The Dos and Don'ts of Buying an Amplifier

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The Dos and Don'ts of Buying an Amplifier

Today's stereophiles have several audio needs that can be segmented into components that channel surround sound for film, potent stereo for music, clear low frequency power for bass instruments and restrained amplification tailored for cars. While most novice listeners choose the most muscular power amplifiers according to their wattage, this focus misconstrues the true role that amplifiers fulfil. When they are correctly matched with the maximum power capacity of all speakers in the system, amps can send out powerful, but restrained audio without overheating. Volume may seem to be the most desirable factor in a power amp, but resistance, measured in ohms, is a larger contributor to sound quality. The resultant damping factor ensures that the speaker cones respond only to authentic audio signals. When a sound system's resonance is refined enough to push out only the cone movements the musician intended, it is because the power amplifier has been chosen wisely.

Understand the Solid State and Tube Amp Debate

For as long as these two types of amplifiers have existed, the debate about whether solid state or tube amps are preferable has raged among musicians and audiophiles alike. The argument has changed with the advent of digital effects advances. The truth of the matter is that neither solid state nor tube amps are superior choices for every listener. They are best selected according to the function of the amplifier in question. Guitar players, cinemaphiles, and music listeners all have entirely unique sets of sonic demands.

Solid State


Transistors and software control the tonal quality of sound.

Tubes manage the tonal quality, distortion levels, and power of audio.

A high level of accuracy and clarity that lacks warmth. Distortion sounds inorganic and sharp. The crisp sonic value makes these amps a preference for fans of digital audio.

Organic tonal quality gives sound a warmth that is appreciated by traditional audiophiles. Positive distortion widens the sound stage for a layered audio experience.

Components are durable enough to allow for portability.

Each model has its own sound character, allowing musicians to handpick the tones of their amplifiers.

Intricate settings allow them to mimic the sounds achieved by other types of amps.

Durability is impaired, requiring frequent replacement after heavy use.

These have their own distinctive tone which does not adapt from model to model.

Sound is at its best at high volumes. Low volume listening generates a substandard audio experience.

Stereo listeners and musicians who hold a particular affection for organic audio find it worthwhile to dedicate the additional maintenance and expense that tube amps demand from their owners. Practically minded musicians prioritise longevity and portability, which makes solid state amps a preference within this niche. Nonetheless, many bass and acoustic guitarists choose tube amps for their variable tones and layered sound stage. Those who value budget-friendliness above all else select tube amps for their lighter price tags.

Don't Prioritise Power over Impedance

When power amplifiers are poorly suited to speakers, they lack control over frequencies, resulting in vibrations, ringing, and noise that doesn't belong in the intended audio. When an amp is too powerful for the speakers, it fuels, a tight bass tone might extend into a booming, decayed sound. The amplifier's damping factor needs to match speaker impedance so that every sound generated is expressed precisely. Wattage needs to be inversely proportionate to impedance, which is measured in ohms. Ideally, impedance and power output are compatible when the woofer has a similar RMS wattage to the amplifier.

Adapt ohms to speakers

Car amplifiers typically have an impedance value of four ohms, while systems with more than one woofer can reach a maximum of eight ohms.

Don't neglect the impacts of bridging.

Bridgeable amplifiers change the way wattage is expressed. When multiple amps are linked in parallel, wattage per ohm multiplies according to the number of amps used. Overloading more than two amplifiers to quadruple the power only leads to overheating and damage.

Calculate operating channels using RMS Power.

The amplifier's RMS wattage must increase in proportion to the number of channels being used. Connecting amps to parallel satellites is a complex task best handled by experts.

Don't ignore tested frequency bandwidth.

When the amp's bandwidth is uneven, frequency distortion can create noise. There are several types of noise, with frequency distortion being the most obvious to the human ear.

Pay attention to power at various impedance loads.

When amplifiers have reserve current capability, they are powerful enough to drive lower ohm values. This is expressed by power into ohm impedance where amps can use twice the power to push half the impedance.

Consider Power Efficiency

Amps that are power efficient are less likely to overheat, keeping audio noise-free. Class D amps have an efficiency of 80 per cent, while class A and B components have only 50 per cent efficiency.

Don't Choose Amplifiers Without Considering Room Size

Volume is a core consideration when building a sound system for large, high roofed rooms and outdoor zones. Home entertainment systems need to send clear audio to all seating areas in the room. In large or oddly shaped rooms, this can present a challenge but a simple change of speaker placement overcomes these problems. Adapting volume to room size demands an understanding of how loudness, power, voltage, and decibel changes relate to one another.

Decibel Change and Volume

Voltage amplification and Gain

Watt RMS

Aspects that alter power demands

Decibels measure sound pressure (SPL) or relative levels. It is the latter that is most applicable to power amps. The minimum audible decibel change is plus 1, while the addition of 10 decibels demands double the wattage.

Voltage amplification is equal to the voltage output divided by the voltage input. The ratio between output and input measures the level of power the amp sends to every frequency, thus measuring sound quality at different volumes. Ideally, the audio power response curve will indicate that mid-range, bass and treble frequencies receive positive decibel scores.

Amplifiers that have wattage that is too low for speakers can cause damage. Too much power can clip waveforms which leads to distortion. For outdoor events and large rooms, amps with a high RMS wattage must be matched with satellite speakers with high maximum wattage capacity.

Speakers generate an increase of 4 decibels when placed indoors. The distance between the audio source and listener weakens decibel values. This means that amplifiers need significantly more power when listening distance and room size increases.

The challenge of selecting power and volume in amplifiers lies in the intricacies involved in achieving power that does not result in noise. A perfectly selected amp can send sound signals to their destination without losing any information. Distortion is present in all power amps but audible noise is not. To achieve a complete absence of detectable distortion, clipping and feedback must be minimised. Decreasing preset levels can prevent output clipping, while feedback and distortion can be eliminated by choosing amps that have ample headroom.

Don't Underestimate the Preamp

Preamps add an additional measure of control to a home sound system and are also valued by professionals working in a studio environment.

Phono preamps

Used to amplify the weak sound signals generated by magnetic cartridges in turntables.

Professional Audio Preamps.

Used to push extra power between musical instruments or vocals and recording technology.

Multi-Channel Preamps.

For musicians who need multiple amplification for several instruments, these preamps ensure that each channel is directly adaptable.

Vintage Preamps.

These are usually tube preamps. High quality components come at a higher price in comparison to other vintage preamps but when compared to newer components, there are significant savings to be made, particularly for audiophiles who value the organic tone of tube-based amplification.


Booming volume is considered an asset to search for by those choosing amplifiers, yet these components have several other tasks to perform before sonic signals are allowed to reach the satellites of the system. A great amp produces low, middle and high frequencies with equal competence. Amplifiers have been performing these tasks exceptionally well since the Seventies, making certain high end brands from the disco era some of the most sought after components. As time progresses, manufacturers are gaining fresh perspectives of noise and what generates it. This has allowed contemporary models to overcome some of the hurdles standing in the way of sonic perfection. Ultimately, individuals have their own sound preferences, making the amplifier a component that is particularly prone to personal taste.

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