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Pro audio power amplifiers buying guide

How to choose a power amplifier that's right for you

The power amplifier receives the audio signal from the mixing board or signal processor and magnifies it, giving it the power it needs to drive your speakers and entertain your audience. In this article, we'll discuss the things you need to know when choosing an amplifier for your pro audio system.

Crown amplifier stack

The amplifier is the heart of a pro audio sound system, providing the power that speakers need to create music.

What to look for in an amplifier

Most amplifiers have similar features. The differences come in the amount power it produces, the number of channels it has, the types of connections it offers, how the controls are set up, and whether it has any built-in processing or effects.

How much power do I need?

This can feel like a bit of a minefield since amplifiers and speakers will often come with multiple power ratings. For best results, pay attention to the amplifier's RMS power rating. That's a measure of how much power it puts out consistently.

Speakers, on the other hand, tend to list a program power rating for their handling capabilities. This is the amount of power a speaker needs in real-world situations.

Compare the amplifier's RMS power rating (how much power it puts out consistently) to the speakers' program power handling (how much power the speakers need to sound good).

  • As a general rule, the amplifier should be able to provide up to twice the speaker’s program power rating.
  • Also important to note is that it’s generally better to overpower a speaker a little than to underpower it. It is much easier to damage a speaker by giving it too little power than by giving too much.

For example, for a speaker with a program rating of 200 watts, you want an amplifier that'll deliver between 200-400 watts RMS. The closer you get to the higher number, the better the speaker will sound.

Other power ratings

The peak power rating gives you an idea of the maximum, instantaneous short-term power an amplifier can deliver or that a speaker can handle, typically for intervals lasting less than a second. 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) load of the speakers it's driving. It'll put out different amounts of power to different impedance loads. So you might see something like an amp that’s rated 1,000 watts at 8 ohms, but 1,500 watts at 4 ohms.

Problems arise when the amp's output meets very little resistance (low impedance) and it tries to put out more power than it was designed to produce. This leads to the amplifier overheating and shutting down — not good in the middle of a performance. In most cases, power amplifiers are rated to work best against 4- or 8-ohm loads.

Just remember that the amplifier you choose must be able to provide an adequate amount of power to your speakers at the impedance they present to the amp's output. For example, connecting two 8-ohm speakers to one channel presents the amp with a 4-ohm load. Make sure the amplifier can handle that load before adding the second speaker. In this case, there's no problem.

Using our example above, our amp puts out 1,500 watts at 4 ohms. This power is divided among the two speakers, so each will get 750 watts. If that's enough power for the speakers, then this amp will be a good match for them.

How many channels do I need?

Power amplifiers are categorized by the number of channels they offer: mono (single-channel), stereo (2-channel), and multi-channel (usually 4). The vast majority of amps are 2-channel. They're the most popular because of their flexibility. You can use one as a 2-channel stereo amp, two single-channel amps, or a more powerful, single-output amp.

How many channels you need depends on how many speakers you need to power. A simple system with two speakers (left and right) is perfect for a 2-channel amp. If the amp has enough power, you can add more speakers on each channel, so long as the impedance load we talked about doesn't drop too low.

And that leads us into...

Stereo, parallel, and bridged modes

Most amplifiers can be operated in stereo or bridged modes, which determine how they’ll handle the signals. Some amplifiers also offer a parallel mode (sometimes referred to as parallel mono).

Stereo mode

Stereo is the default mode for 2-channel amplifiers, and is used for powering a pair of speakers, one right and one left. In stereo mode, each channel is receiving a signal independent of the other. A 2-channel amp in stereo mode can also be considered the equivalent of two mono amplifiers — for example, one channel can power PA speakers while the other powers the stage monitors.

Amp wired in stereo mode

Parallel mode

Parallel mode allows a single input signal to be sent to both channels, and the second input channel is not used at all. This can be used to route a mono input such as a microphone or mono output from a mixer into both channels of an amplifier. This mode can be useful when powering an odd number of speakers. If you want to use three speakers, using your amp in parallel mode would send the same signal to all three speakers.

Amp wired in parallel mode

Bridged mode

Bridged mode combines the power of both channels, sending more power to a single output. In many cases the output power may be more than double the amplifier’s normal power rating. This mode is typically used to send a signal to a subwoofer. In most cases, the impedance of the speaker should be double the minimum impedance of the amplifier in stereo mode. It’s important to note that the manufacturer’s instructions should be followed when bridging an amplifier, which may involve using a “jumper” cable or connection between the output channels on the back of the amplifier.

Amp wired in bridged mode


Headroom is a term that gets bandied about quite a bit when discussing power amplifiers, and it's the reason everyone suggests having more than just enough power to satisfy the RMS requirements of your speakers. Having that extra power gives you several benefits: 

  • It lets you turn up the amp without distorting the music on those occasions when you need to play louder than usual, like when your band is playing a larger venue than normal.
  • It allows you to play music with a wide dynamic range (music that has quiet parts and loud parts) and have those loud parts sound just as good as the quiet parts.
  • When that bass hit drops or that high note screams, the headroom in your system keeps them both clear and free of distortion.

Having lots of headroom helps you avoid...


Clipping of an amplifier occurs when you try to get a larger output signal out of an amplifier than it was designed to provide. This is a fancy way of saying that your amp doesn't have enough headroom. It usually happens when an amplifier is already performing near maximum power output and the volume is increased sharply. The tops (and sometimes the bottoms) of the signal waveform are cut off (or “clipped”), resulting in a highly compressed signal that results in distortion, which can damage your speakers.

