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PA amplifiers buying guide

How to choose a professional-grade power amplifier for your PA system

Professional-grade audio amplifiers are designed for use in PA (public address) systems. Their job is simple: Take the audio signal from a mixing board and magnify it. Then they send that amplified signal to a speaker or a set of speakers.

PA amplifiers can withstand harsh operating conditions and a certain degree of unintended abuse. Most models have robust protection circuits, trouble-sensing signal limiters, and other safeguards. When pushed too hard, they protect themselves, save your speakers, and prevent audible distortion.

PA amps installed at a bar.

We recommended two Crown amps for a local nightclub's PA system

Pro amps are versatile, too. That means they can safely adapt to a variety of speaker system configurations. Models with digital signal processing (DSP) let you tailor the amp’s output to suit your speakers and the space they’re in.

In this article, we'll discuss the things you need to know when choosing an amplifier for your PA system:

Where to start

Before you start shopping for amps, sketch out a system plan. The planning process starts with a few basic questions:

  • What’s the size and nature of the space or spaces you need to cover with sound?
  • How many and what kinds of speakers will you need to meet your coverage needs?
  • How loud will your sound need to be?

Scratching your head already? Chat with one of Crutchfield’s experts. Your advisor will help you come up with a solid system plan. But please finish reading this article first. You’ll be better prepared for the conversation.

How many amps (or amp channels) do you need?

You may have noticed that power amplifiers have different numbers of channels. A channel corresponds to a single set of speaker connections – one positive connector and one negative connector.

PA diagram

Use a 2-channel amp for a simple, two-speaker system.

PA diagram

Here's a more complex system that uses four amps — a 2-channel amp for the main speakers, another 2-channel amp for the stage monitors, and a 2-channel amp in bridged mode for each of the two subwoofers.

Say you want to power two “main” speakers, one on each side of a stage. The obvious choice is a 2-channel amp.

You might want a second 2-channel amp to power two “monitor” speakers. The monitors are the wedge-shaped speakers that sit on the stage floor and fire sound up toward the performers.

If your audience likes a lot of bass, your system should include or more subwoofers. You can use a 2-channel amp in “bridged” (1-channel) mode to power a subwoofer. Bridged mode combines the power of both channels, sending more power to a single output.

Bridged mode hookup diagram

Bridged mono mode wiring for a subwoofer.

We also offer a few 4-channel amps, which are good for a variety of system configurations. They can also help you save space.

For more information about system configurations, read our intro to live sound equipment.       

How much power do you need?

PA speakers have a program power rating and a continuous power rating.

The continuous power rating is typically half of the program power rating. Think of it as the minimum amount of power a speaker needs in real-world situations. You want an amp that provides at least that much power. But you can safely use an amp with up to twice as much power.

For example, for a speaker with a continuous power rating of 200 watts, you want an amplifier that delivers between 200 and 400 watts RMS. The closer you get to the higher number, the better the speaker will sound.

A peak power rating gives you an idea of the maximum, instantaneous short-term power a PA amplifier can deliver or that a speaker can handle. It’s good to know, but not very helpful when planning a system.

Amplifier power and resistance

The amount of power an amplifier generates depends on the impedance (or resistance) of the speakers it's driving. It'll put out different amounts of power to different impedance loads. So you might see an amp that puts out 1,000 watts at 8 ohms and 1,500 watts at 4 ohms.

Keep this in mind when you’re shopping for speakers. Most PA speakers are 8 ohms. Choose 4-ohm speakers like the JBL PRX425, and you’ll get more power out of your amp.

But there’s another way to maximize the amp’s potential. Just add more speakers!

Two main speakers facing your crowd is a good place to start. But four speakers will spread the sound around your space more evenly.

Do you have to buy another amp for the second pair of speakers?

Not necessarily. You can connect two speakers to the amp’s left channel and two to the right channel.

Speaker hookup diagram

Connecting two 8-ohm speakers in parallel presents the amp channel with a 4-ohm load.

