Basic PA systems

Simple sound systems for beginners

This is an old document previously located and edited on the aktivix wiki
I’ve pulled it over here to crabgrass for convenience.

‘’This page is intended to be a simple guide to PA systems for autonomous spaces – how to set them up and how to use them. It is beyond the scope of such a guide to provide comprehensive instruction of how to use all PA equipment and sound engineers require years of training and on the job experience. There is no substitute for getting in somebody who knows what they are doing and learning from them.’’

= PA system basics =

== Components ==

At its simplest a PA consist of mixer, amp and speakers (plus a sound source obviously). The mixer can be a microphone mixer or DJ mixer depending on the application.

= Amplifier and Mixer =

Amplifiers are rated in watts RMS and care must be taken not to exceed the capacity of the speakers which are also rated for max watts. It is also necessary to match amps and speakers in terms of ohms. PA speakers are usually 8 ohms but can be wired in series to provide 4 ohms which is as low as most PA amplifiers will go. The system can be mono or stereo but wiring for mono is easier, cheaper and louder.

= Speakers and Stands =

The speakers should be placed at the front of the stage or performing area, at either end. They should be mounted at a height above the head height of the audience. This is to prevent the sound from being blocked by people standing in front of the speakers. Bass speakers should sit on the ground.

Singers should not be in font of the speakers as this is likely to cause problems with feedback. Feedback occurs when microphones picking up the sound from the speakers which is then amplified again and played back through the system in a loop. Feedback sounds like a high pitched squeal which is not pleasant to listen to and is likely to damage speakers.

= Stage Monitors =

A PA system set up for live performers is likely to require a monitor (or fold back) system so that the musicians and vocalists can better hear their own role in the mix. This normally consists of wedge shaped speakers placed on the stage facing diagonally up towards the performers and driven by a separate amplifier feed by a signal from the ‘monitor send’ on the mixer. These days, monitors are often active speakers which have an amplifier built in. They don’t need to be super powerful, 100 watts is plenty.

= Additional Components =

Beyond the basic system there may be effects units and other signal processing such as graphic equalisers, compressors, limiters and crossovers. These generally go in the signal path between the mixer and the amp.

  • Effects units enable you process and hopefully improve your sound. For example, adding reverb or delay to vocals (especially if the vocalist can’t sing) or applying some compression. You rarely want modify all the sounds passing through your miser so effects units are connected to specific channel on your mixer via outputs called ‘FX send’ then added to the final mix via inputs labelled ‘FX return’. You can then choose which channels are routed to the effects units by adjusting the FX pots.
  • A graphic EQ is useful to cut out frequencies causing feedback and allow a generally louder output at all other frequencies. It is most useful on your monitor system so if you only have one EQ unit, use it there. The EQ is placed between the output of the mixer and the input of the amp.
  • A feedback destroyer/eliminator helps eliminate feedback. The cheapest are built into qraphic equalisers and merely identify which frequencies are causing your feedback problem and leave you to fliter out that frequency. More expensive ones apply filters in real time. They are apparently not normally used in professional live audio. However without a professional sound engineer you might find one very useful.
  • A compressor/limiter/leveller is a good idea to ensure that the speakers are not damaged by feedback or amplifiers peaking beyond the capacity of the speakers. It is important that it is in the signal path after any effects or any EQ. (see wikipedia)
  • An active crossover is useful when putting together a bi-amp system where different amps drive different speakers at different frequency ranges to provide the most efficient and loud output. Effectively it splits your signal so that low frequencies go on way and hi frequencies go another. The crossover should be the final item in the signal path before your amplifiers.

= Back Line =

The above describes what is known as the front of house system. There is also the back line to consider which is all the speaker and amplifier heads used by the musicians on the stage itself, ie. guitar, bass and keyboard amps. These are generally supplied and set up by the bands and not provided by the house.

