#1November 10th, 2008 · 07:24 PM
2 threads
1 posts
United States Minor Outlying Islands
power amps
What are power amps and how are they used?
#2November 10th, 2008 · 07:42 PM
160 threads / 33 songs
1,965 posts
United States of America
I was gonna send you to Wiki.. but really it is nothing more than the signal booster in the last stage before the speakers (audio). It takes input signals and attenuates the signal upwards in strength (gain).  Now for audio (P.A., studio monitors,or stereos,) you have stand alone power amps that you buy separate , usually hood your output of your receiver , mixer, audio interface, pre amplifier, in to the input , then speakers to the output.  Now days we have speaker cabinets with the amps built inside of them. Self powered speakers .. they can be studio monitors, P.A. speakers, audio speakers. They have the power amps built in to them.. I tried to use a very basic explanation for this. i hope this helps some

#3November 10th, 2008 · 09:38 PM
28 threads / 20 songs
255 posts
Australia
From your previous question 'what is RMS wattage?' to 'what are power amps' - I take it that you might be interested in PA speakers or something similar. Cut me off if im wrong but ill assume your talking in the context of PA speakers or 'live sound'. Power amp is basically an amplifier without the speakers (in the context that we call it a guitar amp - but really it's a guitar amp and speaker). If you buy PA speakers that are 'active' they have the power amp built into them and all you need to do is plug a microphone or something into them and you can get a nice loud sound. If the PA speakers are 'passive', they do not have any sort of amplifier in them, they will usually just have an input and a horn/woofer/tweeter. Now if you want to know quickly if the speaker is active of passive, passive speakers usually (from what ive seen) don't need power. ie. dont need to plug them into the power socket. ie dont have a power cable. Active speakers do because an amplifier needs current from the powerpoint to operate.

Now for passive speakers, they dont have an amplifier, so you usually buy a power amp (what you were asking about) to power it. This Power amp will usually only have a stereo input and stereo output and will have a certain RMS Wattage output for each mono output (the amount of power it can output). Now to plug in multiple instruments into a power amp or to have effects etc. you will need to first run everything through a mixer  like toasted goat was saying.

What i am trying to get at is you can buy a 'power mixer' - thats right, it's a mixer with an amplifier in it so you dont have to have a separate mixer and amp.

So there are all or most of the options.

I PERSONALLY have a powered mixer and passive speaker set up. I much rather prefer having passive speakers and an outboard powered mixer because then the speakers DONT WEIGH a tonne. FACT 1: Amplifiers weigh A LOT! (especially 500W+ ones, yes in general the more power they output the more they weigh). FACT 2: Speakers can weigh a lot as well, especially your 1000W capacity speaker with an 18" horn. Now as i said a active speaker combines both amp and speaker into one... therefore total weight = amplifier and speaker = much more than a passive speaker which is just the speaker.

When your gigging every week, any weight reduction is a relief, even if it means a little bit more things, atleast putting up two passive PA speakers on 8 foot high stands every week will only give you severe back problems in 10 years rather than the next morning, as it is with lifting active speakers.

The problem is with passive speakers and power amps, that you have to get the impedence/resistance, power capacity, and power output matched between the speakers and the amp matching or else you can suffer bad quality sound, distortion or even blow your tweeters or woofer. (ive personally replaced both tweeters on my Pa's twice already). Active speakers are already pre-installed with all the right impedence and power input/outputs so you dont have to worry about it.

So there you have it, Power Amplifiers and Speakers 101.



So in terms of PA speakers, the two decisions you can make are either active or passive. I much prefer buying passive speakers
#4November 11th, 2008 · 07:50 AM
55 threads / 30 songs
1,558 posts
United Kingdom
Toasted Goat has it for simple explanations for me... while Chill has the detail.

Audio power amp = a device to increase the power (volume) of an audio signal.

How are they used? In conjunction with other audio equipment (see TG's diagram above) they are the last part in an audio chain before the output device, which are usually speakers.
Typical example: take a weak signal from a microphone, add equalization and effects using a mixer/pre-amp and effects processor, send the combined signal to an audio power amp, and send this to the speaker.  The result is a boosted signal from the microphone - the actual volume is dependent on every part of the audio chain.

And as a complete opposite of Chill - I've chosen to use active speakers (so speakers with a built in amp) rather than a separate power amp, because I like them... but yes, they are heavy!
#5November 13th, 2008 · 10:04 PM
37 threads / 25 songs
237 posts
United States of America
POWER AMP
ITS AN OLD MESA  BOOGIE!
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