When two speakers are connected (in parallel) to one channel, the channel’s power is split between the two speakers. Say your amp puts out 1,500 watts at 4 ohms. Connect two 8-ohm speakers in parallel, and each one gets 750 watts. Make sure you choose speakers that can handle 750 watts.

Amp classes

When shopping for PA amps, you may notice that they come in different classes. The class designations tell you something about the design of their output stages, but you probably don’t need know all the details. What do you need to know?

Most of the amps we offer are Class D. This is the most efficient class of amplifier. Class D amps are much lighter and run cooler than other types.

We offer a few Class AB amps, and – at least in theory – they deliver better sound. In most live sound situations, however, you are unlikely to hear the difference.

Dance club DJ booth

You'll need a system with lots of headroom for a crowded dance club.

Headroom

“Headroom” is a term that sound pros use a lot. A system with good headroom has all the power the speakers can handle, not just the bare minimum they need to get by. Headroom gives you several benefits: 

You’ll have power in reserve, which will come in handy when your band hits it big. You won’t have to buy new gear to play in larger venues.

Your system will have better dynamic range. The loud parts will sound just as good as the quiet parts.

The bass parts will hit a lot harder without distorting.

“Clipping” distortion occurs when you push the limits of an amp that doesn't have enough headroom. The tops and bottoms of the signal waveforms are cut off (or “clipped”).

Clipping can damage your speakers. Some PA amplifiers have indicator lights to warn you when the signal is approaching the clipping point. These tiny lights have saved many a speaker.

What you need to know about the connections

Power amplifiers typically offer XLR and 1/4" inputs for connection to a mixing board or other audio source component.

Most amplifier manufacturers recommend using balanced XLR connections throughout the signal path. Balanced connections reject noise. They’re especially helpful where long cable runs are necessary.

You may also find RCA connections, which are more common on home audio components. That begs the question: Can you use a pro amp in a home audio or home theater system?

You’ll typically get more watts per dollar with a pro amp than you will with an amp designed for home use. That’s why we sell a lot of Crown amps for home theater systems. There are few things you need to know before you go down this path.

This might go without saying, but your home theater receiver must have multi-channel preamp outputs. (Or you could use a preamp/processor instead of a receiver.)

The pro amps you have your eye on may not have the right kind of input jacks. (Yes, you can get adapters to solve this problem.)

Pro amps have cooling fans that are noisy enough to be heard during quiet scenes in a movie. So you may want to locate the amps out of earshot. Or isolate them in a cabinet. Just make sure the cabinet is well ventilated.

Pro amps have input gain settings (and some other adjustments) that may bewilder a home user.

You have to be careful where you place the amp. Some pro amps have a strong magnetic field that can induce hum into other nearby components.

Finally, most pro amplifiers do not have 12-volt triggers, or input-sensing auto turn-on circuits. This means they won't power up when you turn on your receiver or preamp/processor. You either leave your pro amps on all the time or manually turn them all on each time you want to watch a movie. 

Speaker connections

There a three different kinds of amp output jacks.

  • Neutrik SpeakON
  • Banana/binding posts
  • 1/4" TS (Tip/Shield)
speaker jack types

Speaker connection options — A) SpeakON, B) Banana/binding posts, C) 1/4"

SpeakON plugs offer the added security of a twist-and-lock connection.

Banana/binding plugs are more versatile. They accept bare wires, if the need arises.

When using 1/4" connections, make sure you use pro speaker cables with 1/4" plugs. Don’t use instrument cables, which have the same kind of plug, but aren’t designed to carry amplified audio signals.

Preamp outputs

Planning to use multiple amps in the same system? You’ll need amps that have preamp-level “link” outputs. They sends the mixing board’s signal on to the next amp in the chain.

All about the knobs, buttons, lights, and display screens

Some PA amps are pretty brainy. You may find knobs, buttons, and indicators for the following:

Gain settings

Typically, the front of the amplifier will have a gain/level knob and signal level indicator for each channel. Colored lights indicate when the amp is clipping. Proper "gain staging" starts with the settings on your mixer. To learn more about the process of setting levels at each link in your audio chain, read this article.

