What Is The Difference Between A Preamp & A Power Amp? + FAQ

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Both of these sound so similar that confuse many newbies who are learning or looking for separates for home theater. Their functions are also very similar. That’s why I am trying hard to answer it in a way that will be very easy for newbies. So what is the difference between a preamp and a power amp?

At A Glance: The preamp takes a low-level voltage signal and converts it to a higher volts signal, so the amplifier can work on it better. The amplifier further amplifies it and also adds current to the signal so it can power up the speakers. Power is equal to the voltage multiplied by the current.

Keep reading as we will discuss many more aspects and this one aspect too in detail. I have also answered very similar questions like this one in the article. This article will educate you well enough about the preamp and power amps.

Let’s Discuss Other Aspects Of The Difference

PreampPower Amp
Outputs high impedanceOutputs low impedance
It can’t power passive speakers directlyIt can directly power passive speakers
It output high voltage but it can’t be used for speakersIt output enough voltage that can power speakers
It can’t add current to the voltage signal it amplifiesIt amplifies the voltage and also adds current to the signal

Both the preamp and power amplifier are voltage amplifiers but the voltage signals that come out from the preamp are heaving high resistance in other words impedance. The signals themselves are not amplified to the level of voltage that can be enough for the speakers. Also, signals come with high resistance.

The preamp only amplifies its voltage to a level that can be the best fit for a power amplifier to further work on it. The output signal from the preamp ranges from 1.3-4 volts. A 27dB power amplifier will amplify these signals to 29.38-90.4 Volts RMS with added power.

These 90.4 Volts RMS will have a current multiplied with it so it can power up the speakers. Also, it will have the lowest impedance with the signals that can easily power higher impedance speakers without any hassle while preamp signals have a very high impedance that can’t power the lower impedance speakers.

These last sentences can be confusing. So, keep in mind that 2 ohms impedance is required to power up 4, 6, or 8 ohms speakers. The speaker’s impedance means ohms as high as better and the power amplifier signal ohms as low as better.

So, this is the main difference. The preamp signals resistance/impedance/ohms are very high while the amplifier signals impedance is comparatively lower than the speakers. Also, the preamp signals don’t have current while the power amplifier signals have it.

Read my guide about the best preamp/processor for home theater. You will know more about this topic with some exciting features.

What is the purpose of a preamplifier?

In-Short: The preamp takes a lower-level signal and amplifies its voltage to a level that can be easily digestible by the power amplifier. 

In-Depth: A power amplifier requires at least 3 volts of a signal so it can amplify it further properly and can deliver clean signals to speakers. But if there is no preamplifier in the chain then it can’t deliver clean signals the signals will be clipped. We will discuss this furthermore in the preamplifier difference section.

Does a preamplifier make a difference?

In-Short: With a preamplifier, the sound feels more realistic, immersive, natural, fuller, and clean without any level of distortion, and also the speakers last longer than usual.

In-Depth: Why and how does this cool difference preamp bring? Because it delivers digestible signals to the amplifier. The power amplifier can better digest preamp refined signals because now they have a little higher voltage than usual. These signals get delivered to the speakers in a clean form. These speakers can throw a nicer sound without distortion.

But if there is no preamp in the chain then the edges of the incoming signals will be cut and that is called clipped signals. These signals will be amplified but will be delivered in the exact same clipped form to the speakers.

The speakers will produce height due to these clipped signals and will sound distorted at high volumes. Hence the quality of the sound will be worse and the speakers will age faster.

To have a more accurate sound than you must calibrate it with an SPL meter. Click on the SPL mere to know the best ones and the method to calibrate the sound of your home theater.

What is the purpose of a poweramp?

In-Short: The poweramp takes signals from the preamp and amplifies its voltage and adds current to these signals from the power supply and delivers these signals with more watts and less impedance to the speakers. So, the speakers get enough power for their job.

