A preamp boosts a weaker signal, bringing it to line level, and a power amp boosts the line level signal before it reaches the speakers.
In other words, a preamplifier increases the signal strength to an acceptable level to transmit to the equipment in your chain. and by boosting the line level signal, a power amplifier increases the amplitude/loudness of the sound you hear through your speakers.
if you ever wanted to ask, what is the difference between a preamp and a power amp? but you don’t want to be that guy in the conversation who isn’t technically savvy; now you don’t have to. Let’s compare the two a bit more.
Many people, even those with a hobbyist interest in recording equipment, assume that a preamp and a power amp are two versions of the same thing. even though they are both a form of amplifier, they are very different indeed.
what is a preamplifier?
A preamp is one of the first things in your recording chain. takes weak signals from microphones or instruments with low impedance and adds a specific amount of gain. typically, the average preamp can deliver up to 60 db of gain.
A preamplifier is needed to provide your interface, mixer, amplifier, or other equipment with a signal that it can process.
If you haven’t already, you should check out our article on preamps and what they do.
what is a power amplifier?
A power amp is one of the last things, often the last before speakers, in your chain. the power amp takes the line level signal provided by the preamp and adds more gain, as desired.
As a beginner, a power amp is a bit easier to understand because it’s easier to make a connection to volume/loudness.
what makes them different?
When you consider the fact that they are both amplifiers, and both are placed to boost a signal, it’s easy to wonder what makes them so different.
A big part of what makes them different, if we want to think about it simply, is their place in the record/playback chain. if you don’t know what we mean by chain, it just means the path the signal takes through your equipment.
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for example, a sound source (instrument/mic), a preamp, an audio interface, studio monitors, would be a typical home recording chain. As you can see, the preamp is very close to the start and the power amp is very close to the end.
There may be variations, effects added to the chain, etc., but the preamp and power amp will never move out of their usual position.
The point is that while they both apply a gain boost to the signal, they do so for different reasons. primarily the preamp is there to create a line level signal, but you can also creatively add gain to alter the base sound that the power amp will have to work with. preamps can also cause distortion.
at the end of the chain, the gain added by the power amp has more to do with the final output because nothing else will shape the sound beyond that point.
It’s not just about the signal path and where the components are in the chain. preamps have other features and functions like phase inversion and low cut filters.
do I need both?
yes, you need both. when you look at them individually, you can see that each does what the other can’t.
a preamp doesn’t have the power to drive a speaker; you need a power amp for that.
a power amplifier expects a line level signal; you need a preamplifier for that.
technically you could go from a preamp directly to active speakers without a dedicated external power amp. but, only because active speakers have built-in power amplifiers for each driver. would not work with passive speakers.
For more information, see our article on the differences between active and passive speakers.
Now that we can see that a preamp and power amp have a crucial role to play, we can look at a few different scenarios.
home recording studio
If you’re setting up a small home recording studio, you need a preamp and power amp, but you may not have even realized it. the reason we say that is that audio interfaces have built in preamps and active studio monitors have built in power amps.
When beginners think of a recording chain in its simplest form, it’s a mic/instrument for interfacing with daw and studio monitors. so even if you’re not buying dedicated preamps or power amps, you still have both.
It’s common to buy an external head amp even if your interface has integrated head amps, but the same doesn’t apply to external power amps. add an external power amp before your powered speakers can do any serious damage.
All guitar, bass, and keyboard amps have a preamp and a power amp. In the case of an instrument amplifier, the preamplifier doesn’t just refer to the circuitry that boosts the weak signal to line level. refers to a complete section before the power amp that includes eq.
so the preamplifier here is not just a signal booster; it is responsible for shaping the core sound of the instrument amp. you can see that the position of the preamp and power amp are still at the beginning and end of the chain, respectively.
Home stereo systems can be all-in-one or assembled as a modular system through a collection of separate components. The great thing about going the separate product route is that you can mix and match components to create the system of your dreams.
Preamps and power amps are two of the most important units, and again, the chain remains the same: the preamp usually follows the sound source, and the power amp usually precedes the speakers.
In this scenario, you’ll have passive speakers, which means you’ll have to use an external power amplifier because there isn’t one built into the speaker.
it’s best to keep it simple; think of a preamp as preparing the signal for the rest of your gear and the power amp as preparing the signal for your speakers.
Even if you’re making creative choices with your preamp, it’s ultimately not final. the choices made at the preamp stage will be affected by whatever else you have in your chain, whether it be effects, your daw, or just how the power amp and speakers interpret the signal.
Just know that they have some fundamental similarities and some important differences, but both are vital to any setup.