Posts Tagged 'board'

Mic’ing Guitar Amps

First, identify the location of the speakers in the cabinet. Don’t assume that the speaker location is symmetrical (some are, some aren’t.) You may have to look inside the back of the cabinet if you can’t see through the front grillcloth.

You may need to look at the back of the cabinet or shine a flashlight through the grillcloth to locate the position of the drivers inside the cabinet.

Next, aim for the center of the paper cone, and about 1-2” from the grillcloth. This is the general starting place for all setups. Adjustments will be made from this baseline, based on the sound desired and/or to fix problems.

WHICH MIC? There are quite a few choices these days. The baseline microphone for guitar amps is the Shure SM57. It will almost always work.

Shure SM-57

Working from the 57 as a baseline, there are some other choices such as the Beta 57, Audix i5, and the Sennheiser e609. The Audix i5 has a more pronounced proximity effect, which might give you more low end if close-mic’d. The Sennheiser e609 goes the other way, offering a less pronounced proximity effect if the amp is pretty bass-heavy already. Beyond that, you have the more exotic and expensive choices of large diaphragm condensers and ribbon mics.

New options: The Shure Beta 57, Audix i5, and Sennheiser e609.

TONE TIPS: There are two ways to get more low frequency response. (1) move the microphone closer to the grillcloth and take advantage of proximity effect, or (2) move the microphone more to the outside of the paper cone area. These tips also work in reverse for more brightness. You can also try angling the mic to see if the off-axis response might work to your favor. It’s always better to try moving the mic rather than reaching for EQ though. Moving the mic a couple inches might dramatically change the sound, and still leave you some EQ options.

A pedalboard help's today's guitarists achieve a wide variety of sounds.

PHILOSOPHY: We always start from the assumption that the musician knows their gear, knows what sound they are trying to achieve, and has adjusted their pedals, tone knobs, and gain structure to produce the sound they want. So the primary goal here is to faithfully reproduce the sound that is coming out of the amplifier. Match tone first. Then improve if it needs it. Don’t just hang out in the booth during rehearsal. See what it sounds like coming out of the amp so you know what it should sound like coming out of the house.

WHAT IF THE TONE STILL STINKS? Sometimes, especially with newer players who do not know their gear very well, you have the situation where the sound coming out of the amp is just not good. If, regardless of mic choice, mic placement, and tone adjustments in the booth, the electric guitar sound is still unusable in your opinion, then it is time to talk to the stage. The first thing to do is to confer with the Music Director, Road Mgr, or Band Leader. DO NOT APPROACH THE MUSICIAN DIRECTLY UNLESS YOU HAVE A GOOD PERSONAL FRIENDSHIP WITH THEM. Calmly explain the problem. Let the Music Director, Band Leader, or Road Manager make the call.

WHAT ABOUT VOLUME? If the stage volume is out of control, the first thing to determine with a player’s rig is if they are using the speaker cabinet as a monitor or as a tone-generator. For example, if they use a Line 6 Pod or other tone modeling device to achieve their sound, then the amp could just be used as a simple monitor, and lowering the volume will make everyone happy. However, if they are using the tubes in the amp to achieve the desired tone, then it may be a tough sell asking them to lower the volume. If that’s the situation, then you have to look at (1) changing the direction of the amp, (2) changing the location of the amp, (3) changing to a smaller amp, (4) utilizing one of the many “power attenuator” type devices on the market (such as the THD Hot Plate) to lower the cabinet volume, or (5) building an iso-box for the amp.

A look inside an iso box at Buckhead Church.

BONUS: How to build a isolation box to eliminate stage volume. (source: Buckhead Church’s production people.)


First Things First

(an excerpt from the SoundSessions training course)

Being part of an audio team is a special privilege. We have the ability to affect everybody’s experience for the good or bad. We can really set up the people on the platform to win , or we can be an obstacle to their success. We have a high responsibility and the people on the platform are putting their trust in us that their artistic endeavors will arrive at the audience’s ears with a true representation – without us imposing our own preferences and biases.

We have two tasks that are equal in priority:
Provide a H O U S E  M I X that is representative of what’s happening on stage.
S E R V E the people on the platform so that they can do their best.

