PA's and Mixers

[hitchy64]

Hi all, i'm just getting into a band for the first time, we are having our first meeting tomorrow night. What is the differance between having a PA system and just useing our amps, and why do we need, or what does, a mixer do?? Cheers Hitchy

[BOD2]

Phew ! Bit of a big question there but let's see what we can do.

Firstly PA is also sometimes called FOH (Front of House) as in a large venue these are the speakers that produce the sound the audience at the front of the house hear. Your own amps are known as the "backline" ans are what produce the originalsound and what you on stage hear.

Your backline will amplify all of your instruments.

If you have a singer he'll need an amp/speakers for his/her vocal mic. This would be a "vocal PA" as it's for the vocals only. The size (power) of the vocal PA depends on the volume required.

If you start to play larger venues you might find the the backline is not loud enough to project to the back of the venue, or of you turn upo the backline loud enough you on stage are deafened or cannot hear the rest of the band. Now you have a problem. You need more volume but more volume will cause more problems on stage.

The answer is to amplify the backline through a PA. You can take a mic and put it in front of each backline amp then feed these mics into a PA. Now the backline volume can be kept lower and the PA will amplify the sound for the audience. That is the basic principle behind a PA.

Now if you have 3 singers each with a mic, two guitars mic'd up and a bass mic'd up you've now got 6 mics and need somewhere to plug them all in and balance the relative volumes of each. That's what a mixer does. You plug the mics into the mixer, set the leves for each mic using the mixer controls, then feed the combined (mixed) signal into the PA amps and speakers.

That's it, in very basic terms. One thing at a time - first understand the way that lot works then start having a look at what is out there and how you might use it.

To determine what you actually need you first have to answer some basic questions -

1. How many mics and instruments will you need to amplify (i.e. how many "inputs" do you need) ?
2. What size venues will you be playing ?
3. How much do you have to spend ?

[Happy Jack]

If you're going to use amplified voices, then you'll need microphones to sing through. Just like your bass, a mic won't make much noise unless you run it through an amp/speaker set-up of some sort. When you do that with microphones it's called a Public Address system or P.A.

If you have several microphones for different singers, or for a lead singer plus backing vocals (BV's), or for singers plus mic'd-up instruments such as acoustic guitars, then you don't want everything coming through one channel and you don't want everything at the same volume.

In order to control the 'mix' of sound sources and volume levels, you need a ... ta-daaa! ... mixer or mixing desk.

If you were planning to feed the vocals through your guitarist's combo or (God help us) your bass rig, then ... erm ... don't.

Any half-decent venue will already have a PA. If you're booked to play somewhere with no PA, then offer to hire a PA for the gig ... at the venue's expense of course.

Edit: Dammit BD, will you stop doing that!

Edited November 10, 2008 by Happy Jack

[BOD2]

[quote name='Happy Jack' post='326292' date='Nov 10 2008, 08:59 PM']Edit: Dammit BD, will you stop doing that! [/quote]

Sorry Happy Jack - I must have been typing faster than you ! But it's best to get more than one opinion anyway....

[hitchy64]

Cheers guys, that has explained alot. Can you plug the bass and guitars straight into the mixer and then back to our amps??

[Stewart]

To put electric instruments through the PA without using mics on the cabs you use a thing called a Direct Injection (DI) box, which splits the signal into a balanced one that'll suit the mixer (and can be run a long distance) and effectively a copy of the original signal which goes on to your amp as usual.

Like everything else DIs can be cheap or expensive, but I suspect you can't get a really bad one...

[BOD2]

[quote name='hitchy64' post='326352' date='Nov 10 2008, 10:21 PM']Cheers guys, that has explained alot. Can you plug the bass and guitars straight into the mixer and then back to our amps?? [/quote]

It depends on the mixer. Generally it's better not to do it that way.

For a bass guitar you can either use a "DI box" as suggested by Stewart or your amp may have a "DI out" connection at the back which is designed for this purpose.

For a 6-string guitar you generally need to "sound" of the speakers to get warmth into the sound. A DI guitar sounds pretty awful unless you're into ultra-clean guitar sounds. For a guitar you usually put a mic in front of the amp or you could use an "amp modeller" FX unit, but since these generally sound different to the amp sound your guitarist will almost certainly want a mic.

Acoustic guitars are mic'd up but these can be quite tricky to get a good sound. An electro-acoustic (with a built-in piezo pickup or similar) is a more practical solution.

Keyboards, if you have them, can go straight into the mixing desk.

If you play larger venues you cam also mic up the drum kit to boost the volume of this at the front. This is a bit of a black art but you'll need several mics for this and would be best seeking advice online for details.

[Happy Jack]

[quote name='hitchy64' post='326352' date='Nov 10 2008, 10:21 PM']Cheers guys, that has explained alot. Can you plug the bass and guitars straight into the mixer and then back to our amps?? [/quote]

+1 to Stewart's and BOD's responses, but reading your question literally you really do NOT want to take the signal to the mixing desk and then back out from the mixing desk to be the input to your amps or combos.

If you take the signal to the PA by using a DI box, then the idea is that your bass plays through the PA. If you want to play through the PA but also through your own amp, then you need [i]either[/i] a way of splitting the signal from your bass so that it goes to BOTH, [i]or[/i] you need an amp that is also a DI box. My Eden WTX260 does this for me, but that's hardly a cheap solution.

In very general terms, guitarists HATE playing through the PA and with very good reason. For bassists it's a far more useable proposition and can sometimes be a life-saver. As long as your gig-bag contains a DI box and a balanced DI cable then you can stop worrying about your amp blowing up ... in two minutes your bass can be plugged through the PA.

