If you are reading this, there’s a good chance that you are looking for a new stereo amplifier. Or perhaps you’re about to upgrade an existing one. Here at TMS, we’ve covered the subject of what separates a good amp from a bad one on numerous occasions, and we’ve also compared many of the very best amplifiers currently available. Like in here

We throw in a lot of information in trying to make audio tech gear more accessible and better understood, but still, the curveballs of tech jargon can often remain a bit blurry.

So if you’re after a stereo amp for your home system, let’s take a slightly different approach. We’ll assume that we are choosing an amp for our own living room, and namecheck every detail that would determine getting the correct and best choice. By best we don’t necessarily mean the fanciest or the most expensive. We’ll simply talk about the important aspects of choosing and matching an amp to a set of speakers. 

Sony Stereo Amp| <a href=‘https://www.flickr.com/photos/78129336100/24982572970/in/photolist-xhe3VG-RkPggg-QLsfQw-RiSTca-Q4msAh-RabXR4-Q4b1nW-Q4b24f-Q6Yoi4-Q4b3YY-RhbgRC-RkCNh6-RhbiYd-RkCKgr-Q4b9nU-Q4b7mQ-Q4b6Lb-RkCLCV-RkCPeM-RkCNP8-R5Aczw-E2CoFW-N7jYMH-LeidVD-dJDs7B-9q3wy8-8xioEn-5WvSyY-8xtj2n-9sAfR1-7rv89w-4yt2ik-5NLom5-dJK2n5-5wMNHZ-5WrA1p-67ZESH-oUW94x-rmePSR-CSShnC-E4CdyJ-GSrskk-rNxYgi-DNH3tc-CSTHe5-CmEYhV-rNpKZu-rNwUAz-qPPRoR-4RC3xK’ target=“_blank”> RDesign182 </a>

Amplifier Basics

First off, let’s start with the simple bits - the amp is the chunky hifi component (and OK, they can come nearly palm-sized nowadays) that has a volume dial, increasing or decreasing the audio signal level which is fed to your speakers. The latter would be connected to the amp using speaker wire (also known as speaker lead or speaker cable). 

There has been an increased demand for standalone amplifiers lately. This is due to the fact that many millennials consume music and media by simply relying on online streaming services. So to pump your laptop or a portable device through a nice big pair of quality speakers, all you need (apart from said speakers) is a nice stereo amp. 

You wouldn’t and you shouldn’t connect an amp to active speakers. These are also known as powered speakers, because each of them would already have an internal amp connected and matched to the driver (internal speaker). Similarly, if you are already using a powered A/V receiver, you wouldn’t need an external amp. Every rule has an exception, though, and for the instances where you might be looking to expand an existing system, you could actually hook an additional amp and speakers. We’ll explain how below.

Choosing An Amp

Back to step one. Choosing a new amp would probably start with just an idea - something like: right, this is gonna be for my living room, I‘d need it to get my speakers pumping for the party on Friday night, or the movie marathon, or whatever. 

The crucial bit in the previous sentence is the mention of speakers. We’d start choosing an amp by knowing what speakers we have or are going to have. Their driver size, the power handling and the number of speakers you’d be using are the hard facts which would determine the main specs of your power amp - namely, wattage and impedance (don’t freak out - we’ll go into these in a little more detail below). Once you know these necessary spec figures, you could then sort the contenders by price to match your wallet.

For the majority of people, the easiest way of getting a decent hi-fi system is still to purchase a system-in-a-box (as in: an amp with separate speakers, all in one package) since everything is pre-configured and pretty much ready to play. But: opting for a stand-alone stereo amp would make a lot of sense if you are just amplifying your phone or PC/Mac.

There’s another scenario, which is if you have a preamp. Preamps, as their name suggests, come before the amp acting as ‘hubs’ for all of your audio sources, allowing you to switch between them at will. Think of a DJ Mixer, which may have many different sources (turntables, a laptop) plugged into it.

They also ensure that the levels fed to the input section of the power amp are optimal and correct - neither too hot, nor too quiet. If using a preamp, the way to connect it would be by sending the left and right outputs of the device into the left and right inputs of your power amp and bingo, you’re set.

Preamps can come in many guises, such as dedicated hifi preamp, a (non-powered) A/V Receiver, or, as we said,  a DJ or line mixer.

