The Adjustment of Amplifier Volume

- Jul 11, 2018-

When we are tuning, first adjust the gain control button of the input channel of the mixer. When the signal is input to normal input, the peak indicator of the channel will occasionally flash, but it will not flash frequently. The purpose is to make full use of the amplification of the amplifier of the front stage effect.

   In theory, the preamplifier has a large magnification, which is beneficial to the improvement of the signal-to-noise ratio. The faders of each input channel are generally adjusted to between -3dB and 0dB, instead of adjusting the faders of the input channels. Similarly, the same is true for the adjustment methods of the output faders and the main output faders. In principle, the output levels of each channel are generally around 0 dB. The same applies to the regulation principle of each peripheral device.

   Therefore, under normal circumstances, the power amplifier's volume control knob will not be at the maximum position, specifically, the sound pressure level of each speaker is adjusted to the desired sound pressure level. Some power amplifiers have low input sensitivity and have a nominal input level of +3dB or +4dB at rated output. At this point, the 0dB input will not allow the power amplifier to reach the rated output. In fact, the rated input and rated output of the power amplifier refer to the rms value of the sine wave. The crest factor is 1.414, and the program signal we play is not a sine wave. For high-fidelity sound reinforcement, the crest factor should be guaranteed 4, therefore, the rms level of the program signal should be much lower than the rated input level of the power amplifier and should be less than or equal to 1/2.83 of the nominal input level.

   In the electrical schematic, the volume control of the power amplifier (ie, the volume potentiometer) is typically at the input of the power amplifier circuit, ie in front of the voltage amplification stage. The volume potentiometer adjusts the magnitude of the signal voltage applied to the voltage amplification stage. That is, the volume potentiometer functions to apply a portion of the signal voltage applied to the input of the power amplifier to the voltage amplification stage of the power amplifier. In other words, for a specific power amplifier, the voltage amplification factor is a fixed value, and the volume potentiometer does not change the amplification factor of the power amplifier, and only changes the signal voltage actually applied to the amplification circuit.

   Because of this, you don't have to pursue the power amplifier's volume button to the maximum position. As you said, when the volume button is turned to the maximum, it may bring side effects. Once an abnormal large shock signal arrives, the shock signal will be added to the amplifier circuit of the power amplifier because the volume button is at the maximum position. This produces a very strong shock signal that is applied to the speaker, causing damage to the speaker.



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