How to Buy an Amplifier

Like if this guide is helpful
How to Buy an Amplifier

Irrespective of whether one wants an amplifier for an entertainment system at home, for a guitar, or for the car, one is truly spoilt for choice, and the choices are varied no matter which is needed. The features of an amplifier should be established at the onset, simply because amplifiers differ in terms of their intended use. After all, an amplifier to be used with a home entertainment system differs from one that is meant to be used in a vehicle, which in turn, is different from those to be used with an electric guitar.

Furthermore, one needs to establish what is required in terms of output. For instance, if one is looking for a guitar amplifier to be used at home, a small amplifier of less than 50 watts should suffice, and if it is needed for loud live performances, one can look at getting a 200-watt amplifier. When it comes to buying an amplifier, a buyer can turn to online retailers, like eBay, and also electronics retail shops. Aspects that need to be accounted for, in either case, include the type of amplifier one is after, the output, and the price.

What Does an Amplifier Do?

An amplifier receives small signals and amplifies them, while making no other changes. This task is not easy to accomplish when it comes to dealing with music because music is made of varied frequencies. In order to ensure that there is no change in the waveform, all frequencies need to be amplified uniformly, thereby resulting in no loss of quality. When an amplifier does not confine to this linear form of amplification, it can result in distortions of different kinds.

Deeply rooted in the realm electronics, modern day audio amplifiers work rather well when it comes to amplifying sound, although one needs to ensure that the amplifier in question comes with enough power to drive the speakers in question. On the other hand, amplifiers are looked upon as relatively trouble-free gadgets.

The Nitty-Gritty

Audio amplifiers mainly vary in four aspects, and these include dynamics, timing, transparency, and stereo imaging. Dynamics refer to variations an amplifier can portray in between individual note levels, and amplifiers that come with strong dynamics tend to offer better energy and longer life. Timing refers to an amplifier’s ability to present each note’s attack and decay, and well-timed amplifiers offer high coherence levels. Transparency is among the most crucial differentiator when it comes to choosing an amplifier because it helps when defining the unit’s subtlety. Stereo imaging helps distinguish how well an amplifier can portray voices or instruments in a three-dimensional setting.


Amplifiers can be segregated into different classes, the most common of which are Class A, B, and D. These mainly vary in efficiency, where a Class A amplifier results in a 30-watt output for every 100 watts of power they draw; a Class B amplifier generates 40 to 45 watts of power for every 100 watts of power it draws; and a Class D amplifier results in around 90 watts of power for every 100 watts of power it draws. The following table illustrates more differences when it comes to different classes of amplifiers.



Class A

Expensive, can get very hot, no crossover distortion

Class B

Little crossover distortion, more efficient than Class A

Class D

Small size, high-efficiency levels, no heating, problem in handling low impedance loads

In addition to these, buyers can also choose from Class AB, G, and H amplifiers. Class AB amplifiers may result in a little crossover distortion, and while they run in Class A until a given power output, they then shift to Class B in order to provide better efficacy. Class G and H amplifiers work to degrade signals and add complexity, which is done owing to the requirement of switching based on input signals.

The Relation Between Amplifiers and Speakers

When matching an amplifier to one’s existing speaker system, one should look at choosing an amplifier that delivers twice the power of the speaker system’s continual IEC power rating. For example, if a speaker system’s power rating stands at 350 watts and it comes with eight ohms impedance, one should look for an amplifier that is capable of producing 700 watts through an eight ohms load. In the case of stereo speakers, this should be 700 watts through an eight ohms load per channel.

Good-quality speakers are capable of handling transient peaks that exceed their power ratings as long as amplifiers work in distortion-free delivery, and amplifiers that provide additional headroom ensure that the power delivered to a speaker system remains undistorted. Maintaining peak transient capabilities is important in settings like studios, and in such instances, one should look at getting an amplifier that delivers six decibels more power than the unit’s continual IEC power rating. Low-powered amplifiers can lead to clipping, and one should know that low power can lead to system or speaker damage.

Types of Amplifiers

Audio amplifiers can broadly be categorised as monoblock, stereo, and multichannel amplifiers. Monoblock amplifiers work by driving a single speaker, so if one is looking for stereophonic sound, a pair of monoblock amplifiers is required. Stereo amplifiers, among the most commonly used, come with two channels and work by driving two speakers. These work well when it comes to playing music that is recorded using two channels, which is found in LPs, cassettes, and CDs. A surround or multichannel amplifier can drive five to seven channels, and are commonly used with modern 5.1 and 7.1 channel home entertainment systems.