In-Depth: We have discussed these before, that’s why I will close this section with a brief explanation in other simpler words. 

The preamp signals have high impedance and no watts. The power amplifier just lowers the impedance and also adds watts to it so it can drive huge watts speakers easily.

Does a power amp make a difference?

In-Short: AV receivers sometimes can’t power up the speakers in the surround sound enough that’s why they sound distorted or cut out at high volume. Here is why amplifiers come to the action to power up these speakers and they sound better without distortion and cut-out issues.

In-Depth: AV receivers can’t power the speakers when they don’t have enough watts for the speakers. In numbers, when your LCR (front left, center, and front right ) speakers have 85 RMS watts required and the AV receiver is just 80 or 75 RMS power per 3 channels.

Here the amplifier will save the show. You can then power these 3 speakers with an amplifier and the rest will be powered by the AV Receiver.

Now, the speakers will sound better without any distortion and will age like a fine wine.

Know how to match preamp and power amp. It is very important to match them both to work properly. Read my guide about it.

Do I need an amplifier if I have a preamp?

In-Short: To save your speakers from clipping damage and to save the sound from distortion, and unnatural and less realistic signs then you need a preamp. 

In-Depth: The preamp is much needed if you love your sound system and you want it to last longer with you and if you love the immersive sound. By the way, the home theater or any other theater is created to have immersive sound and realism of the movies, music, and games. 

And this immersiveness of the sound can be better defined by the preamp in the chain. That’s why it is needed. 

What is more important, a preamp or a power amp?

In-Short: Important is the power amp, you can drive the surround speakers without a preamp but can’t without a power amp but still, the preamp is required for that fuller and more immersive sound.

In-Depth: Yes, a preamp is indeed an optional component of the home theater but with it, the sound experience is different and completely on another level.

The surround sound speakers can’t be driven without the power amp because they need the power to throw sound like we need food to leave. 

In other easier words, a Power amp is a portion of food to have while a preamp is a yogurt that helps us in better digestion. I think I have ended this debate once and for all.

Know how to optimize the audio of home theater in 5 simple steps. Read my this guide to have the perfect sound.

Did you get something out of this preamp and poweramp guide? Hold On We Have Something Exciting To Share.

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How to use a preamp with an amp?

Many modern preamp/processor for home theater has media source or radio capabilities. You insert a blu-ray into the preamp/process and the preamp XLR outputs are connected to the respective XLR outputs on the amp. 

The amp is then connected to each speaker. And in this way you use a preamp with an amp.

Do power amps have volume control?

The home theater power amps don’t have any volume control on them. They only have options for gain.

The preamp has volume controls. The volume can be controlled by the preamp and the gain can be controlled by the amplifier.

Can a preamp drive a speaker?

It can drive a speaker when a speaker has a built-in amplifier in it. Meaning it is an active speaker that is self-powered. To these types of speakers, you can directly attach the preamp without having an amplifier in the chain.

Helpful Resources For The FAQs To Read More

  1. Read more about it on TechWalla. (Resource for the first answer)
  2. This was my opinion, read more here on SteveHoffman Forum. (Resource for the third answer)

Watch To Learn More

This article was first posted on Homelytainment.com.
Ayaan Khan
Ayaan Khan

I'm Ayaan khan, a freelancer and a Computer Science degree holder from P.E.S. College. After my degree, I started an internship with my father in his home theater showroom. After working for a month I realized that this is the best job in the world for me and it could be turned into a passion. Fast forward to when my internship ended, I joined my father as a full-time home theater equipment tester. I test new equipment and approve it before it can be installed in the customer's house. I love to test equipment and sometimes love to install it by myself in the customer's theater room. I have the right experience and knowledge to learn from my articles. In my Free time I write & answer questions here on AVSFORUM. Every Article on Homelytainment is curated according to Homelytainment's Editorial Policy and Sponsorship Policy. If you have any questions for me. Reach out to my email (Support(AT)homelytainment.com)

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