Frequency filters

Frequency filters let you tailor the output of an amp to suit the type of speakers it’s driving.

A high-pass filter (also known as a low-cut filter) lets you reduce the output of a speaker below a certain frequency. It lets the amp focus its power on the higher frequencies and not waste energy on the power-hungry bass frequencies.

This kind of filter helps to eliminate audio distractions such as bass rumble, wind noise, and microphone thumps. When you have a separate subwoofer handling the bass in your PA system, you’ll want to remove the deep bass from your main speakers. They’ll play louder without distortion.

A low-pass filter removes the high-frequencies from the amp’s output. Use the low-pass filter when the amp is driving a subwoofer.

A band-pass filter removes both lows and highs. Band-pass filters are good for fine-tuning the performance of your subwoofers.

Limiters

Limiters are protection circuits that can help keep your amplifier from clipping and to prevent distortion in the sound. They help prevent distortion caused by an overdriven signal, a dropped microphone, or a short in an input jack. 

Time alignment

Churches and theaters often have speakers along the side walls. These allow people in the middle and the back of the room to hear things just as well as the people up front. And you don’t have to turn the front speakers up too loud.

For your side speakers, you’ll need an amp with the ability to delay the output signal. A little delay will “time-align” the side speakers with the front speakers. The sound remains crisp and highly intelligible throughout the room.

Parametric EQ

Some amps have very sophisticated equalization capabilities to help you fine-tune your sound. These adjustments can be made via the front-panel buttons or (in some cases) with a connected computer. Features like this eliminate the need for racks full of outboard signal processors.

Hands-on demos of amp settings

Here are a couple of videos that walk you through amp settings. In the first one, our expert Rob looks at the settings on a Crown amp

In the next one, Rob shows you what you can do with the settings on a Yamaha amp.

Questions?

Experts like Rob are here to help you design your PA system and choose the right amps. Call 800-555-9369.

Last updated 8/10/2020

Please share your thoughts below.

  • Larry from Bellingham

    Posted on 10/6/2019

    I just had the owner of a historic building, small to medium venue, call me about updating his audio system. He seemed to be interested in a completely wireless system. If that a possible is it a wise way to go. I'll wait for your response before proceeding with upgrades. Thank you in advance, Larry

    Dominic DeVito from Crutchfield

    on 10/7/2019

    Hi Larry - Thanks for your question. We're hesitant to recommend trying to go "completely wireless" for any sort of PA system, because you're surely going to run into interference issues from cell phones and/or nearby Wi-Fi networks. An advisor should be in touch with you shortly to help you figure out the best system for your needs, or you can reach out to one via email, web chat, or phone.
  • David from Minneapolis

    Posted on 6/9/2019

    Hi, I'm looking for a 2 channel recommendation to power 4 - Martin Logan Motion 4i speakers at the same time and 1 -2 subwoofers (hoping to get away with only 1). The only device hooked up will be a sonos zone player and this will be for music only. Thanks!

    Dominic DeVito from Crutchfield

    on 6/10/2019

    Hi David: Thanks for your inquiry. There's a bit more we need to know about your system before making any recommendations, so one of our advisors will be in contact with you shortly to make sure you get the right gear for your needs.
  • Antony

    Posted on 3/28/2019

    i need to power 10 speakers all at once for my church 6 are of one type and the other 4 are of another type. should i just get 2 smaller duel channel amps to run them duel channel putting 3 in parallel on the 6 set and the set of 4 as 2 parallel or is there anything out there to run 10 speakers

    Dominic DeVito from Crutchfield

    on 3/29/2019

    Hi Antony - Without knowing what kind of speakers you have, I'm hestiant to give any advice here. An Advisor will be in touch with you via email to discuss what your options are for your system.
  • John Donohue from Highlands ranch co

    Posted on 9/9/2018

    I have a 4 zone system with the mains going to run off zone 1 on a marantz receiver. I want to use the 2nd zone preouts to drive an amp for the other 3 zones. The other zones have speakers that are 75 to 60w rms and higher for peak above 240w or so. The speaker wire runs are long tho at 34 to 77 ft. Would the xls 1002 be appropriate to drive that with a speaker selector in line? Or would another amp be better?