Edited November 10, 2008 by Happy Jack

[LukeFRC]

although if you are just starting in a band play venues that have their own PA and soundmen and you only need to worry about bringing your own amps.

[acidbass]

[quote name='hitchy64' post='326352' date='Nov 10 2008, 10:21 PM']Cheers guys, that has explained alot. Can you plug the bass and guitars straight into the mixer and then back to our amps?? [/quote]

It's pretty much all been said, but to simplify the brilliant responses given by Bod2, Happy Jack and Stewart, it goes like this -

[indent][list=1]
[*][b]Guitar[/b] to
[*][b]Amp[/b] to
[*][b]Microphone[/b] to
[*][b]Mixing Desk[/b] to
[*][b]PA Speakers[/b]
[/list][/indent]

..all connected using the required cables. If you wanted, you could put an effect between points 1 and 2, or even 4 and 5

For bass, it's simply -

[indent][list=1]
[*][b]Bass Guitar[/b] to
[*][b]DI Box[/b] to
[*][b]Mixing Desk[/b] to
[*][b]PA Speakers[/b]
[/list][/indent]

You can then take a connection out from the DI box into your amp to hear yourself on stage.

And for vocals, simply -

[indent][list=1]
[*][b]Microphone[/b] to
[*][b]Mixing Desk[/b] to
[*][b]PA Speakers[/b]
[/list][/indent]

The above is also true for mic'ing drums.

Hope this helps mate

[stingrayfan]

If you're playing pubs and small venues you need a PA just for vocals. Use your backline amps for everything else.

[spinynorman]

[quote name='stingrayfan' post='326514' date='Nov 11 2008, 09:09 AM']If you're playing pubs and small venues you need a PA just for vocals. Use your backline amps for everything else.[/quote]

From the recent experience of young bands just starting out that I know, this is your most likely situation. You may be able to get away for a time without a PA, because as has already been said, some venues have their own, or hire one in, or you may be playing support to a band that will let you use theirs. The only other possible need then is rehearsal, but if you use a properly equipped rehearsal studio, you can use theirs.

If you decide this isn't working, the minimum you need for vocals is a powered mixer (eg Yamaha EMX212s) and a pair of passive speakers (eg Yamaha AX12). There are loads of other makes besides Yamaha and you can buy secondhand to save money, but just watch you don't buy something so old it is unreliable. Ideally the speakers should be at head height, so you also need speaker stands. You can put several singers (and keyboard if necessary) through this sort of setup.

[url="http://www.imuso.co.uk/ProductDetail.asp?StockCode=PA00462"]http://www.imuso.co.uk/ProductDetail.asp?StockCode=PA00462[/url]
[url="http://www.imuso.co.uk/ProductDetail.asp?StockCode=PA00223"]http://www.imuso.co.uk/ProductDetail.asp?StockCode=PA00223[/url]
[url="http://www.dv247.com/invt/30124/product.htm?gdftrk=gdfV2356_a_7c416_a_7c1181_a_7c30124"]http://www.dv247.com/invt/30124/product.ht...c1181_a_7c30124[/url]

You could alternatively buy a PA package like the Stagepas 300, which is cheaper, but I don't know how good they are.

On top of that it is a good idea to have a monitor (eg Carlsboro PM10), which plays the output from the PA back to the singer, so they can hear themselves. These are wedge shaped and go in front of the singer with the speaker pointing up at their head. We also use ours as the vocal PA in rehearsals. Again, many other makes and fairly easy to find secondhand.

The gear I've referenced here is stuff I've used and it was ok, but you need to find what works for you.

[BOD2]

Just to give you some more terminology ...

A "mixer" has already been defined. It's where all the mics etc, plug into and give you the correct volume "mix"

A "powered mixer" is a mixer with an amplifier built int the same box. It's usually a two-channel amplifier whch means it can drive two sets of speakers (left and right).

A "passive speaker" is a like a PA version of your standard guitar/bass speaker cab. A box with the appropriate speaker type built in. You'll need separate amplifiers to power these.

An "active speaker" is a speaker cabinet with an amplifier built-in to the same cabinet. More expensive and heavier than passive speakers but compact, easy to set up and the amplifier is perfectly matched to the speaker.

A "monitor" is a speaker cab that usually sits on the floor and faces back to the band. It allows the band to hear some of what is being sent out of the PA speakers at the front. The singer will often need this to hear himself.

A "crossover" splits the signal from a mixer into different frequency ranges, which can then be sent to different speaker cabs optimised to handle these ranges (e.g. bass bins, mid cabs, high frequency horns). Sometimes a bass bin willk have a crossover built-in.

The more you look into it the more there is to learn !

[Happy Jack]

Whatever you do, don't get involved in programmed stage lighting ... that makes PA stuff look like playing a kazoo.

[spinynorman]

[quote name='Happy Jack' post='326859' date='Nov 11 2008, 03:36 PM']Whatever you do, don't get involved in programmed stage lighting ... that makes PA stuff look like playing a kazoo.[/quote]



It's also a good idea to avoid becoming the band's PA guru, which is all too easy for bass players to do, due to the staggering technical incompetence of singers, drummers and other band members. From my personal experience ...

- singer, in a hurry to get home, grabs the amp and heads for the door, without unplugging any of the leads.
- keyboard player helpfully plugs both the PA speakers into the line out jacks ...
- and then plugs his awful wireless, feedback-prone mic into the speaker socket.
- singer, waving his mic lead hopefully in the air "Where does this go again?"