I've written two articles about console signal flow logic for this website. The article titled "Signal Flow Simplified" is the abbreviated version of the one you're about to read. I've included that shorter version for people who are beginners in sound as well as for those who don't have a need to actually operate a console and simply want a basic overview. Still, I want people to truly understand this stuff, and I think a thorough, detailed explanation is the shortest route to that end. So if you like to really "dig in" to the topic, or if the shorter discussion of console signal flow logic didn't quite sink in, I think you'll enjoy the following explanation.

Let's take a poll here ­ how many of you use a road map to find the most efficient route to get where you're going? Wow, a couple of guys actually did raise their hand. Well, it may seem odd but one of the best ways to understand how to operate your sound console is to learn its signal flow ­ a simple road map which illustrates how the signal gets from the input to various outputs. I titled this article "Maximizing Your Console" because it's a snappy title that will grab your interest, but now we have to talk about this dry topic of signal flow logic. But please stay with me, because this is truly the secret of achieving confidence in console operation. If you don't have a grasp of signal flow for your console, then probably your approach to operating it is one of "Well, if I twiddle these three knobs just so, push this fader up to here, and never ever let the master fader go past this indelibly engraved red mark that someone has carved into the face of the console, then maybe it'll work today!" There really is a better way, and it's the concept of signal flow logic. So let's get down to work.

Figure One shows the input strip from a hypothetical but typical console. We'll talk about each of those controls as we make our way through the signal flow. On the surface, one might think that the sound flows through each control in sequence from top to bottom. Actually, manufacturers have arranged the controls in a way that they think will be the most efficient way to operate the console. For example, controls that you would for the most part "set and forget" are placed at the top of the input strip, well out of your reach ­ like the Mic Trim for example. Controls that you want immediate and frequent access to are placed right at your fingertips, like the Channel Faders. As we move on to the signal flow diagram in Figure Two, I encourage you to refer back to this drawing from time to time. It will help you relate the signal flow to the related controls.

The signal flow diagram in Figure Two is again from a hypothetical console. This arrangement of the controls is fairly common, and once you understand this concept you can apply this approach to your own console. The diagram reads from left to right, top to bottom. So we start at the upper left corner at the mic input ­ a very good thing to have on a console! The first component that the signal sees is the input transformer. Now, the reality is that on most consoles we work with today, especially on lower cost consoles, the input transformer is actually replaced by a less expensive electronic circuit which accomplishes much the same task. The purpose of this input stage on each channel is to receive the balanced signal from the microphone and to cancel any extraneous noises.

The strength of that mic signal is quite low, and needs to be brought up significantly to operate with a quiet signal-to-noise ratio throughout the rest of the console and beyond. That gain increase is accomplished with the Mic Preamp. Note that there is a related control called the Mic Trim or Mic Gain. This is a gain adjustment for the mic preamp which allows you to adjust for differing signal strengths coming into each channel. I'll explain this in more detail when we discuss how to set the Gain Structure of your console. Your console may or may not have a control labeled Mic Gain. If it does, you know what it is.

 

If you don't see a control labeled Mic Gain, it simply means that the manufacturer has chosen to keep the price of the console down by replacing that variable resistor (called a potentiometer) with a fixed resistor. The manufacturer figures that you're going to plug in mic "A", and mic "B", and you'll place them on these various instruments or voices; then he chooses a ballpark gain setting that should serve your needs for all of the inputs. That fixed resistor costs probably one-tenth of the price of the pot, and when you multiply that times one for each channel on the console, it should lower the manufacturing costs.

The tradeoff is flexibility. For example, you might decide that you get the best sound if you mic a certain instrument in a certain way. If the incoming signal is too hot or too soft, you could use that sensitivity control to adjust for the difference. If you don't have that control, you may have to be a little more creative. For example, what's another way to drop the strength of the signal coming into the console on a particular channel? Well, you could move the mic farther from the instrument.

The main path of the signal goes next to the Equalizer (EQ) section of the channel. This is really just a glorified volume control which allows you to turn the sound up or down in various frequency bands. Your intent should be to improve the tonal quality of a particular voice or instrument. This really isn't the place to talk about equalization, but do remember to be subtle in your EQ adjustments. A small EQ change can make a huge improvement in the quality of a person's voice. But there are times when you won't need to alter the EQ. Part of your job as the engineer is to know the difference, and then to not twiddle the EQ knobs just because they're there.

The signal then flows on to the Channel Fader. Fader is the hip term. And I want all my readers to be hip, so you can stop using the term "slider" and replace it with "fader" when you're talking about consoles. Here's where most of the action of your mix happens. The fader is where you want to make adjustments in the balance of each voice or instrument during the song or sketch. Faders generally have a logarithmic taper. That is to say, the rate that the volume changes will vary along the throw of the fader. For example, a 1/4" move of the fader near the top of its travel may account for a 5 dB change in level, whereas the same 1/4" move of the fader near the bottom of its travel may account for a 20 dB change in level. Because of that, your mix will be smoother and quieter if you operate the faders in the upper one-third of their travel for the most part. This again deals with gain structure, and I'm just about to that point.

Now you'll find our signal path at the summing point. The Greek Sigma symbol with a circle around it is a common notation for a "summing" or "combining" point. The signal flow diagram you've been working with here shows just one channel of the console, but let's say that we have been talking about a sixteen channel console. Each channel is identical up to this point, and then they all combine or sum at this point.