It seems common for the musicians to be deaf and having all their equipment on the highest volume available so you are forced to compete to ensure the vocals can be heard. Unfortunately the sound engineer has not direct control over the level of any of back line so you must communicate with the musicians during sound checks to ensure their levels are set at a reasonable level for the venue and stay that way during their set.

= Buying a PA =

Ask yourself these questions. What will it be used for now? What is it likely to be used for in the future? Where will it be used? Who will operate it? How will it be paid for initially? Who will maintain it and how will that be paid for?

Like many things, it is probably worth investing more upfront to avoid the need to spend more later. You might have a really small venue now but next year you might have a much bigger place or you might be loaning the kit out to other spaces. Having said that, be realistic, are you really going to be banging out tunes in front of 5,000 people in an aircraft hanger every weekend? Are you really going to have a 20 piece choir on stage? The bigger the system the more expensive everything gets. Look at other places and the PA they use. Ask for advice from sound engineers and party crews.

It’s generally good advice is to buy the most powerful power amp you can afford. If you don’t need its full output capabilities at that small indoor gig, that’s fine – it will sit there and deliver low-level sound with negligible distortion year after year. But when you need to really crank up the system in a large hall or outdoors, you will be happy you paid for the extra power.

== Volume, Watts and Ohms ==

As a rule of thumb, a small pub with a capacity of up to 100 people will be manageable with a 300W system (2x 150W RMS). For a venue with up to 200 people then 600W (2x 300W RMS) should do the trick. In a large halls with perhaps 400 people you’d be looking at a system capable of a good 1000W (2x 500W RMS) or more.

However, before worrying to much about power ratings, it’s important to understand volume levels. Volume levels are measured in decibels (dB), either relative to something else or absolute (usually given as SPL which means sound pressure level).

Speaker systems are usually shown with an absolute measure, like “104dB @ 1 Watt, 1 metre” which means that the speaker produces a sound pressure level of 104dB when measured 1 metre away using a 1 watt signal. As a guide 60dB is the level of normal conversation while 120dB is threshold of pain. An increase of between 6dB and 10dB is perceived by most listeners as “double” the volume. ( more info).

Driving a speaker with 200 watts will produce just 3dB more volume than it did with 100 watts. To double the volume would require at least 400 watts and to double it again would require over 1600 watts! This means that the difference between a 400 watt amplifier and say a 1000 watt amplifier isn’t really all that much.

Just to confuse you and make it easier for manufactures to sell shit, power rating of equipment is done in different ways. Power should be measured as continuous watts RMS but you also see things like ‘programme power’, ‘music powre’, ‘maximum power’, ‘PMPO’, etc etc. The ‘programme’ figure is usually twice that of the RMS figure while ‘peak’ figures can be three or four times higher. It’s all nonsense. Power can be measured in such dubious ways that you can find some manufactures advertising 10 watt RMS systems as 1000 watts PMPO! The only measures worth a damn are the RMS figures.

There is another opportunity to get confused. Each loudspeaker has an electrical characteristic called the Impedance and is expressed in Ohms. It is a measure of the resistance offered by the loudspeaker. An amplifier may output 200W into 4 ohms speakers but just 140W into 8ohms. Most PA speakers are 8 ohms. If you wire two together in series then they’ll present 16 ohms but if you wire them in parallel then you’ll have made 4 ohms. Amplifiers can safely handle driving power into speakers only when they fall into a specific range of ohms – too high or too low and you’ll damage the amplifier.

== Choosing Speakers ==

Contrary to popular belief, a 200 Watt speaker will not sound twice as loud as a 100 Watt Speaker. Of course it will handle more power and there work with more powerful amplifiers, but whether it is louder depends on another factor, and the speakers ‘Sensitivity’ which is given as SPL.

