Recording Studio

What do the knobs on the mixer do?

Take the part outlined by the red line in the figure for example. In fact, the frame is quite interesting, basically frame the important parts of a “channel strip”. But there are a few less that haven’t been photographed — those aren’t knobs. The missing “not knob” parts are above and below the box. The top is the 6.5mm “big three-core” interface, and the bottom is the “fader” that can slide up and down. There may also be an empty box above the fader for someone to write or label to annotate what signal the track is. These strings together make a complete “channel strip”. An input channel strip, to be precise.

I will try to speak from top to bottom.

Let’s talk about the interface first. The analog signal is input from the 6.5mm interface. For example, this is an electric guitar.

After the signal comes in, it first goes through the red gain knob to amplify the signal. Generally speaking, the left limit of the gain knob is 0dB, which means that the input signal is not amplified. The right limit is generally greater than 30dB or 45dB, and some consoles may exceed 65dB (the number may be wrong), because if the sound is from the microphone When it comes in, the level is often relatively small, and it needs to be amplified enough to make people hear it clearly; the output signal of high-level instruments such as electric guitars, electric basses, electric pianos, etc. may already have a large enough level, and often do not need The mixer is amplifying too many times, and even needs attenuation. For example, in the picture, if you look carefully, there are two scales below the red knob, which are -35db ~ +15dB: Line and 0dB ~ +50dB Mic. They correspond to the two situations I mentioned.

There is also a small green light next to the red knob, which is the signal level indicator. Generally speaking, if the light is off, it means that the signal is too weak, or there is no signal input. Green means the signal strength is healthy and appropriate, yellow means high-energy warning, and red means the signal is too strong and clipping has occurred.

Next is the blue part, equalizer, eq, equalizer, generally speaking, it is to adjust and modify the sound. The one in the picture is the equalizer that a typical analog mixer will be equipped with. This is a high-mid-low three-band equalizer. The Q value (that is, the wide and narrow range of the frequency band) is often fixed (not marked, which means that you can feel it), and the frequencies of high and low frequencies are also fixed at 12kHz and 80Hz, respectively. , the gain range is -15dB ~ +15dB. The mid frequency is 2.5k Hz by default, but it can also be manually adjusted in the range of 100Hz ~ 8kHz.

Note that in the middle of the red gain and blue EQ, there is also a small black button, which is a low cut switch, which is preset at 75Hz, and the “slope” is 18dB/oct, which is a decent slope.

Below the blue EQ, there are four yellow knobs, divided into two parts, two auxiliary send AUX knobs, and two effect DFX knobs. In fact, the knob here is equivalent to the fader. It’s just the physical size limitation of the mixer, which is made into a knob. Each “fader” has a range from minus infinity to +15dB. There is also a small black button between the upper and lower sets of yellow knobs to switch the pre-fader/post-fader, that is, to adjust whether the effect we set in the yellow area is applied before or after the fader. What does it mean? I’ll talk about it later.

There is one left under the yellow knob, and the black knob, PAN, is generally called pan, which simply adjusts the left and right position of the sound. Because the final output device is stereo and the input signal is mono, the pan can adjust where the sound of this track is placed from the far left to the far right. From another perspective, our speakers are a pair, left and right. The listener has two ears, and the singer has only one mouth. This pan is to adjust the ratio of the output volume of the song in the left and right speakers. , is the same size, or which side is biased.

It’s not over yet, look at the photo carefully, there is a red light below the pan, and a square button that is only half-shot, I guess it should be the mute switch mute, that is, “one-click to shut up”.

Generally, there will be solo switch buttons in software mixers and digital mixers, but it is not common in analog consoles.

Further down is the fader that has not been photographed and can slide up and down. Generally, the range is from negative infinity to +12dB. This is what we all say, “Push the volume up!”

Then I’m going to go back to the pre- and post-fader buttons that I just skipped over in the aux section. why? Because if you don’t say that, it will be more difficult for you to understand. What is it good for?

for example. Generally, when tuning, the fader is at 0dB as the reference first. All gain and output volume must be matched with the fader. For example, in such a large venue and so many audiences, I strive to make the track when performing. The faders are all around 0dB, so that everyone can hear it clearly without feeling that the volume is too loud or too low, which is just right. If the gain is reasonable, the total fader is at 0, or even more than 0 is pushed to the top, and it is +12dB, and the volume is still not enough, it means that the venue is too large, the power of the speakers is too small, and it can’t hold the venue.

OK, back to before and after the fader. Assuming that the venue and volume are suitable, and the fader is near 0, you want to sing a song, but you can’t sing it dry. You need to add some reverb effects. This reverb is usually sent through the aux auxiliary send, or the built-in effect channel of the mixer. arranged. Let’s assume that the Aux 1 channel is the reverb we set up, the track fader is at 0, the aux knob is at -15dB, and the volume ratio at this time is just right for us. So what’s the difference between switching pre/post fader?

If the aux is set after the fader, the volume of the reverb will be affected by the channel fader. If we push the fader up or down, the volume of the singing voice will become larger and smaller, and the reverb will follow accordingly. It becomes larger and smaller, but basically maintains the volume ratio set before based on 0dB.

If the aux is set before the fader, the reverb volume will not be affected by the fader, and will not follow the fader change. If the fader is pushed up at this time, the singing voice will become louder, but the reverberation will remain unchanged. Correspondingly, the reverb The ratio will become smaller; if you pull the small fader, for example, to -50dB, the singing itself will be very small, but the reverberation will remain at the previously set level, and what you hear at this time is basically the reverberation, not the direct singing. This is a use case for pre/post faders.