Now that we are back to audio channels, see the examples below. Remember, that the channels run down from the TOP. In some mixing boards, there is a ‘pad‘ switch – it could be above or below the 1st gain knob – that can determine which input type will be monitored by that channel and it can also change the input level or signal strength. To reinforce the general definition below, if the audio source uses a battery or gets plugged into AC, it will need to be ‘padded‘ using this switch, where MOST microphone applications will not be strong enough if the channel is padded.
Whatever is plugged into the input jack on the mixer for that channel will send a signal to the 1st ‘gain stage‘.
This acts more like a flood gate than an amplifier in that it allows you to reduce the strength of the signal coming into that channel. But it feels like an amplifier as when you turn it clock wise – it gets louder and if you turn it counter-clockwise – it gets softer or lower in volume…… This is the great balancer. This knob determines how much of the signal gets distributed or sent to other out puts, effects, processors and recording devices, etc. This is the foundation of the mix you are creating. We start here and do not continue with the other knobs and gizmos in the ‘channel strip‘ until this is set correctly.
The biggest trick in setting this up for most band performances is – well – band members. A lot of them do not trust the sound guys they have worked with for a lot of reasons. Some performers will set their level (amp, energy, settings) really low during sound check, knowing once the sound is going they can turn themselves up so they can hear themselves. Most often, it is just difficult to play really hard and loud like you will during a full band live performance when no one else is making noise. Knowing all that, you need to start with a good level here so you can set the gain stage properly. Generally, open microphones will need more gain than instruments like keyboards or mp3 players. Things that get plugged into AC or use a battery will probably have a stronger signal strength than those that go directly to the snake/mixing board.
As a caution again, make sure the amplifiers are turned all the way down before you plug anything into the mixer once the full system is connected. We tested the House PA and Stage monitors before the band got here, so before you start plugging in instruments and performers, turn the House PA amplifiers down. I also turn the Monitor Sends down all the way so you do not hit the monitors with some pretty ugly sounds. If you use fantom power for your microphones or other devices, I have heard people suggest you do the same whenever turning this function ON or OFF.
Now we are ready to move through the rest of the channel. I am old school, and I like to start with the mixing board ‘clean’. With all knobs and gizmos set to center or neutral. Some guys like to start off where they left or pre-mix, but I have seen many situations where that theory gets yanked.
Above board design has the +48 fantom power switch. When pressed in it will send appropriate voltage to the microphone or device. Best to have Master faders turned down during this part as well. Underneath is the pad/Line switch. This you can safely determine a good guess in advance depending on what type of instrument is plugged into that channel. You can always start with pad pressed in and gain stage at minimum to be on the cautious side and then release pad and turn gain knob as you watch the signal LED’s. Get good performing signal as opposed to good practice level and see where the gain stage knob is pointing. Try to get signal meters and LED’s close to the red or overload stage, and then back off the gain stage knob just a little. We may need the extra head room when we add EQ, use ‘inserts‘ etc.
This board and many others offer a HPF (‘High Pass Filter‘). When depressed it will allow mid and high frequencies to go through the channel and process normally. So, it really cuts or turns down the really low end signals. This is where the frequencies and ranges of instruments in an earlier LSR series come into play. Instruments like, flutes, acoustic guitars, vocalists, cymbals, snares cannot make sounds in the low end. The over-all mix will benefit if you use the HPF and cut the very low frequencies on those instruments. Microphone stand rumble, bleed over from the kick drum into the snare along with a number of other unwanted sounds can be eliminated before they even get into the mix.
Next series we will continue down the signal path.
MidiMike 