Amplifiers for Home Entertainment

Given the variety on offer, buying an amplifier to pair with one’s home entertainment system can be confusing. Factors to be addressed in such a scenario include: establishing if the amplifier can function as it should even when the impedance load is low, the number of input and output points with which it comes, whether it comes with a DTS decoder, and whether it comes with a Digital Dolby decoder.

A majority of the home theatre systems sold now come with integrated amplifiers, and if such is not the case, one does need to look at acquiring an external amplifier. In addition, while most receivers in today’s world come packed with features, they are often found wanting when it comes to the muscle that is offered by power amplifiers. If one’s home theatre space is around 30 sq m, there is a good possibility that the receiver's amplifier does not do it justice, and in such instances, investing in a power amplifier makes sense. Establishing an amplifier’s power is determined on a case-by-case basis, and one should consider the size of the room, the capability of existing speakers, as well as the desired output.

Guitar Amplifiers

Beginners can make do with mini amplifiers, as these work well when used at home. Street performers have the option to look for amplifiers that do not require a power supply, since these amps rely on batteries instead. When it comes to recording, contrary to popular notion, one would be best off using a small valve amplifier.

Tube or Solid State?

Although a significant percentage of professional guitar players tend to use tube amplifiers, conventional thinking says solid-state amplifiers are capable of producing clean and superior power at a price which is definitely more affordable, and the absence of many vacuum tube manufacturers is regarded as the main reason behind tube-based amplifiers being more expensive. Newer alternatives offer users a blend of these technologies. One can buy a hybrid amplifier that relies on a tube-based preamp and a solid-state power amplifier.

While tube amplifiers offer users a rich and vintage tone, they tend to require more maintenance because the tubes can wear out quickly, and even though the sound delivered by solid-state amplifiers is looked upon as “cold” by many, they find more buyers owing to factors like reliability, affordability, and relatively clean tones.

Car Amplifiers

Car amplifiers are available in different types as well, and these include mono, two-channel, and multi-channel alternatives. Mono car amplifiers are designed to reproduce low-frequency sounds and come with inbuilt loss-pass and bass-boost filters. Class D mono amplifiers work well in such cases, given that they draw less current, produce less heat, and offer better efficacy in comparison to conventional alternatives. Two-channel car amplifiers should ideally come with high-pass filters, which are normally used with component speaker systems as well as full-range systems. Multi-channel amplifiers are used in vehicles that carry speakers on the front, sides, and rear, and can be coupled with subwoofers and full-range speakers as well.

Buying Amplifiers on eBay

eBay is home to almost all types of amplifiers, which include amplifiers for home entertainment systems, cars, and guitars. What one can expect to find on eBay are offerings by the best names in the business, and in addition to new amplifiers, consumers have the option to look for used amplifiers as well. Buying used amplifiers can result in considerable savings, and since not much can go wrong with amplifiers, barring their external appearance, this may be a good idea.

The diversity of amplifiers on offer through eBay includes 2.1 channel amplifiers, 5.1 channel amplifiers, 7.1 channel amplifiers, and more. Since eBay is home to scores of amplifier sellers, conducting a thorough search is always suggested. Not only does this help in establishing just what is on offer, it can also result in one’s coming by some great deals. What should go without saying, though, is that one should not count price as the only deciding factor, since quality does count when it comes to buying an amplifier.


When buying an amplifier, one should pay just as much attention as when buying a stereo or guitar, simply because it is just as important of a component. The first thing one should establish is the purpose that the amplifier is to serve, because different amplifiers are built for different purposes. Once the need is established, one should carry out extensive research in terms of specific alternatives on offer.

One should also understand that amplifier designs have evolved over a period of time, and newer technology does offer better alternatives than what were available, say, a couple of decades ago. The realm of electronics has seen a sea of change in the recent past, and although amplifiers that were made around 20 years ago still manage to stand the test of time, newer variants have managed to deliver much better results. Consequently, it makes sense to find the right balance between factors like class and price, and the ear can help to decide which amplifier to choose.

Have something to share, create your own guide... Write a guide
Explore more guides