Pleasing other people can be important, but it cannot take precedence over the above goals. You have to know who it is you work for. Making the lead singer’s mother happy is not a consideration. Taking volume advice from the loud drunk at the festival or the cranky church Deacon is not recommended. But neither should we go to the other extreme and be rude to patrons. Just simply say “Thanks for your input, I’ll discuss it with the appropriate people.” B E   N I C E. There’s no need to escalate.

In any performing arts situation, there is bound to be a lot of cooks in the kitchen. It is important to know who is in charge and what the chain of command is. It may be as simple as you working for the band. But it is also possible that there will be several levels of management over you, so make a point of trying to understand those subtleties and distinctions. If possible, try to get a grasp of that before you arrive. Here are some common scenarios:

BAR: Venue Owner > Sound Tech

CONCERT: Promoter > Band Leader > Sound Tech > Event Volunteers

MUSICAL: Theater Company > Auditorium Director > Tech Director > Sound Tech

CHURCH: Pastor > Create Arts Director > Music Director > Sound Tech

FESTIVAL: Festival Coordinator > Sound Company Rep > Sound Tech

Or, if you’re working directly for the band and in a festival type of situation, then your job would include some diplomacy and political skills so that you can provide what your band needs while also cooperating with others who may or may not have compatible agendas!

Being a great audio engineer requires a few different skills, including:
– an understanding and P A S S I O N for the arts
– a K N O W L E D G E of the gear, how it works & interconnects
– a knowledge of the F R E Q U E N C Y spectrum and how it applies
– a basic understanding of E L E C T R I C A L needs and processes
– an organized mind that can track S I G N A L   F L O W and troubleshooting
– the ability to think like a M U S I C I A N and anticipate changes

If not, it might be a good idea to take a few lessons. Having a foundational understanding of how music is performed and arranged could be a huge key to your success as a sound tech. Do you know what a verse, chorus, bridge, turnaround, build, half-time section, modulation, breakdown, second ending and coda are? If you want to work alongside musicians, then you better learn how to speak their language!

Components of a Pro Audio System


In this lesson, we will begin looking at the different components of a professional audio system. In articles to come, we will look in more detail at each component separately.

Source. This would include microphones, direct boxes, playback & other sources of audio.

Mixing Console. Where most of the action happens – the blending of inputs and outputs.

Processing. Various components which tweak and split the sound for various uses. Functions in a system processor would include Crossover, Gain, Polarity, Equalization, Delay, Merging & Splitting.

Amplifiers. Equipment that receives line-level inputs and delivers speaker-level outputs.

Loudspeakers. The various forms of transducers that convert electrical signal into acoustical energy. They are manufactured to optimally project a specific frequency range, i.e.: subwoofers, woofers, mids, and high-frequency horns.

It is important to get into the habit of speaking in terms of proper signal flow. Often, you will hear someone say “my amp is plugged into my guitar”. This is not correct. The guitar is the source. The sound travels O U T of the guitar, down the path of the cable, and I N to the guitar amp’s input. This same thinking applies to every input and output in an audio system. Force yourself so use the correct terminology, bearing in mind the direction of signal flow. You don’t plug anything INTO the output of a mixer! The mixer’s output plugs INTO the next piece of gear in the chain.

In a properly set up system, the console, processing, and amplifier inputs should all clip (reach the point of distortion, or overloaded signal) simultaneously. This gives you tha maximum headroom  (also called signal-to-noise ratio) out of the entire system chain.

Just a few years ago, the “processing” component of the signal chain was an entire rack or two of different pieces of gear. But in today’s reality of excellent quality digital audio processing, that same amount of processing (and more) fits in just 1 or 2 rack spaces. In addition, the proliferation of digital mixers and self-powered speakers means a lot of today’s signal chains look quite a bit different than those of just 15 years ago.

Understanding Signal Flow

Knowing the audio path through a mixing console is absolutely critical to a sound engineer’s success. Using this information, the engineer can quickly TROUBLESHOOT the likely causes of common problems, and can even narrow down the possibilities of unexpected major problems. It can also prevent mistakes because you know what the audio is doing at each stage of the console.

