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Power Amp vs Preamp — Key Differences Explained

If you’re a newbie to music and recording, it can be very easy to get drowned in all the information that is suddenly thrown at you, which can bog you down and stall your progress.

Power Amp vs Preamp

Sometimes, you’ll come across two different pieces of gear which may seem similar or almost the same at the beginning but actually play different roles and work in different ways. One such source of confusion is the distinction between power amps and preamps. 

Also read: Receiver vs. Amplifier vs. Preamp – Key Differences

Power Amp vs Preamp – Basic Difference

A power amp is at the end of your recording chain, and its purpose is to increase the volume of the sound that goes into your speakers. On the other hand, a preamp is at the beginning of the recording chain, and it serves to boost weak signals that come from your microphone or instrument before they go further. 

This difference may seem a bit too technical, especially if you are a beginner, so hang around while we plunge into the differences between these two types of amplifiers. We’ll take a look at both and see what exactly they do, so you can compare them and analyze the differences. 

What Is a Power Amp?

A power amp is an amplifier that boosts the signal coming from your input to a high enough level to be transmitted through your speakers or headphones. Ideally, it should drive the signal directly to the output without any changes in the sound. 

power amp
power amp

As the name suggests, a power amp is there to supply power to your speakers. Its job is to further boost the pre-amplified signal coming from the beginning of your recording/amplifier chain and bring it to a high enough volume for your speakers to process. 

The only control there usually is on a power amp is the gain knob (apart from the on/off switch, of course). Gain dictates how loud your sound is going to be. You’re not going to see a detailed EQ on your power amp.

That should also be the only thing your power amp does. A quality power amp should not make any changes to your sound. It should not make it warmer or alter it in any way, at least not significantly. Most changes to your sound should be made before the signal reaches it. 

Once you have fiddled with your sound enough and you’ve got it set to your liking, your power amp is only supposed to amplify it—that is, make it louder, so you can actually listen to it. Of course, some lower-quality power amps may influence your sound a bit too much, but generally, they’re not supposed to do that. 

Do I Need a Power Amp?

You need a power amp for playing music and other types of audio, as well as for recording it. Otherwise, the signal from the input would be unusable, as there would be nothing to boost it to an acceptable level. 

You might be wondering then how your audio equipment generally works without a dedicated preamp. The thing is, in most cases, you’ll be working with active speakers, which have built-in power amps and do not need a separate piece of equipment to work. In fact, connecting them to a separate power amp might even damage them. 

Therefore, you could go from your preamp straight to your speakers. As long as they’re active speakers, they’ll work just fine. 

Guitar and keyboard amplifiers also have built-in power amps in them, which is why they can function as single units that don’t make you carry different individual amps. Not only that, but they also have built-in preamps, which include the whole EQ, so you get an all-in-one setup by default. 

The same goes for most consumer electronics, such as home theater systems, stereos, CD players, and so on. There’s a power amp included in all those cases, which is why you don’t often see them and why you might wonder if they’re necessary at all. 

What Is a Preamp?

preamp
Preamp

A preamp is an amplifier that boosts weak input signals to get them to line level, which allows them to be further processed by the rest of the amplifier/recording chain. It also removes noise, which improves sound quality. It should not significantly change your sound in other ways. 

Usually, your preamp is going to be the first thing that signals from your instrument or microphone come across. Those signals are usually weak and have to be boosted to line level. Line level is the strength level of the signal that’s standard for transmitting analog sound between different devices. 

For example, microphones might need a gain of around 30 to 60 decibels to reach line level, which is a significant increase. Guitars might need 15 to 30 dB, and even electronic instruments might need up to 10 dB to reach this level. This makes preamps a very important piece of equipment without which most of your recording and playback ideas cannot work. 

It can come as a separate piece of equipment, but it can also be simply a chip in an audio device. Quite often, the latter might be the case, which is why you might miss a preamp even if you use it all the time. 

Other Uses of Preamps

Apart from boosting your input sound, a preamp will typically have some other functions. These vary from device to device, so you’ll have to check what your preamp can do exactly, but here’s a look at some of the most common features. 

  • Phantom power: Phantom power is a means of supplying power to active microphones. Power is supplied via the same cable that carries the audio signal. Hence the name, since there is no visible source of power. 
  • Inputs: A preamp is going to have at least one microphone input, but quite often, it is going to have multiple ones. Typically, these are going to be line inputs, for vocals and mixers, and instrument inputs. 
  • Gain control: This might be the most important function of your preamp, as it is its primary function. It is also a great indicator of quality. If it doesn’t control the gain well enough, then it is simply not a good preamp.
  • Low-cut filter: A low-cut filter, otherwise known as a high-pass filter, is a filter that allows high frequencies to pass through while reducing the lower frequencies. This helps you reduce some of the bass to equalize your sound. You can also use it creatively to shape your sound how you want it.
  • Reverse polarity: This function comes in handy when you’re recording an instrument with two microphones. It reverses the phase polarity, which means that your microphones will be in phase and won’t cancel each other out. 

Will a Preamp Improve My Sound?

A preamp can improve your sound by reducing and eliminating noise and allowing you to control your gain, cut low sounds, and bring your microphones in phase. All of these functions will help you get a better sound. 

But if you’re asking about your sound as a musician, you’re probably wondering about your tone. In that sense, a preamp should not change things very much—in other words, it should be rather transparent. 

Some musicians prefer the sound of vintage preamps, which do provide some warmth and color to your tone, but modern preamps aim to be as transparent as possible. If you’re really into vintage preamps, you may be able to find some from the 1950s and 1960s, but you can also get imitations if you’re looking for a budget option. 

Do I Need a Preamp?

You need a preamp for the best control over your sound, and it is definitely a must for recording music. Otherwise, your signals will be too weak to work with, and your power amp will not be able to use them.

Without a preamp, you will not be able to bring your sound to line level, which means that your sound will be too weak for your sound card, camera, equalizer, or whatever it is that you might be using. 

Furthermore, using a preamp is going to give you more control over your input sound. This is especially true for guitars and basses, with which you’ll want to tweak various aspects of their sound, but also for vocals, where you’ll want to get as clear and transparent a sound as possible. This is most easily achieved with a preamp. 

Some audiophiles report that when building a music system, it might not be absolutely necessary to include a preamp if you’re only going to use it for listening to music. However, chances are that there will be a preamp somewhere in one of your devices, so you won’t even have to worry about getting a separate preamp.

Conclusion

A preamp is there to boost the weak signals from your microphone or guitar so that they can be processed by the rest of your audio devices. A power amp is there to power your speakers and further increase the volume of the input. Most consumer devices have both amps built-in.