    Dominic DeVito from Crutchfield

    on 9/10/2018

    Hi John: It's unclear what sort of system this is — if it's a 120-volt audio application, and you're using a Marantz home audio receiver for the first zone, the Crown amp seems like 1) a bit of overkill as far as wattage and 2) an odd choice if fidelity is your primary concern. There are too many variables to answer this question, so an Advisor will be in touch with you soon to try to find the right solution for your needs.
  • Dominic DeVito from Crutchfield

    Posted on 7/19/2017

    Hi Bill - You definitely do not want to run amp 1 into amp 2. You'll want to connect each Crown amp to one of the bass cabinets. But that Crown amp should be sending 300 watts in stereo mode to each of those Kustom cabs, so before you go to all the trouble of running two amps, make sure that your two cabs are firing together in phase. If they are not, you'll be losing some serious bass. One other issue: the Crown is stable at 8 ohms in bridged mode, so if the Kustom cab is 4 ohms, you do not want to run a single cab with the Crown amp.

  • Bill Corbridge from College Station

    Posted on 7/16/2017

    Great article, but although you showed the multiple amps in a picture, I don't see a discussion of how to connect multiple amps together. For example I have a Crown 402 and two Kustom 215 speakers. It seems that this setup is a bit under powered, so I would like to add a second Crown 402 amp. Do I connect amp 1 to amp 2 and feed the speakers from amp 2, or do I have each amp power each speaker (or some other setup?). Thanks

  • olufemi from lagos

    Posted on 3/30/2017

    Great article.

  • Victor Lee from Kuala Lumpur

    Posted on 1/10/2017

    If the speaker having 400W continuous and 800W program power at 8Ohm and it's looped to a 100W continuous 200W program power at 8Ohm. I could calculate that it requires 1600W and 600W RMS power individually without looping buthow much amplifier RMS power is required when looped as the total impedance is dropped by half? Appreciate the advise. Thanks in advance.

  • Joel Hawk from San Diego

    Posted on 11/23/2016

    I have 10 ceiling speakers in my home. The Speaker craft amp blew out after 10 years. A new one (with individual room controls) cost $5k. I don't need that feature and want to wire all the speakers to one amp. What amp should I purchase and is there other equipment I might needm

  • Alexander Hrabe from Crutchfield

    Posted on 3/15/2016

    Nancy, I've passed your question along to our sales team. An advisor will contact you soon to help find the right amp for your system.

  • Nancy from Charlottesville

    Posted on 3/14/2016

    I am looking for an amp to power my two Klipsch RB-51 II Bookshelf speakers. The specs for these speakers are as follows. Power Handling: 75 W RMS/300 W Peak Nominal Impedance: 8 ohms compatible Would you recommend the rating of an amp that fits this set? Would Crown XLS 1002 shown on your website work? Thank you!

  • Alexander Hrabe from Crutchfield

    Posted on 6/12/2015

    Manoj, since you've already purchased the speakers, you'll want to make sure that the amplifier isn't too powerful for what you already have. You've listed the power output from the receiver, but what you need to look for is the RMS power-handling of the speakers. Based on the Pioneer package you've described, we're guessing that a 4-channel amp, rated between 45 watts and 75 watts RMS per channel, will probably work for you. But double-checking your speaker specs wouldn't be a bad idea before you make a big purchase.

  • manoj from Singapore

    Posted on 6/12/2015

    I am going to fit a Pioneer Car Stereo Audio Combo Pack 4 Speakers + AUX Cable AM FM CD MP3 PLAYER INPUT 200 WATTS DXT-X2769UI00 my car, below is the ratings got for the above model for your close analysis Built-in MOSFET 50W x 4 max power, Amplifier 22W x 4 RMS power Can you advise what could be the best amplifier that best for this set (Is it fine , also the best sub woofer power rating .?