Sound system mixer gain GAIN setting

All electronic circuits (including the internal circuits of the mixer) will produce low-level electronic noise (or hiss, hum), although careful design can be used to reduce her to the lowest level, but it is impossible Completely disappear (eliminate), but the input signal level will cause distortion of the audio system circuit, so the input level must be set very carefully to get good sound quality (sound quality), the ideal state is of course the higher the input level The better (the higher the input level, the higher the signal-to-noise ratio), but we must save a safe space to avoid the distortion caused by the high-level part, so as not only to ensure that the signal level is large enough to overwhelm and ignore the background noise, but also Keep the signal clear while avoiding distortion. This safe space is called the "allowable range" (headroom) in audio terminology. A good design is to use a very low-noise circuit, but still provide a lot of allowable space to avoid some unpredictable signal peaks caused by peak clipping distortion, PA live performance, the mixer has enough allowable space in the actual The application is very important, because the level of the live signal is unpredictable. Some mixers that are prone to peak clipping increase the risk of damaging the high-frequency driver.

The design of the electric meter is to set the appropriate signal level at 0VU. This arrangement can leave a lot of room to cope with unpredictable signal peaks. To monitor the true peak signal level, please use a peak display type electric meter. Instead of looking at the average value display meter.

 Procedure for setting input gain:

1. Press the PFL button to adjust the channel and monitor it through headphones.

2. Adjust the input gain control knob. Take the human voice without glitch signal as an example, the LED volume indicator (indicator) on the upper right will display at about "0". If it is a snare drum sound, it will be increased to about +8 position, this program must be set repeatedly for each channel before other tasks can be performed.

If the gain setting is too high, the margin is reduced, and the possibility of peak distortion is relatively increased. On the contrary, if the input gain is too small, we will compensate in other parts of the mixer. Necessary noise (hiss).

Please note: the size of the signal through the effector is also adjusted in a proper state. Turn the control knob of the auxiliary output about 3/4, and then adjust the input gain on the effector so that the signal peak is about the 0VU position of the effector itself. Any effect If the amplifier is connected to the insertion point, you must use their own input gain control to adjust the gain to a proper state. If the effector has an input level control, it should be turned to 3/4 at the initial setting.

When the processor is connected to the insertion point of the input channel or the main output channel, if they can be set to work at +4BU (not ?10DBV), they can directly play the appropriate effect without modification, because all the insertion points are at 0DBU works in high level.

Accurate gain adjustment should be a good habit of engineers, and it should also be a routine matter. We spend some time and thought to set it carefully, and we will definitely be able to realize the potential of PA equipment.

Assuming that the sound system is at the 0DB position of the mixer's main output fader, when the sound pressure measured at a distance of 10 meters is 85 decibels, if the volume needs to be adjusted, when the meter does not reach peak distortion, push the fader to At the +5DB position, we can know that the sound pressure at the same position has become 90 decibels. When the push rod is pulled to the ?5DB position, the sound pressure of about 80 decibels can be measured there. With this relative result, we In order to know what we have changed by moving the putter!