SPL is the measure of how efficient a loudspeaker is at turning power (Watts) into actual sound (Decibels). The higher the SPL figure the more efficient a speaker is and the louder it will sound. For example it is possible to buy a 100W speaker with an SPL of 104db and it will sound much louder than a 200W speaker with an SPL rating of 92dB!. A difference of 6dB is a doubling of volume and you’d need to quadruple your amplifier output to provide the same increase. In other words you’d need 400 watts to drive speakers with a sensitivity of 92dB to the same volume as speakers rated at 104dB being driven by 100 watts!

Invest in speakers with a high sensitivity and it will save money and energy.

== Matching Amps to Speakers ==

How many watts should your speaker handle vs. the size of your amplifier? To answer that we must consider how a speakers can fail. There are two basic ways – thermal failure and mechanical failure.

Thermal failure is when a speaker is stressed to the point from too many watts (of “clean” sound — more on that later) for too long a time that it just overheats and seizes.

Mechanical failure usually occurs when a speaker is driven by an overloaded amplifer putting out distorted or clipped sound. This distortion quickly kills speakers, pushing the cone beyond it’s designed limits, potentially tearing it to pieces. It is entirely possible to blow out 300 watt speaker with a 100 watt amplifier if you drive it into clipping.

So the key is to match your amp output with your speaker’s ratings. If you have speakers rated at 300 watts , match that with an amp that puts out at least 300 watts per channel. You can use an amp with less power, but be care not to overdrive it. If possible, use an amp with a higher output rating than your speaker load. You reduce the risk of clipping and hurting your speakers, and you end up with a lot more headroom and dynamic range available, which enables your system to reproduce transients much more effectively and with less distortion, which in turn just makes things sound better and reduces ear fatigue in the audience.

A good rule of thumb is to pick an amplifier that can deliver power equal to twice the speaker’s continuous power rating. This means that if you have a pair of 8 ohm speakers rated at 250 watts each, you’ll require an amplifier that can produce 500 watts per channel at 8 Ohm load.

If you can prevent the power amp from clipping (by using a limiter), use a power amp that supplies 2 to 4 times the speakers continuous power rating per channel. This allows 3 to 6 dB of headroom for peaks in the audio signal. Speakers are built to handle those short-term peaks. If you cant keep the power amp from clipping (say, you have no limiter and the system is overdriven or goes into feedback) the amplifier power should equal the speakers continuous power rating. That way the speaker wont be damaged if the amp clips by overdriving its input. In this case there is no headroom for peaks, so youll have to drive the speaker at less than its full rated power if you want to avoid distortion.

If you are mainly doing light dance music or voice, we recommend that the amplifier power be 1.6 times the Continuous Power rating per channel. If you are doing heavy metal/grunge, try 2.5 times the Continuous Power rating per channel. The amplifier power must be rated for the impedance of the loudspeaker (2, 4, 8 or 16 ohms).

Here’s an example. Suppose the impedance of your speaker is 4 ohms, and its Continuous Power Handling is 100 W. If you are playing light dance music, the amplifier’s 4-ohm power should be 1.6 × 100 W or 160 W continuous per channel. To handle heavy metal/grunge, the amplifier’s 4-ohm power should be 2.5 × 100 W or 250 W continuous per channel.

If you use much more power, you are likely to damage the speaker by forcing the speaker cone to its limits. If you use much less power, you’ll probably turn up the amp until it clips, trying to make the speaker loud enough. Clipping can damage speakers due to overheating. So stay with 1.6 to 2.5 times the speaker’s continuous power rating. more info

== New or Second Hand ==

For environmental, ethical and economic reasons you’ll probably want to buy second hand. Effects, compressor limiters, equalisers etc. are all pretty reliable and fairly safe to buy used. Modern amplifiers are quite cheap due to advances in power supply technology (nice and light as well) but older amps are often considered better, more reliable and easier to fix. There is little difference in price either way. Second hand mixers can be a bit random so make sure you test them well. The most important part of you PA is the speakers and you might want to consider buying them new. If you do buy used speakers, find out how old they are and why they are being sold. Speakers do deteriorate with age and abuse so test them well.

