What is an amplifier? What are the differences between a preamplifier, power amp, and integrated amplifier, and how should you choose one?

What is an amplifier? What are the differences between a preamplifier, power amp, and integrated amplifier, and how should you choose one?

Many newcomers to home theater setups are confused about the purpose of an amplifier (and even less about what a media player is...). This is because many consumer TVs, projectors, and stereo systems already have built-in playback and amplification functions, leading to a lack of understanding. "Can't a TV just play music directly? Why buy a media player?" "Can't you just connect the speakers to the TV? Why do you need an amplifier?" After doing some research online, they find themselves even more confused... What are preamplifiers and power amps? What is an integrated amplifier? What are the differences? Is there a difference between home theater and Hi-Fi amplifiers?

A home theater amplifier, also known as an AV amplifier, AV receiver, AV amplifier, AV receiver, etc., is essentially the same thing. An AV amplifier (especially a preamplifier) is the core hub and processing center of the entire home theater system; all devices in the system need to be connected to the amplifier. However, despite its crucial importance, the power amplifier is often the most easily overlooked component. People tend to focus more on projectors and speakers. Today, let's discuss some frequently asked questions about power amplifiers.

What is a power amplifier?

A home theater surround sound power amplifier, more accurately called a receiver or amplifier, is a device that receives and processes audio and video signals to achieve better audio and video output for video equipment (TVs, projectors) and audio equipment (speakers).

A power amplifier is also short for a power amplifier. Another name for a power amplifier is "power stage," which is specifically designed to amplify "large signals" to drive speakers and produce sound.

Conversely, a "small signal" amplifier is called a "preamplifier," typically used in the audio industry to amplify weak signals directly read from players, turntables, and cassette players, before passing them to the "power stage" for further amplification. The requirements for a power amplifier are simple: fully amplify the input signal, ensuring the output signal is N times greater than the input signal, without introducing additional distortion. N times is the gain value. Specifically:

1. The amplifier gain should remain constant for different input signal values.

2. The gain is unaffected by frequency. Signals of all frequencies must be amplified by the exact same amount.

3. The amplifier gain must not add noise to the output signal or introduce additional distortion.

4. The amplifier gain should not be affected by temperature changes, thus possessing good temperature stability.

5. The amplifier gain must remain stable over a long period.

Are professional power amplifiers suitable for consumer use?

Horizontally, they can be divided into professional power amplifiers and consumer power amplifiers; vertically, they can be divided into Hi-Fi power amplifiers and A/V home theater power amplifiers. Professional power amplifiers, as the name suggests, are mainly used in large professional venues such as conference halls, performance halls, concert halls, and even cinemas. Ordinary consumers don't need to consider them. Just like cars, a sedan or SUV is suitable for commuting—it's stylish, comfortable, and comfortable—but a heavy truck or tractor is not.

Consumer power amplifiers are easier to understand; they are used at home, or in small restaurants and living rooms. Due to space limitations, the output power of these amplifiers is generally not very high. Consumer amplifiers are further divided into Hi-Fi amplifiers and A/V home theater amplifiers. Hi-Fi amplifiers are mainly used for high-end music, while A/V home theater amplifiers are used for home movie viewing. Of course, they can also be used for listening to music, but the effect is not as good as Hi-Fi.

What are preamplifiers, power amplifiers, and integrated amplifiers?

Both Hi-Fi and A/V amplifiers have preamplifiers, power amplifiers, and integrated amplifiers. For Hi-Fi, the preamplifier mainly receives audio signals, adjusts volume, and amplifies the basic signal, while the power amplifier simply amplifies the output, providing higher power; with sufficiently good speakers, it can produce good results. An integrated amplifier combines the preamplifier and power amplifier, handling both audio signal reception and processing, as well as high-power output amplification. Hi-Fi preamplifiers are divided into active and passive types. Active preamplifiers amplify the signal through a power supply, while passive preamplifiers only adjust the volume. However, passive preamplifiers are very rare these days because the internal impedance of the audio source and the power amplifier differs significantly. Connecting the source and power amplifier solely with a volume switch results in a loss of dynamics, detail, and frequency response due to this impedance difference. Active preamplifiers, besides adjusting volume, also act as a buffer, providing initial amplification and reducing the impedance difference between the source and power amplifier.