It also gives the audio tech CONFIDENCE as he sits behind the console. This is because he fully knows the ins and outs (sorry for the pun) of the equipment. Finally, it gives the audio tech a FOUNDATION of understanding which allows them to move from room to room or console to console and not be thrown for a loop. Instead of thinking, “the 2nd red knob on my old console was always set to 12:00, does that mean the 2nd blue knob on this console should be set the same?” The knowledgeable tech will know exactly what that knob is and where it is in the audio signal chain (even consulting the owner’s manual if necessary.)

You want to be an excellent all-around driver of vehicles, not a specialist who only knows and drives a Chevy Malibu 2-door with the small V6.

In general, the controls that you tend to “set” are at the top of the console, meaning you have to actually reach for them. The conrols that need more adjustments along the way are closer to your hands (i.e.: the channel faders.)

The channel strip tends to lay out generally “in order” as it applies to the audio signal flow – Gain, then EQ, then the Fader, for example. But this is a very broad overview. There is much more detail to be learned.

So how do you learn the signal flow of your paticular console? You break out the manual. It will contain what is typically called a “block diagram”. Now block diagrams can be headache-inducing nightmares. Check out this one for a Yamaha DM2000:

So I recommend that you take the time to create your own simplified signal flow. Just follow the lines on the block diagram to determine the signal path. It’s also recommended that you make it in linear, vertical orientation so that it helps you visualize the flow better. You can use any drawing or paint program to make one.

I have created a few Signal Flows for study. They can be extremely valuable learning tools. (Click on the images to see a full sized version). [Note: These images are for personal study only. Not to be used in any other websites or printed materials.]

Here is the signal flow of a Mackie 1604 VLZ.

And here is a larger format Yamaha IM8•40 console.

And here is an APB Dynasonics Spectra-C/56


Gain: A level adjustment designed to optimize each signal coming into the console.

Pad: If you turn the gain all the way to the left and the signal is still too hot, then you should engage the pad, which will reduce the incoming signal by a preset amount (usually 20 dB or so).

HPF: High-Pass Filter. A circuit which sharply decreases low frequencies, reducing mike handling noise, stage rumble, and plosives (p-pops).

Polarity: A simple switch which flips the polarity of the input. (Sometimes incorrectly labeled ‘phase’). Useful for eliminating phase-cancellation when using multiple mics on the same source (both the top and bottom of a snare drum, for example).

Insert Loop: A patch point for connecting outboard gear, such as a compressor or effects unit.

Direct Out: An individual channel output after the gain stage, but before EQ or fader involvement. Most often used for feeding multitrack recorders.

Aux mix: A separate mix of each channel which has its own output, which can be used to feed stage monitors, a recording mix, sends to a reverb unit, or other uses.

Pre/Post: An indication of where the Aux mix splits off from the main signal. If it is labeled as as “Pre” or “PreFade” mix, then its level is completely independent of the channel’s fader. If it is labeled as a “Post” or “PostFade” mix, then the aux’s level will also be affected by the channel fader as it is adjusted.

PFL: Pre Fade Listen. Works as a “solo” button for the engineer’s headphones. You can isolate an individual channel, and hear changes you make with the EQ. Because it is pre-fade, it does not matter where the fader is at the time.

Group/Subgroup: A Subgroup (or just “Group” on some consoles), is a tool used to help the audio tech during a service or performance. Rather than have to independently mix 32, 40, or even up to 56 channels on a console, you can assign for example, all the drums to one fader called a “subgroup”. The Subgroup does not affect any aux sends, it only affects the main mix. So I can raise or lower the level of all 8 drum mics on one fader – VERY USEFUL.

VCAs and VCA Groups: A VCA stands for Voltage Controlled Amplifier and is a common way to “automate” certain things on a mixing console. You can assign multiple channels to a VCA (just like a group), but the difference is – NO AUDIO IS PASSED THROUGH A VCA. Instead, the VCA acts exactly like a remote control to channels which are assigned to it. Where it gets really interesting is that channels that are assigned to a VCA Group DO NOT have to share a common audio path AT ALL. (This means you can have the entire band on one VCA fader, even if they all are routed to different mixes and subgroups!)

Something to keep in mind with VCAs that you don’t have to worry about with Groups: a VCA provides the exact same function as adjusting a channel’s fader (including any changes to it’s Post Aux mixes). This is different than a SubGroup, as a sub would only affect the house mix.