All prices below are based on second hand prices.

== Example Systems ==

= Compact PA =

As a very rough guide, a space like LARC in London might use a 100 watt PA, with an emphasis on quality rather than volume of sound. It might as well be a compact portable unit, easy to put away in a safe place when not in use or loan out for events elsewhere. It would have a minimal mixer with perhaps four inputs. It would likely be used to provide audio for film screenings and mic up a vocalist and guitar for small acoustic gigs.

= Small PA =

For a venue like Sumac or rampART a PA between 400 and 800 watts would do the job. A mixer with six or eight mic inputs should cope with anything you are likely to do in such a space. You could keep it simple with an all in one mixer amplifier – they often also include an EQ plus effects such a reverb and delay which makes them easy to setup and use.

= Full PA =

A space doing regular gigs would need a more complete PA with stage monitors. A couple of 300 watt full range speakers, limiter and a 1000 watt amplifier for front of house, then monitors, 100 watts (perhaps active speakers that include built in amps) plus graphic EQ. Mixer should be eight channels or more, ideally with built in effects.

  • 1000 watt amplifer ~£80 – £120
  • 8 channel mixer ~£100 – £150
  • Pair of 300w RMS speaker ~£150 – £400
  • 31 band EQ ~£40
  • limiter ~£40
  • Active monitor speaker(s) ~£100 – £150

= 12 Volt / Pedal Powered PA =

A sound system powered by 12 volts is a handy thing if you want to be able to provide a system away from the availability of mains power. You can power it from 12 volt batteries and recharge, if need be, using solar, wind or even pedal power.

While it’s easy to get a 12 volt amplifier, it is not easy getting mixers and effects that run on 12 volts. Now that invertors that turn 240v AC into 12v DC are so cheap, it’s common to see 240v equipement being used even if the amplifier is run on 12.

The most vital thing to consider is the efficiency of your speakers. It makes a massive difference in the amount of power you’ll use if you used 90dB SPL card speakers compared to 108dB SPL PA speakers. Remember, each 6dB increase in efficiency means you need 75% less power to create the same level of sound.

Consider a bi-amped system with an active crossover Class D amp driving the bass. Stick with mono and a single speaker stack for less weight.

  • Active crossover (car audio) ~£20
  • 2x 250 watt RMS car audio amp ~£40
  • 1x 200 watt RMS class D car audio amp ~£50

= Using a PA =

== Setting Up ==

You plug your sound source into your mixer inputs, link the mixer output to the amplifier inputs and attach the speakers to the amplifiers main output. Make sure all levels are at zero before you switch the system on.

The components of the system should be switched on in the following order – Effects then Mixer then Crossovers then finally the Amps. This order keeps the majority of the popping signals created by that initial power surge when each component is turned on from ever reaching the speakers. The main thing to remember is that the amps should be turned on last and turned off first.

Whenever turning anything on (or off) that is connected to the PA system (microphones, keyboards, acoustic guitars…), make sure that the “monitor” knob and the “level” slider for the channel it is plugged into is pulled all the way down.

When everything is set up and all your sound sources / microphones etc are plugged in, double check that everything has been wired up correctly. If your PA is permanently set up in the venue but other people have had access to it since you last used it, check it all again in case some idiot has come along and bypassed your limiter or wired the amp outputs into the mixer (both have happen to me).

== Setting levels ==

When you are satisfied that everything is as it should be, then you are ready to test your inputs and roughly adjust their levels. Start off with all levels to their minimum, including mic and line trim pots. Now turn the amplifier on and turn its volume up all the way. Set the main output slider on the mixer to about 2/3 the way up where it is labelled 0db – the final volume will be controlled from the mixer not the amplifier.

