View Full Version : What is a PA?!
JAM8086
12-05-2003, 10:10 PM
hey - im new to the forum and i am a huge fan of DT/LTE and Jordan Rudess, of course. I was just wondering what the purpose of a power amp is. Im talking about something like this - http://peavey.com/products/shop_online/browse.cfm/action/details/item/00324800/wc/2A2C2/fam/2C/tcode/2/s.cfm
I've been looking at the Peavey Kb5, which JR uses, and it says it has a built in PA, so my main question, besides what the purpose of a PA is, is what is the difference between an amp without a PA and an amp with a PA. Thanks!
Welcome to the board 8)
PA stands for Power Amplifier (in this case). Most audio equipment (keyboards, mixer, cd-player...) has line output', that means the audio signal coming out has a specific amplitude (know something about physics?). It hasn't got enough power to be directly connected to a speaker, but it's easier to handle if it's less powerful. So to bring this low signal to a speaker you have to give it more power, you have to amplify it, and that's what a power amplifier does.
It has an input and an output, you put in the low signal from your keyboard into it and get a high signal for speakers out of it - that's why for example you need other kinds of cable after that, because the signal is much higher. The height of this second signal depends on the power of your amplifier, it's give to you in 'Watts'.
(BTW: microphones and guitars cannot be plugged directly into an amplifier, their signal is lower than a line-signal and has to have another preamp before going into the power amp).
The Peavy you talked about has speakers and a power amp built in, so you can directly plug your keyboard into it and have your sound. If it hasn't amplification you need an extra power amp between your keyboard (or cd-player, mixer ... of course) and your speakers. Keyboard ampsusually have an amplifier built in, while guitar-amps are also available with single speakers and a top, which includes the power amp.
Hope I could explain the basics without having all the words I needed in english ;-)
PA actually refers to Public Announcement or Public Address system. No? :lol:
Angelic Layer
12-06-2003, 09:43 AM
PA stands for public addressing system.
It refers to the whole system, not only the power amp.
Kamin
12-06-2003, 04:34 PM
is that the same thing as balanced and unbalanced or is that totally different, cuz that makes no sense to me, then i havent really done much research.
Spacehog
12-06-2003, 04:53 PM
Balanced and unbalanced is to do with the type of connection. An unbalanced connection / lead, such as a guitar lead, has a single signal connection (the pin) and a ground (the sleeve). A balanced connection (such as a microphone cable) has a +ve signal (pin 3 on XLR / Tip on a TRS jack), a -ve signal (pin 2 on XLR / Ring on TRS jack) and a ground (the sleeve)
Balanced connections are generally better because they are much less susceptible to interference. The reason is, with the signal going down two wires that are inverted, any interference will cancel itself out when the -ve signal is inverted and mixed with the +ve one in the preamp.
Certain leads are always unbalanced (guitar leads, most insert leads, cheap patchbays), certain leads are always balanced (mic leads, most things with XLR connectors, particularly if they have to carry phantom poiwer - you MUST not send phantom power down an unbalanced line!), and some, such as keyboards etc, can be either, depending on the keyboard. If your keyboard isn't balanced, and you have to set up near any lighting, then get a DI box and run balanced leads to the desk - keep your unbalanced leads as short as physically possible!
Martin
I actually invented a balanced/ unbalanced guitar,
for a while I liked that it gave me a nice clean sound but it wasn't very good for distorted tones.
No troubles sending phantom power to passive balanced devices.
(There isn't a individual phantom power switch for each input on any mixers that I've seen)
http://www.evl.uic.edu/tomk/data/evl-audio/presentation/images/bal_unbal.jpg
drumguy1384
12-06-2003, 10:24 PM
Yes, generally PA stands for "Public Address", but in this case it also stands for "Power Amplifier" ... such is the fate of acronyms.
To put it succintly, a keyboard with "built in PA" is one with a built in power amplifier ... capable of plugging into a separate speaker for amplification purposes.
On the other hand, a PA is usually considered to be the "house system" ... or whatever mixes and amplifies everything for a gig/concert performance. In this case it is the "Public Adress" system that controls everything.
Of course, the "Pubilc adress" system also incorporates "Power Amplifiers" ... which is what causes the acronyms to be confused.
-- Drumguy1384
Spacehog
12-07-2003, 03:28 AM
I'd assumed, rightly or wrongly, that the Peavey amp incorporates a "PA" because it includes a mic preamp and some kind of built in reverb/effects. A keyboard amp without a power amplifier would be absolutely useless, so that's hardly a feature!
I've never come across PA referring to power amplifier, despite having come across a lot of different meanings for it!
Martin
Other acronyms for P.A.
per annum.
power of attorney
press agent
production assistant
prosecuting attorney
I as well never heard a Power Amp getting the P.A. acronym :roll: :wink:
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