Volume Knob | <a href=‘https://www.flickr.com/photos/martin_thomas/3323193088/in/photolist-64Eewy-3zWMap-4MG4Xr-9ZpTTA-4nLubF-d8auoJ-d71shu-d8aubq-DwcCZ-a51Dj2-5T2ggh-9bnRwp-9ZmZnc-cfUd-jJNGr9-D6Djdh-EfiyGw-2jEcPi-f7iLDo-uqUuB-DCtf-biKddF-QKPSz-biK8fH-7zFTGR-qENVMY-biK6aT-Dn7mKH-biK3p8-4r1BsN-bB4V41-gY5n8F-cwojCE-qh3QfG-ehPg6P-shTrjJ-ra6do4-akyVxr-cCzNuU-estZdh-qPRHce-d8atM7-d8au3N-4QpEAp-4r86na-4QtSqo-4AXeST-4MDpUo-5AyduZ-GYrQx’ target=“_blank”> Martin Thomas </a>

Amp Types - And Which One To Pick

Powered A/V Receivers (a receiver with an integrated amp) are the most popular type for home theater installations. These can be stereo or multichannel affairs (5.1, 7.1, etc.), and handle video as well as audio.

Standalone Stereo Amps are the ones needed to power a single audio source into a pair of speakers. These don’t have source selection, or for that matter, any bells and whistles apart from volume controls.

PA Amps are very similar in design to stereo hi-fi amps. They just have a volume control for each channel, but the difference is that they are spec’d to deliver huge power - from 250 watts all the way up to 3000 watts per channel. They are designed for pro music venue applications - anything from clubs, music venues and stadium shows. You probably don’t need to worry about these.

Tube Amplifiers are essentially like regular stereo hifi amps but using military-grade vacuum tubes in their internal output circuitry. Tubes are famed for their exquisite portrayal of dynamics (quiet and loud) and may be that’s why you’ll see tube amps mostly in high end audiophile setups. They are distinct from solid state amps, which use electronics. This is more of an amp sub-type - so you could have a standalone stereo amp that runs on tubes.

Then there are Mono and Multi-Channel Amps. Amps can also be distinguished by their number of channels - a mono amp would have one channel only, stereo - two channels and surround amps can vary enormously - from six channels (5.1) up to 15 (13.2) and possibly more.

Matching Amps To Speakers

Matching the wattage of an amplifier to a set of speakers is paramount. The amp should be able to deliver, without a struggle, what the speakers can handle at their optimal state of performance - in other words, when they are loud as hell. 

Audio signals are essentially like waves, and the high point, or the peak, is the crucial bit in terms of how audio signals affect amps and speakers. The loudest sections of a song should not present a problem - for neither the speakers, nor the amp. 

If they do (and let’s start with the speakers), it would be when the amp is pushing audio ‘peaks’ well above the handling capacity of a speaker, and…well, let’s just say you will hear it. It sounds like a tearing, flapping distortion noise. This can result in blown speakers, even after a short while. So yeah - don’t do it.

The second scenario of amp/speakers mismatch would be when the loudest audio peaks challenge the amp instead. This would be in the case of the amp being underpowered for the connected speakers, and the problem will manifest itself in signal clipping - the level light indicators (every amp has them) clipping into the red, basically saying: “That’s it, you’ve pushed me too hard, I can’t really handle that, can’t feed those speakers with the level you’re asking me to…oh God, I’m dying, send help.” 

This would lead to the amp heating up until it goes bang. Neither blown speakers nor blown amps are a nice thing to experience, and it’s not particularly safe either.

Good news - avoiding this is dead easy. Very simple rule to follow: your amp should be at least 50% more powerful than your speakers, measured in wattage. 

So: if your speakers put out 100 watts each (a number you can find using manufacturer websites, or manuals, or even the packaging itself), it’s easy to figure out. Your amp needs to have at least 150 watts of power. We say ‘at least’ - it’s always good to have extra amp power. If you have a 180 or 200 watt amp, so much the better.

Stereo Amp | The Master Switch

Impedance Matching

We mention and describe the term impedance quite possibly in every TMS piece - whether it’s about headphones or speakers. It describes drivability - how easily a piece of gear handles and responds to an electrical signal. Possibly the most confusing fact about impedance is that unlike wattage, the lower the impedance figure, the more optimal power you get out of the equipment. 

Impedance is a bit like how a garden hose delivers water to the far end. A constant flow of water would result in a different spraying power, depending whether you have a narrower or a wider hose. A much wider hose would give you less pressure, and a thinner one would be sending out a powerful, high-pressure spray.