Start with a test using a recorded sound source like an mp3 player or cd then if everything sounds ok you can move onto setting up the mics. Make sure that all the mics are switched on (some have on/off switches on the mic, others don’t). Start with the first mic channel on the mixer and slowly bring the slider up. If it you start to hear feedback then slide it down until it stops and check that your trim pots are all the way down. You should be able to get the slider up to 2/3 of the way up by the 0db label. Leave the slider at 0db and now slowly bring up the mic trim pot until you start to hear feedback then turn it down just a little. Do the same for each microphone in turn then you are ready to adjust the levels for keyboards, cd players etc.

  • Set the master level fader at around two-thirds maximum and the microphone faders at maximum. Turn the input gain trims right down.
  • Gradually turn up the microphone gain trims one at a time until the microphone just starts to ‘ring’, then, back it off just a hint.
  • When you have done this for all the vocal microphones, pull their faders back down to the 0dB unity gain position (full up is usually +10dB). This leaves you with around 10dB of headroom before feedback again becomes a problem.
  • Now simply balance the instruments to this vocal level by doing a quick run-through of a song or two during the sound check.

== Ringing out the room ==

The practise of setting individual microphone levels by finding the point at which they feedback is described above. If you have an EQ in your system then you can also ‘ring out the room’ to eliminate feedback problems while maximising your potential volume. Ringing out is very common for monitors; less so for ‘Front Of House’.

Ringing out the system is a process of eliminating frequencies that cause feedback. It is especially helpful in small rooms or in large venues where stage monitors are extremely close to microphones or any other microphonic device where feedback can easily result due to proximity. The process of ringing out the system will take time to get used to, but with some practice it will become easier as you learn what frequencies are the more likely culprits.

Ringing out involves adjusting each band on your graphic equaliser so that frequencies which produce feedback are brought down in level (notched out) while the overall volume is pushed up. Too much ringing out will remove frequencies you need for the music so it’s always a compromise. Ideally, if you have time and stage space, it is better to position speakers, microphones and monitors in such a way that feedback isn’t a problem in the first place.

Once you have your overall mix levels more or less worked out, you will then want to set all of your main mix graphic equalizer sliders to “0”. You will then raise the system gain slowly until you start to hear feedback (ringing) in the system. Track down the proper slider and reduce the level until the ringing ceases.

Slowly continue to bring the system gain up once again until another frequency begins to ring. Again, you will want to reduce this offending frequency. You will continue to do this until several frequencies begin ringing at the same time. At this point you have reached your maximum headroom of the system. Back the gain down to the point that the ringing ceases.

== Labelling ==

Your sound check will be much easier if you have labelled the ends of all your XLR leads with numbers or colour coding. This makes it easier to identify which sound source or microphone is plugged into which channel on the the mixer. It is also common practise to stick some masking tape under the sliders on the mixer and write notes to indicate which input is being used for what on stage.

While you are labelling your cables you might as well label everything else so that it’s obvious who each bit of kit belongs to at the end of the night. You could also label things up with mini instructions to help ensure that things set up and used correctly.

== Sound Check ==

There are two reasons to soundcheck. One is to get a good sound for the audience, the other is to get a good sound on stage, for the band. If you’re in a smaller venue, then you’ll generally find that you only need to put the vocals through the PA, everything else will be using the sound of the instrument or amp directly.

A sound check is not meant to be a final rehearsal for the band or a warm up, it is a time to work on sound rather than music. Use the words “Two” and “Check” when you check a microphone. Believe it or not, there are practical soundguy reasons why these words are so common in soundchecks. The “Ch” part of “check” checks how the highs and mids sound, the hard stop made at the “ck” sound helps check how the effects are working, and the word “two” (or “four” if two gets boring) really helps to see how the lows on the mic are sounding. Don’t have a conversation on the mic, just say “check – Two” and repeat. . . and repeat. . . and repeat. .

