V2 gate from being affected by the pulse, suddenly decreased, causing signal distortion. The C3 capacity should not be too large, otherwise the upper voltage will not be able to change the input signal level. C1, C2 is a coupling capacitance, in order to increase the response speed of the amplifier to the high audio signal, their capacity is smaller. The action level of the noise control circuit is controlled by W1, and when the boom is at the upper end, the action level Du minimize the minimum.
This circuit does not have special requirements for components, and V1 β value should be ≥70. When actually used, the inhibitor input end is connected to the source of the sound source. The best position of W1 can be repeatedly adjusted, determine the best position, then fine adjust W2, and make the best time.
This syntine controller applies in the old Chinese brand recorder to drive the electronic management power. If the stereo source, you can make a photo. Author: 福 福
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