Buss: a common term seen in mixing console owner’s manuals. It is an electrical term rather than an audio term. Technically, an aux mix, a subgroup, a master mix, a mono output, a matrix output, etc. are all busses. The only way this term becomes important to an audio tech is in the possibility that you get some “buss distortion) which may not show up on the meters. If, for example, I assign all 32 channels of a console to SubGroup 1, and the console I’m driving doesn’t have Group Meters, and I keep the Group 1 fader low enough that I don’t get overloads on the Master Mix Meters, then it would be possible to overload the Group 1 buss, creating distortion, that would not show up on any meters. This is an extreme example to make a point – but I think you get it.

Matrix Mix: A completely different kind of output available only on the larger consoles. It’s sole purpose os to create an alternate mix to be used for recording, for routing a different mix to a different room, or for any other specialized purpose. You will not see a Matrix split on the following audio signal flows. Why? Because they are not made up of individual channels! A Matrix mix is created solely from mixing the Main Outputs and SubGroup Outputs. So a Matrix Out is created downstream from any individual channel functions.

The Order of Input Channels

There are lots of theories on channel layout. Some board operators prefer vocals first, followed by the band. Some use the opposite scenario, with the band first and then vocals. And some don’t give much thought to the process, just plugging things in order as they come from the stage (Stage Pocket 1, 2, then 3, etc.) regardless of what instrument is represented on that line.

Over the years, I have advised my clients and friends to generally adopt the “Pyramid Mix” channel order. For those of you not familar with the Pyramid Mixing technique, here is a diagram (created by Curt Taipale) which explains the concept:

So how do you build a pyramid? You start with the bottom layer and work your way up. I do modify it slightly, in the sense that I want to keep like instruments together (guitars, keys, drums, etc.). Also, in most settings I’ve worked with in the last several years, guitars are dominant with keys being primarily ambience (organs, pads, etc.) – so the pyramid is slightly modified there. It’s also helpful if you lay out the channel order with regard to your Groups. The typical large format board has 8 subgroups, so I take that into consideration as well. So here is the general layout I recommend to most clients:

01 – Bass Gtr
02 – Kick Drum
03 – Snare Drum
04 – Tom 1
05 – Tom 2
06 – Tom 3
07 – Hi Hat
08 – Crash (OHL)
09 – Ride (OHR)
10 – Percussion 1
11 – Percussion 2
12 –
13 – EG 1
14 – EG2
15 – AG 1
16 – AG 2
17 –
18 – Piano L
19 – Piano R
20 – Synth L
21 – Synth R
22 – Track
23 – Click
24 –
25 – Lead Vox (or Worship Leader)
26 – BGV 1
27 – BGV 2
28 – BGV 3
29 – BGV 4
30 –
31 – Anouncement Mic
32 – Pastor Mic

Notice there are some blank channels in between the groupings. This is for that last-minute request that always seems to come, ie: “Bob is going to be using 2 amps today”, or “I fogot to tell you we’ll need 3 acoustic channels this week”, or “We’re using the Djembe today so we need 3 percussion mics.”

Of course, this order can be scaled up or down depending your exact situation, but now let’s look at the group situation. Here’s a look at the typical 8-group layout:

Group 1 – Bass/Kick
Group 2 – Drums (all drums/percussion except Kick)
Group 3 – Electric Gtrs
Group 4 – Acoustic Gtrs
Group 5 – Keys
Group 6 – Misc (could be brass, choir, lavs, whatever)
Group 7 – Lead Vox
Group 8 – BGVs

You may have to make some modifications if you are running true stereo. Group 1-2 may be Stereo Drums. Group 5-6 may be Stereo Keys, etc.

If you only have 4 groups, it might look like this:

Group 1 – Drums/Bass
Group 2 – Gtrs
Group 3 – Keys
Group 4 – Vocals

I realize this specific layout may not work for everyone, but it has proven to work in many situations I’ve been involved with over the last several years. Whatever layout you choose – it should make sense and should allow you to mix properly without having to go hunt for something.


Audio Training for Live Sound. All content ©2010 Jeremy Carter Consulting.

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