With “standard” rock bands, most engineers will check in the following order: Kick Drum, Snare Drum, Hi-Hat, Rack Toms, Floor Toms, Drum Overheads, Full Drum Kit, Bass Guitar, Keyboard, Rhythm & Lead Guitars, Vocals, Whole Band. With other kinds of performance, it is common to check Percussion first, Backing Instruments second, Lead instruments third, and Vocals last.

Do not let the guitar player determine the decibel level of the entire PA system! Colossal volume from electric guitars and other instruments can be great fun for the person playing them. However, intelligibility, separation, and the cohesion and coherence of the whole mix will be greatly improved if you keep backline levels down. The most difficult part of being an effective live sound engineer in a small venue is communicating this to the band.

The quieter the sound on stage the easier it is to get a good sound out front. Less is better: any sound from the monitors will contribute to onstage spill (reducing separation), and will also be reflected into the audience by back stage walls. High levels on stage will seriously compromise the front of house engineer’s ability to control the sound the audience hears.

== Look after your ears ==


While you can expose yourself to whatever sound levels you like, if you like listening to music and want to continue enjoying it for many years to come, look after your ears. Standing to close to PA speaker stacks will expose you to potentially excessive noise levels. You may have a slight ringing noise after if you over expose yourself. This can cause long term damage to your ears.

If you intend to spend a long time in front of the stage remember to give your ears a break. It is common for professionals to wear ear protection when working in close proximity to a large PA. Look after your ears, you only get one pair. Likewise, consider the effect of excessive sound levels to those attending your events.

= Glossary of terms =

Amplifier (Power amp, Head) – It’s the part of the sound system that actually magnifies or “amplifies” the sound. In other words, it makes stuff louder.

Trim Pots – The electronic component under the knobs that varies the strength of the signal running through it. When these get old and dirty, they can make poppingand crackling noises through your PA when you touch them.

Balanced input/output – A “balanced” connection is one that has three wires to move the signal. One is a ground, and the other two (called conductors) carry signals of equal value. This is why they are called balanced.

Bottom – The bass frequencies (as in “needs more bottom end”).

Bridge Mode – a feature built into most stereo amplifiers is Bridge Mode. When in Bridge Mode the two channels in the amplifier are electronically linked to form a single channel with increased output power.

Cable, 1/4 inch Jack – An unbalanced cable most often used for instruments and patch cords. Commonly referred to as “guitar cords”.

Cable, XLR – A balanced cable used for low impedance microphones and sometimes for connections between some parts of the PA. Commonly referred to as a “mic cord”.

Channels – These are divided into two separate categories. Input channels are those coming into the mixer such as microphones and direct lines. Output channels are those leaving the mixer or amplifier such as monitor and main outputs.

Clean – Describes a distortion free sound with few effects.

Compressor – Effect used to squash the sound together. Used properly, it can take the edge off or your sound. Used improperly, it can take the life right out of your system and make it sound like an MTV mix.

Crisp – Describes a good clean high midrange sound. It can be good or bad depending on the look on the face of the guy who said it.

Crossover, Active – A rack mountable unit used to separate frequencies leaving the mixer into high’s, mids, and lows with different outputs for each.

Crossover, Passive – Used inside of full range speaker cabinets to separate highs, mids, and lows and send them to their respective speakers within the each cabinet. These are not as efficient as active crossovers because they require all frequencies to draw from the same source of amplification.

Cord (Speaker, Mic, Instrument) – Used to connect a sound system together. Each type of cord is made for a specific purpose and should not be used in place of another type of cord, not even if they look alike. Also see “cable”

Delay (Digital, Analog) – 1)Effect used to create echo…echo…echo…echo…echo… 2)In more advanced systems used in very large venues, delay can be used to time the arrival of the signal to the speakers in the back of the room so that people in the back hear the sound coming from those speakers at the same time that the sound coming from the speakers in the front of the room arrives.

Direct box / DI Box – Used in line to convert a high impedance signal into a low impedance signal.

Distorted – The way your PA sounds just before it blows up. Fuzzy and scratchy. If you hear this, it either means you have something hooked up wrong, or something in the system is going bad. It could be anything from your super expensive mixer to cheap patch cord.

