If you are new to the world of recording or live sound, using a mixer can be a tricky thing. This article will explain the basics of how just about all mixers work so you don't have to figure out these concepts the hard way...like I did.

Preamp / Trim

At the top of just about every mixer I've ever used is a little knob for each channel. This knob is what I, as a recording dude, call a preamp. Some guys call these knobs “trim”. The purpose for this knob is to boost the signal up from mic level to line level (which is what mixers, compressors, sound cards, etc all need to function).

The idea is to use a preamp to boost the signal up to a level you can work with. You should have a healthy amount of signal, but you do not want to clip or overload the input as this is distorting the signal which sounds terrible and can damage equipment.

Inserts

The insert acts like a break between the preamp and the rest of the mixer. This is a spot you can tap into that will allow you to place compressors, external equalizers, etc on a channel. Typically speaking, inserts are used with gain based effects mentioned above (eq, compression, etc). They are generally not used for time based effects (delay, reverb, etc).

In the recording world, external mic pres are quite common. It's easy to connect a mic preamp to an external compressor because you have clear access to the output of that preamp and you can decide to send the preamp to a compressor, eq, or directly to a sound card if you choose. Since it's not nearly as simple to get to the outputs of the mic pres in your mixer, they've added the insert jacks to give you access to the output of your pres.

Note: If you already have a mixer and are looking to get into recording, a popular trick is to tap into the inserts and send that signal straight to your sound card. For years, I used my Mackie mixer on most of my drum tracks and I kept cables plugged halfway into the inserts. This let me split the signal to my soundcard right after the preamp, but also retain full control of my mixer for headphone mixes or whatever else I'd use my Mackie for.

Auxiliary Sends

Auxiliary sends are often called aux sends. The purpose of the aux sends is to let you send the signal from that particular channel anywhere you want to. So let's say you've got a vocal track. Where do you want to send it? We can send it anywhere we want to. I can send it to a reverb, a delay, chorus, more compression if I want, or even a guitar amp (for crazy effects). For monitoring, I can send the vocal to a set of floor monitors (like on stage) or into the input of a headphone amplifier.

Keep in mind, that we have only sent the signal out of the mixer. We'll need to bring it back into the mixer if you want to hear the newly effected signal. (Of course, this doesn't apply with monitoring). So if you want to hear that reverb, you need to send the outputs of that reverb back to the mixer. You can plug the reverb unit's output straight into a channel of a mixer. This is how a lot of mixers function. You can also send that reverb output into a special effects return. Not all mixers have this, but most modern mixers do.

This gives you control over the level of the effects coming back.

Equalizers

Even the cheapest mixers have Eqs (if of limited used). In the budget mixers, EQ is typically fixed at a certain frequency. This means that when you boost or cut the low end you are also going to be manipulating the frequency set by the designer of the mixer. An EQ set at 85Hz is not going to help much when you only want to cut a little 150Hz.

In a live sound situation, I find these fixed-band types of equalizers to be almost completely useless you have at least 15 bands (31 is even better).. The whole point of an EQ is to overcome problems with how the PA system interacts with the room. If we are too boomy, we use the EQ to “equal out” the boom. If you can't cut or boost the frequencies you'd like to cut or boost, the EQ is useless.

Some mid priced mixers come with a sweep filter. A sweep is awesome because it lets you change the frequencies you are manipulating. Let's just say that our low band is fixed at 100Hz, but we are getting some feedback at 200Hz. A fixed EQ can do nothing to help the problem. However, using a sweep, we can change the frequency from 100Hz up to 200Hz and then cut maybe a few dB. This is a semi-parametric EQ. A fully parametric EQ gives you control over the bandwidth (how wide the dip or boost is).

In a modern home recording studio situation, there is no need to use the equalizer on a cheap mixer. Audio recording software almost always comes with equalizers built in that will give you far more control over your tracks. This is just another reason that the mixer is not necessary in a home recording rig 99% of the time for 99% of the people.

I'm also against using equalizers when tracking in general. There are exceptions, but most of the time, a beginner will go nuts on eq that can not be taken off without artifacts. While after 5 years of recording, I could probably do well with an EQ while tracking, I've learned when to use it and when not to use it. If you are just getting started, stick to using the EQ on your recording software.