Just like with wattage, you’d need to match your speakers’ impedance to that of the amp, andl uckily, most hifi-grade speakers and amps are designed to easily match. Let’s say you have speakers that put out 100 watts at 8 ohms. That means you need an amp that puts out 150 watts at…you guessed it, 8 ohms. Rule of thumb: equal impedances.

It’s (slightly) more complex than that, but only slightly. Let us just stress that if your speakers have a really low impedance, they shouldn’t be connected to an amp with a higher one. The other way is generally OK (low amp impedance, high speaker impedance) but in this case you’d be using only a fraction of the amp’s full potential. This is because impedance is directly linked to wattage - in the real world, an amp that pushes 400 watts at 2 ohms (Ω) would be able to push only half that - 200 watts at 4 ohms. It would be halved yet again - down to a 100 watts if connected to a 8 ohm speaker. 

Here’s an example. If you have a stereo amp pushing 200W at 4 ohms, you can actually connect it to a pair of speakers running at, say, 25W/8 ohms each. But you’d be utilising only a fraction of the amp’s power. To get the full 200 watts working, you could in fact add another pair of 8 ohm speakers as a ‘daisy chain’, e.g connected to the speaker outlets of the first pair of speakers. In this way, each side (or channel) of the amp would be feeding two speakers running at 8 ohms each and this would be equal to running a 4 ohm speaker on each amp’s side. 

This approach is often used in bars and commercial installations, where more spread and room coverage is needed. Choosing a low-impedance amp would allow stringing 2 and sometimes 3 speakers one after another on the same amp channel…but hey, this is something you probably don’t have to worry about.

Getting The Most Out Of Your Amp

First things first: setting your levels correctly. The maximum volume you should take it to should be roughly three quarters on the dial, or roughly 3 o’clock (assuming that your amp’s max dial level is roughly around 5 o’clock). The amp will be pushing plenty of clean, continuous power to the speakers and the remaining one quarter of power is left for handling the highest-volume peaks of the material. This is how pros set up amps and not only in home set ups, but for big event installations as well, using 6000 watt beasts. It really works.

You’ll know when a system has hit the sweet spot - you’ll have no clipping (red lights flickering) and everything will sound crystal clear at any listening level. This is quite easily achieved with bundled packages - the ‘home theater in a box’ type or similar. Things may get a bit convoluted when putting a system together, especially when you have separate components - a separate A/V receiver (preamp), a separate amp and so on. 

Believe it or not, some people still like to emulate the glorious Jamaican sound system-type setups in their living room. Starting with a source audio player (CD/Blu-ray), the signal would go into a preamp, followed by a graphic equalizer, which plugs onto a 3-way crossover unit (splitting the signal into three frequency bands - bass, mids and tops, each of which have their own amplifier), fed into three amps, pumping a (still stereo) mix for the listening pleasures of the whole neighborhood… 

Stereo Amp | The Master Switch

Cheat Sheet

Wattage: The power rating and capacity of amps and speakers. 

RMS Power. The wattage measure of continuous power that an amplifier can output, or a speaker can handle.

Peak Power: Normally referring to speakers, if their continuous (RMS power) handling is 100 watts, their Peak Power handling is typically four times that- 400 watts. 

dB: Decibels. A measure of loudness

Impedance: A value for signal resistance. With high impedance, when only a small current is allowed through and vice versa

Ohm(Ω): The unit of measuring impedance (electrical resistance)

Three Great Amps You Can Buy Right Now:

Rega Elex-R ($1100)

Rega Elex-RIt might not be a looker, but Rega’s amp is one of our favourites. It has absolutely flawless sound, as well as a flawless pedigree. It may be a little bit overkill for those just starting out, but if you’re looking for an upgrade to an existing system (and don’t mind a slightly dodgy remote) then this is the one you want.

Topping TP23 ($90)

Topping TP23Ideal for those just starting out. At less than hundred dollars, the TP23 offers a barebones but still very good experience, and is dead simple to set up and use. Just plug and play. It’s not going to trouble the big dogs, but for newcomers, it’s perfect.

PS Audio Sprout ($499) 

PS Audio SproutThe cute-as-a-button Sprout comes from a terrific audio marque. Doesn’t have a huge amount of power, but the small setups, it works really well. And the sound is just superb: rich and full, with absolutely terrific dynamics. Even sometime after release, this remains one of our favourites.

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