Dry – Describes a sound coming from the PA with no effects on it.

Effects – Electronic boxes (usually rack mounted) added to a PA system to subtly change and enhance the signals going through it. Examples include; Reverb, Delay, Compressor, Chorus.

Equalizer (Parametric or Graphic) – This is used to filter out and adjust specific frequencies in the PA. This is the part of the PA where you have the most control over the band’s overall sound. It is also the number one weapon against feedback.

Feedback – This occurs when the sound coming out of the speakers goes back into the microphones, then back out the speakers, then back into the mics…. and so on. This can build very quickly to a point where everyone in the room is holding their ears and screaming at you. It can also cause damage to the PA.

Flat – Refers to the frequencies on the EQ when they are arranged in centered neutral positions.

FOH (Front of House) – Refers to the speakers that face toward the audience. Also called the “main” speakers.

Frequency – Practically speaking, high frequency means high pitch and low frequency means low pitch.

Full Range – Describes a sound which covers all audible frequency ranges. As in “full range speaker cabinets.”

Gain / Trim Pots – Knobs usually found at the top of each input channel on the soundboard. Used to set input levels of the separate channels to relatively equal positions.

High Impedance Cord (High Z) – A big word for instrument cable. These cords generally have quarter inch male ends. they tend to loose signal strength at lengths longer than 25 feet.

Horn – The part of the speaker that emits midrange and higher range frequencies.

Fader – Sets output volume of individual PA input channels. Usually positioned as sliders at the bottom of the mixer.

Loop (Effects Loop) – A signal path separate from the main signal paths where a line signal is routed out of the mixer through a series of effects units, and then returned back to the mixer. The electronics within the mixer can then be used to individually control the effects on each input channel.

Low Impedance Cord (Low Z) – A big word for mic cable. These cords lose very little signal over distance, and can thus be made very long. PA snakes are constructed mostly of Low Z cords because of their need to be lengthy.

Line Level – A low level signal such as the signal in a guitar cord. Most parts of a PA require a line level signal.

Monitors / Fold Back – The speakers facing back onto the stage and the system or amps, equalizers, and effects attached to them.

Monitor Mixer – Larger systems often use a completely separate mixer for the monitors that only adjusts the sounds that are heard on the stage.

Muddy – Describes a low end muffled sound lacking highs and mids, and possibly having too much effects.

Pan (Balance) – Knob on the mixer that adjusts the relative volume between left and right (or A and B) in a stereo setup. Just like the stereo in the living room.

Patch Cord – A very short high Z instrument cable.

Phantom Power – When this is turned on in the mixer it will power the active microphones in the system. It should be turned off when no active mics are hooked up.

Reverb – A most basic and necessary effect. Think of it like this. If you stand in a big empty warehouse and shout, “Hey!”, you will hear a sort of “reverberation” surround you. It’s sort of like an echo, but not exactly. Think of it as audio afterglow.

Slider – These turn things up or down by a “sliding” movement rather than the rotary movement employed by knobs.

Snake – In large systems, this long bundle of cords connects the things on the stage (amps, mics…) to the things at the sound booth (mixer, effects, EQs…..).

Speaker – The part of the system that physically produces the sound.

Speaker Cabinet – The box that holds the speakers.

Speaker Out – A high power signal leaves the power amp through this jack on it’s way to the speaker.

Submix – Used on larger mixing boards when selected channels are assigned to specific sub-channels before their signals reach the main slider. For Example, you could assign all the drum channels to one submix (all on one slider) so that you could turn them all up or down at the same time.

Tinny – Used to describe a sound with too many highs and mids and not enough lows.

Unbalanced Input/Output – These cables contain 2 wires inside of them. One is a ground (shield) and the other carries the signal. The most common of these for PA uses are the 1/4 inch high Z instrument cables and connections.