For A/V home theater amplifiers, the preamplifier's role is even more powerful. It receives audio and video signals and performs audio-video separation, decoding, and optimization processing, resulting in a cleaner signal output without interference between video and audio. The power amplifier's role is similar to that of a Hi-Fi amplifier, amplifying the audio output. Integrated amplifiers work similarly, combining the preamplifier and power amplifier to perform audio-video separation and decoding while also providing power output. For a power amplifier, its job is to deliver the signal from the preamplifier to the speakers, or enclosures. It's not about being as loud as possible, but rather about having sufficient power. "Sufficient power" here means the ability to maintain the soundstage while preserving detail.

Can't an A/V amplifier be used for listening to music?

Not necessarily. However, compared to a Hi-Fi amplifier, its design and circuitry are more complex, leading to more interference with sound purity. To put it nicely, this results in coloration; to put it bluntly, it destroys sound purity. In this case, the likelihood of an A/V amplifier achieving Hi-Fi quality is relatively low. In other words, if you want both home theater performance and Hi-Fi sound, you'd better use two different preamplifiers, but the power amplifier can be the same.

Are separate preamplifiers and power amplifiers better, or is an integrated amplifier better?

Generally speaking, separate preamplifier and power amplifiers are better. Firstly, separate preamplifiers and power amplifiers allow for more precise manufacturing and use of higher-quality components. Secondly, because they are processed separately, there is less signal interference between them, resulting in richer detail. Integrated amplifiers are indeed at a disadvantage in this respect; even top-of-the-line integrated amplifiers cannot compare to top-of-the-line separate preamplifier and power amplifiers.

How to choose an AV amplifier?

First, it's important to understand that almost all manufacturers currently focus on promoting integrated amplifiers because they consist of a single unit, are simple to set up and adjust, and are easy to learn, making them very user-friendly for beginners. Separate preamplifier and power amplifiers, on the other hand, are more popular with experienced users because they allow for custom configurations, more diverse adjustments, and greater customization options. Secondly, integrated amplifiers have a drawback: upgrades are limited, especially in A/V home theater systems. The emergence of various new formats means that many older amplifiers cannot be upgraded as needed. In such cases, upgrading the amplifier requires replacing the entire unit. However, separate power amplifiers and preamplifiers are different. Power amplifiers generally don't require much upgrading; if they're sufficient, you don't need to worry about them, only replacing the preamplifier. Of course, the cost of this replacement still needs to be calculated.

How to choose the right model based on your needs?

a. Based on your budget. Within 10,000 RMB, you can basically only consider Japanese and domestic brands, as well as a few European and American models like the NAD 758.

b. Based on the number of channels. From 5.1 to 7.1, to 9 or even 11 speakers in Dolby Atmos, each speaker requires one channel to drive, so there's always an amplifier suitable for you. Note that the number of channels doesn't necessarily mean you need an amplifier with the same number of channels; backward compatibility is key. More channels are fine, fewer channels won't work.

c. Based on speaker type. For the same 7-channel amplifier, the power output can differ by a factor of two. The larger the speakers, the higher the power required.

Generally, small bookshelf speakers can be driven by an entry-level amplifier; large floorstanding speakers require at least a mid-range amplifier. If you also have a very large center speaker and want a rich, cinematic sound, a high-end amplifier is recommended.

Electronic products are updated extremely quickly, and home theater amplifiers are among the fastest-growing products in the home theater industry.

Why? Because there's a group of scientists who are constantly tinkering with new things. Amplifier manufacturers, in order to incorporate these new technologies, have to release a new generation of products every year.

Therefore, mainstream Japanese home theater amplifiers are updated annually. So how should you choose? Please refer to the following three sentences: "Buy new, not old; it mainly depends on your needs; buy early, enjoy early." In short, if you are a beginner, an integrated amplifier is sufficient, as there are high, medium, and low-end models. For experienced users, I believe independent pre- and power amplifiers are more suitable (they will eventually upgrade to a power amplifier), because they can tailor their setup to their specific needs and achieve different audio-visual experiences. Finally, remember: "Buy early, enjoy early," and once you've bought it, make the most of it. No one can accurately predict what new technologies will emerge in the future. When you are enjoying a great movie, nothing else matters—features, specifications, models, brands… Make good use of the equipment you have. One home theater amplifier is enough for you to use for several years, watching hundreds or even thousands of great movies. Whether it's worth it or not, you'll have your own judgment.