Low Cut

Many mixers have a low cut switch around the EQ region. This is not a complex concept. You push the button and the deep, subwoofer bass for that particular channel is gone. I wouldn't use it on a kick drum, bass guitar, or floor tom as these have low end in them. However, I can't think of a time where I would want deep bass in the vocal mic, guitar mics, etc.

Panning

In the live sound world, panning lets you decide if you want an instrument on the left or right side or somewhere in the middle. Panning is a fairly straightforward concept and usually doesn't require much explanation.

If you are recording mono tracks from your mixer, than the panning knob is useless. Why? Because your tracks are mono. You can always pan them when you get into your recording software. So if you are recording mono tracks, you may just want to keep the pan centered. Of course, if you are tapping off the inserts (as mentioned above), the panning knob won't do anything because you are bypassing everything after the preamp.

Volume Faders

The volume faders are usually pretty self explanatory. Pushing them up makes the sound louder. Pulling them down makes the sound quieter.

Most people have problems with their volume because they didn't set their preamp correctly. If you do not boost enough with your preamp, you will find yourself making up for it with the volume faders. The volume faders typically don't allow you to boost the signal by more the 6dB or so depending on your board.

So then, the beginner will reach for the preamp and boost it. However, there is only one problem with this. You have boosted the signal everywhere. You've boosted it in the main mix (which you wanted) but you have also boosted it in the monitor mixes, reverb sends, etc. So make sure you get as much level without clipping on your mic pres first.

If you are using a mixer to submix drums. (Maybe you don't have enough inputs on your soundcard to record each mic to its own track). People on tiny budgets tend to recording drums in this fashion. It's not ideal, but you can make it work. In this case, I'd be very careful when using a cheap mixer when it comes to my preamp levels. There is a point where noise kicks in on cheap and even mid priced mixer mic pres. There is a point not long after that where the noise increases exponentially. It's generally better for me to keep the pres down just a tad and avoid the noise. For recording, you can always boost the signal a little bit in the recording software. (Note: It's preferred to use a preamp to boost the signal, but if it comes down to adding noise or boosting within the recording software, I'll choose the recording software everytime).

Busses

Not all mixes have busses, but even some low budget mixers have a few. It's great having total control over where your signals are going. You can assign a channel to a bus (which is a way of submixing as many channels you want into another fader before the signal hits the master fader.

Let's say we have 10 drum channels on our mixer (and presumably 10 channels of bass, vocals, guitars, keyboards, etc).. I want to put them all 10 drum channels on the drum buss (which is Bus #1 ). This lets me control the volume of the entire drum submix with just a single fader So if the drums are well balanced but too loud, I simply pull that one bus down. It's quicker, but it also gives more processing options. Let's say we want to compress the drums as an entire unit. You can add a compressor on that bus. I can do the same with EQ or any other processing.

Here's a trick I used to do with routing.

When recording a vocal overdub, I'd have the singer in the other room with headphones. I'd give them a mix with aux sends. This means that I'd send a stereo out of my recording software into channels 1 and 2 of my mixer. Then I'd put the vocal on channel #3. I'd use the aux sends to feed a headphone amp. If the singer wanted more vocal in his headphone mix, I'd reach for Aux #1 on Channel #3 and boost it.

Okay that's normal.

From there, I would assign the music directly to the master fader (no busses). Then I would assign the vocal to Bus 1 (which after passing through the Bus 1 volume fader and possibly effects then went to the master fader). This gave me a totally different volume control for the vocal in the control room vs the singer's headphones.

If I wanted to, I could mute the singer in the control room, but keep the music going if I wanted to.

Note: There are easier ways to do this little trick, but it does illustrate possibilities you can do with creative routing.

Conclusion

These are the very basics of getting started with your standard analog mixer. Again, I want to repeat that there are few cases anymore where I find a small analog mixer to be useful for recording. Most computer interfaces combined with high quality recording software can do everything and do not need help from a mixer.

If there is anything I left out, please let me know.

If you have any questions, feel free to ask on the forum.

Brandon