Power amplifiers have indicator lights to warn you when the signal is approaching the clipping point. These tiny lights have saved many a speaker.

Heat and distortion

So what happens when you don’t stay within the recommended parameters? Typically you’ll introduce heat and distortion into the signal path, and those are both enemies of good sound. Heat can build up within your amplifier’s internal circuits, causing a shutdown or — even worse — a meltdown. Distortion is caused by heat and irregular sound waves, and it’s bad for both your speakers and your listeners’ ears.

Input and output connections

Power amplifiers typically offer XLR and 1/4" inputs for your incoming audio sources. You’ll need to keep an eye on your amplifier’s output level when switching between sources using different inputs because XLR inputs are much lower in voltage than 1/4" jacks. If you can help it, avoid using two different kinds of connectors when plugging into a power amplifier.

Crown XLS amplifier outputs

This output panel has both locking outputs and binding posts


Amp outputs will usually be a combination of Neutrik SpeakON, banana/binding posts, and 1/4" outputs. SpeakON plugs offer the added security of a twist-and-lock connection, while banana/binding plugs are more versatile. Banana/binding plugs can also accept bare wires if the need arises. 1/4" plugs connect to cables that can be confused with instrument or patch cables, which is less than ideal because instrument or patch cables are not designed to carry amplified audio signals. 1/4" plugs can also short out if they are touched to metal. Be sure to check which types connections your speakers accept when shopping for an amplifier and cables.


Most amplifiers feature very basic controls. 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 or when thermal compression or other signs of overheating have begun. In many cases, there will also be a light signaling the amp’s entry into protection mode, which is automatic shutdown to protect the amp’s interior circuitry. Some amps may have a small LCD screen that provides status updates or can be used to set crossovers, amp mode, and limiter configurations. Switches for stereo, parallel, and bridged modes will often be found on the rear of the amplifier.

Front of Crown XLS2000 power amplifier

The LCD display on this Crown amplifier helps you dial in the settings

Filters and crossovers

Some amplifiers offer a high-pass filter, also known as a low-cut filter. This lets you reduce the output of a speaker below a certain frequency (typically between 20 and 150 Hz). 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, and is also helpful when you have a separate subwoofer handling the bass in your PA system.

Amplifiers can also offer more sophisticated crossovers, which are filters that divide the incoming signal into multiple frequency ranges. These are especially handy for multi-speaker setups or for systems which involve a subwoofer. With a crossover network, you can dictate which frequencies go to which speakers, maximizing the efficiency of your amplifier’s power by ensuring it won’t work harder to power speakers that have a difficulty reproducing certain high or low frequencies.


Limiters are protection circuits that can help keep your amplifier from clipping and to prevent distortion in the sound. A limiter lets you set a maximum level setting and prevents a signal from going above it. Limiters help prevent distortion caused by an overdriven signal, a dropped microphone, or a short in an input jack.

Getting the most out of your power amplifier

Connections and cabling

Improper connections can result in unwanted noise or interference, so be sure to follow your amplifier’s owner’s manual regarding plugs and cables. This is especially true regarding balanced and unbalanced connectors — see our guide to choosing the right cables.

  • Most amplifier manufacturers recommend using balanced connections throughout the signal path, which will insure the least amount of outside interference.
  • Whenever possible, avoid power strips and try to plug your power amplifiers directly into an AC outlet or power conditioner.
  • A good rule of thumb for speaker cable is the shorter, the better. Use the same length of wire for each speaker connection, even if one speaker is closer to the amplifier.

Avoid overheating and distortion

Once everything in your sound rig is properly connected, the amplifier should be the last thing you turn on, and the first thing you turn off when it’s time to shut down. When trying to find the best point to set the levels (gain) for your amplifier, make sure you listen closely for distortion and pay attention to the amp signal levels for clipping. If you see indications of clipping or hear the sound distorting, dial the levels back.

Multi-speaker setups

When attempting to send audio through multiple speakers at the same time, be sure to consider the advantages and disadvantages of using multiple amplifiers, or even a multi-channel amplifier. Look at the impedance load implications of wiring multiple speakers to an individual channel, and determine whether one amplifier is up to the task. If you want more than two speakers in your system, it's often best to add another amplifier. And subwoofers almost always need their own amplifier.

When dealing with a subwoofer, you’ll find that using your amp's crossovers can make a big difference in the sound. The crossover lets you send the low frequencies to the subwoofer and the middle and high frequencies to the main speakers. External (or "active") crossover networks are great for single or multi-amp systems because they are efficient and have a wide dynamic range. In the signal chain, external  crossovers are usually found between the mixer and the power amplifier. You can separate signals into high-, low-, and sometimes even mid-frequency bands and send to the proper speaker for optimum response.

The right amplifier for you

Matching an amplifier to your speakers is an important step, but it's just one of several on the road to great sound. Our experts are here to help walk you through the gear, so don't hesitate to give us a call if you have any questions. We can assist you in choosing the gear you need for a great sounding system.

When you purchase your PA gear from Crutchfield, you get access to our free lifetime tech support. We can advise you on the best ways to set up your PA system so you can enjoy memorable live events at the club, church, auditorium, or wherever you like.

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 .?