When it comes to home theater audio equipment, preamps and amps are two of the most essential components. While they may seem similar (after all, they both have amp in the name), there are key differences between the two that can greatly impact both the quality of your audio setup as well as the actual components you may need to purchase to get everything working correctly.
Preamps boost an incoming signal just enough to manage it at all from a receiver, while an Amplifier boosts that same signal on it's way out of the receiver to the speakers. Preamps aren't typically external devices, instead they're typically built into receivers. Amps can be built in or external.
Below, we'll start by explaining these terms in the context of some other key home theater audio management terms before heading into how to figure out what you have already and what you might need. We'll make a pit stop by managing turntables and generally how to know when to add or manage these key components in you setup. Let's get started!
What's The Difference Between a Preamp and an Amplifier?
When it comes to audio equipment, the terms preamp and amplifier are often used interchangeably, but they aren't the same thing. Not even close.
A preamp is a device that takes a weak signal from a microphone, instrument, or other sound source and amplifies it to a line level. So, your TV's audio out that runs to the receiver, or a simple Aux-in cord–that is going to have a very low power signal, maybe not enough to even manage properly in the receiver. To boost it just a bit, the pre amp amplifies it just enough to work with before (pre) doing any other kind of management with the signal.
An amplifier, on the other hand, takes a line-level signal and boosts it to a level that can drive speakers or headphones. The amplifier, then, is downstream of the signal in the receiver. It will be the last step, or, indeed, you may use an external amp for this last bit of mileage of the signal to the speakers (more on that a bit later).
Other Key Home Theater Audio Terms You Should Know
Our experience with home theater audio is that it's a super cool effect that can be achieved only by wading into the mud that is understanding all these components. Here's a brief explanation the key terms, including amp and pre-amp, in context. This list is also in the order through which the audio signal will travel, which helps you understand a bit more what's actually happening in the loop here.
- DAC (Digital-to-Analog Converter): Converts digital audio signals to analog signals that can be used by audio equipment. Maybe you're using an aux-in cord so the signal is already digital. If you're coming from a turntable (more on that later), then the turntable itself likely has a DAC built in, or, more likely, you'll run actual wires from it to a DAC. Most of the time, the DAC is already figured out.
- Preamp: Boosts a weak signal to a line level that can be processed by an amplifier or other equipment. This is almost never an actual external device (see more on our turntable specific comments here later), instead it's typically built right into the receiver, even when the receiver doesn't have an Amp for the other “side” of the signal.
- Receiver: Combines a preamp, amplifier, and other features in a single unit. This is the thing with an actual volume knob that you route your home theater audio to, before it routes it somewhere else, like your stereo speaker system. It may or may not have an amp built in, and it can also sometimes use an external amp. We have a separate guide just for receiver's and sound quality you may be interested in.
- Amplifier: Boosts a line-level signal to a level that can drive speakers or headphones. This is where you can add more signal power to drive larger speakers or achieve more volume, noting that the amp has to be matched to the speakers for it all to work well.
To summarize: in a home theater audio system, the signal chain typically goes like this: Source (e.g. Blu-ray player) -> DAC -> Preamp/Receiver (one unit) -> Amplifier (which may be in the receiver or external, or not present) -> Speakers.
So, as you can see, when it comes to understanding a preamp vs. an amp, it isn't either/or, it's yes/and. And these terms can get confusing…be sure to skim our other articles on receivers vs amplifiers and preamps in a home theater specifically for a little more background here. And the rest of this conversation–what actually happens with these boosted signals–can be unpacked by going through our dedicated post on multi-channel home theater sound systems.
How To Know If You Need (Or Already Have) A Pre-Amp
When it comes to determining whether you need a preamp or not, there are a few things to consider. First, think about the sound quality you want to achieve. If you're looking for high-quality sound, a preamp can help you achieve that. It can improve the strength of your input signal, which can lead to a clearer and more defined sound.
Pro-Tip: Most receivers, and especially expensive home-theater receivers, have a pre-amp built in. So, you probably don't need to add one, but you should confirm it's there using the product page or specifications of your receiver.
Another factor to consider is the type of equipment you're using. If you're using a guitar amp or other type of amplifier, you still probably already have a preamp built-in. In this case, you may not need an external preamp. However, if you're using a mixer or other audio equipment, a preamp may be necessary to achieve the desired sound quality. Most home theater aficionados don't ever end up in this situation.
If you want to add bigger speakers, or want to pump out more volume, the way to address that is with the actual Amplifier on the other side of the audio signal equation.
Special Note: When To Use Phono Pre-Amps With A Turntable
When it comes to record turntables, it's important to understand that the signal coming out of the device is likely much lower than the signal coming from other audio sources. This means that in order to hear music from vinyl through your speakers or stereo system, you first need to boost the signal. This is where a phono preamplifier comes in.
Again, this isn't going to be an issue for most home theater geeks out there, but if you want a record player baked into your setup, note that it probably doesn't include a DAC or a pre-amp out of the box. If it does, it will have AV ports you can run to your Receiver and it's preamp as an input, but if your turntable doesn't have any digital output method, then you need a phono preamp like this one (on Amazon).
A phono preamp, also known as a phono stage, is an audio component that amplifies the signal from your turntable to a level that allows you to connect it to your sound system the same way you would with any other audio source.
How To Know When You Need An Amp Too
So when do you need an Amp, then? The answer depends on a few factors, including the type of audio equipment you have and the level of sound quality you're looking for.
One key factor to consider is the type of speakers you're using. If you have passive speakers, you'll need an amp to power them. A preamp alone won't be enough to drive the speakers and produce sound. On the other hand, if you have active speakers (which are plugged into a power outlet and have their own power), they already have built-in amplifiers, so you won't need a separate amp.
Another factor to consider is the level of sound quality and volume you're looking for. While a preamp can improve the quality of your audio signal, adding an amp can take it to the next level, boosting it to a point that beefier speakers can use it and allowing for overall higher volume.
Special Note: Pre-Outs and Using an External Amp with Your Receiver
A pre-out is a type of output found on many audio and video receivers. It allows you to bypass the built-in amplifier in your receiver and send the signal directly to an external amplifier or powered speakers. This can be useful if you have a high-quality external amplifier that you want to use instead of the built-in amplifier in your receiver, or if you want to use powered speakers that don't require an external amplifier.
We have a full guide on this, but the quick summary is that the pre-out ports are typically located on the back of the receiver and are labeled as such. They may be dedicated to specific channels or speakers, such as front left and right, center, or surround. Keep in mind that not all receivers have pre-out ports, so be sure to check your receiver's specifications before attempting to use an external amplifier or powered speakers.
Preamp vs. Amp, The Last Word
Understanding the differences between preamps and amplifiers is necessary for achieving high-quality sound in your home theater audio setup…and avoiding unnecessary expense and confusion! While they may seem similar, they serve different purposes in the signal chain and can greatly impact the overall sound quality of your system.
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