The signal then goes to the Master Fader where we control the overall level of all the signals with one fader. The signal then goes through the output stage of the console circuitry, and then to a connector on the back of the console where we plug in a cable and feed the signal out to the input of our power amplifier, for example.

That's the main path through any console. No matter how expensive, that's it. But we still need some more information on how the controls interrelate, so look back at the signal flow diagram and note that right after the mic preamp and before the EQ there is a pickoff point. You could think of it as a side road on your map. The path drops down to a control I've labeled Auxiliary #1, and if you'll follow the signal path down, you'll see that it comes in contact with the Aux #1 Buss. This is basically a piece of wire that runs from one side of the console to the other. The signal then flows on to the right to the Aux #1 master control, which controls the overall level of all the signals fed to the Aux #1 Buss.

Let's imagine for a moment that we're using Auxiliary #1 to feed a set of stage monitors. We're looking at channel #5 which is the lead vocal mic, and Aux #1 feeds the lead vocalist's stage monitors. If you were to make an adjustment to the EQ on channel 5, would that change be heard in the vocalist's monitor mix? No, because the feed for the monitor mix is picked off before the EQ. If you make an adjustment to the lead vocalist's channel fader, would that change be heard in the vocal monitors? No. We're using what is known as a "prefade" auxiliary send, because the signal is picked off before the fader. It also happens that the signal is picked off before the EQ as well, but the proper term is "prefade". What about if I make a change to the mic trim on channel 5? Yes, since it's upstream in the main path, changing the setting of the mic trim would affect the signal to both the main path and the auxiliary send.

While we're on the topic, this relationship is usually the preferred setup for mixing monitors. Most vocalists and musicians would prefer that, once their monitor mix has been established during soundcheck and rehearsal, that their mix not change during the course of the worship set unless they specifically request it. Unexpected changes in the mix can be very distracting to the worship team, and while they're up there trying to lead others into worship of the God of the Universe, they just don't need that distraction. No pressure.

Just past the fader is another pickoff point that goes to a control labeled Auxiliary #2. As before, this also drops down to an Aux #2 Buss and its related master control. In this case, let's imagine that the Aux #2 output on the back of the console is patched to the input of a reverb unit sitting in an equipment rack next to the console. In order to hear the reverb, the output of the reverb device is connected to a line level input on the console called the Auxiliary Return. We establish our dry-to-wet ratio by adjusting the send on Aux #2 of channel 5, and of course the return level of the reverb unit is adjusted with the Aux Return. The "dry" sound is the direct signal from, in this case, the vocal mic, and the "wet" sound is the reverb effect.

Now that our reverb sounds the way we want it to, if you make an adjustment to the lead vocal fader, does that affect the signal fed to your reverb device? Yes, of course it does. What if you make a change to the EQ on channel 5? Yes, we'll also hear that change reflected in the reverb sound. Does adjusting the master fader affect the feed to the reverb device? No, because the feed to Aux #2 is picked off before the master fader. What if you change the Aux #1 send on channel 5, will that affect the signal fed to the reverb unit? No. Even though Aux #1 is picked off upstream from the Aux #2 feed, it is still just a pickoff point. It will not affect the main signal path. I'm sure you can now realize that the Aux #2 send described here is commonly called a "post-fade" send.

It is typical to use a post-fade send to feed effects devices because doing so allows us to easily maintain that dry-to-wet ratio. It is generally a more musical sound for the loudness of the reverb to track with the direct sound. If you push the fader up, the direct sound increases as does the feed to the reverb unit, so the dry-to-wet ratio is maintained. If you pull the fader down, the reverb sound diminishes as well.

By now you should see the value of understanding the signal flow logic of any console, especially yours. Its the simplest, most efficient way of understanding how the controls on a console interact.

So do you want to have absolute confidence in operating your console? Do you want to be able to walk up to any console, even one you've never seen before, and within moments understand clearly how to operate it properly? Then here's a challenge for you. Study the signal flow diagram for the console you work with. The owner's manual for your console will have a block diagram of that console. Those signal flow drawings are often awkward to read, so redraw it! That's right, redraw it so it looks more like the drawing in this article. Not only will it be easier to read and simpler to understand, but you'll also start reinforcing your understanding of its flow. Redrawing it forces you to pick apart the signal flow and understand how the controls interrelate.

Get to the point that you can take out a blank sheet of paper and a pencil and draw the signal flow of your console from scratch. I promise you that the day you achieve that task will mark a new era in your work as a sound engineer. From that day on you will operate your console ­ or any console you walk up to ­ with confidence. Your mix will be consistent from week to week. You'll be past the point of the console operating you. Then the Holy Spirit can work through you. I found out long ago that the times I allow God to mix are the best. He mixes way better than I do! You'll notice a problem with feedback and your hand will dart the appropriate knob to resolve the problem, and you won't even know why. This is way cool.

Your renewed confidence will extend to new consoles that you come in contact with, and you'll find that within moments you'll have the same sense of confidence with a new console that you enjoy with the one you've been working with for some time. All you have to do is get past the silkscreen of the new console's manufacturer. For example, what one manufacturer calls "solo" another labels the same control "cue", and still another labels it "PFL"; what one manufacturer calls "monitor send" another labels "foldback". It doesn't matter if the console you're used to cost just $600, and the new one you're facing cost $60,000. The reality is that they both possess the same basic signal flow. The cost increase is reflected in flexibility of signal routing, quality of the internal components, and circuit design improvements.