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How to choose the right amplifier

Getting your amplifier choice right is critical to creating up a good quality system. It will be flexible enough for you to listen to all of the musical sources you have and few you might add later; and it will form the central hub of your listening experience.

Choosing an amplifier can be a daunting task. But it doesn’t have to be. If you know what an amplifier does, the different types you can choose from, and have a few clear ideas on how to start looking (or listening), the job gets a lot easier.


That’s what this article is for: to help you find the amplifier that’s best for you.


We break the subject down into five main sections:


Right here, right now


You press ‘play’ on the remote and settle back. Andy Summers’ guitar rings out; syncopating with the sharp percussive whack of Stewart Copeland’s snare, and the rounded, guttural drive of Sting’s bass. The sound is alive before you – a powerful, dynamic experience that sounds for all the world like the band is right there in your lounge room. This is what top-quality music is all about!


Time to shift gears. You reach for the remote again, and change sources. At first the sound is barely perceptible – it comes from almost nowhere but gradually fills the room before your very ears. Percussion at the rear of the soundstage; strings to the left, swelling as the movement builds. Double-basses and cellos to the right. The woodwinds join in, stage-centre. In just a few, joyous moments your room is filled by a full symphony orchestra in full flight – one of the most impressive experiences in live music, here in your own home.


When your breath is taken away by what you’re hearing, when you can close your eyes and believe that a three-piece band like The Police or the 70 musicians of a full symphony orchestra are in your home performing just for you, then you’ve truly entered the world of hi-fi.


And right at the centre of these performances is an otherwise unremarkable metal box: your amplifier, working hard to produce the highs and lows, the full dynamic range and exhilaration of an artist’s performance. When an amp is not doing its job well, that’s when you notice it. Otherwise it is the unsung hero of the musical experience: powerful, accurate, transparent and above all, real.


What does an amplifier do?


At first glance the job of the amplifier seems very simple. It takes the low energy signal from your source devices (such as a CD player or a turntable) and beefs it up into a higher energy signal to drive your speakers.


But when you get down in it, there’s more going on than meets the eye. A good amplifier does its job with the absolute minimum changes to the characteristics of the signal that comes into it. What comes out of, say, your CD player goes into the amplifier and then goes out to the speakers with minimal changes, only louder.


An average or a poor amplifier changes the signal to a greater extent than a good one, and what goes out to the speakers less like what comes in. Sometimes the changes an amplifier makes to the signal are due to poor design, or could be due to a manufacturer using cheap parts, or could be about the ability of the amplifier to access enough electrical power to do its job properly.


When the amplifier makes changes to the signal that come in you get a whole lot of unwanted and unwelcome characteristics added to what you end up hearing. An amplifier makes some changes by design, and these can be set by the listener – using treble and bass controls, for example – but ideally an amplifier should make the absolute minimum of unwanted and un-asked-for changes.


All hifi system amplification features two types of amplifiers: a pre-amp and a power amp. Sometimes these are sold as separate components and you connect them together yourself, but most commonly and most conveniently they are combined inside one box and called an integrated amplifier.

Know your amp from your receiver (and your AV receiver) A “receiver” is an integrated amplifier with an AM/FM radio tuner built into it. Whether you end up buying an amplifier or a receiver is a little irrelevant; it’s just that one will allow you to listen to the radio. The discussion about the quality of the amplifier remains unchanged. It also remains unchanged if you’re thinking about buying an “AV receiver”, which will also handle video. In this article we’re only discussing amplifiers. We’ll cover AV receivers in separate articles because there is a whole host of other issues to consider besides the amplifier when video enters the picture – no pun intended.

Test drive it to death!


Whichever path you take, you can’t tell how well an amplifier is going to do the job you need it to do without actually listening to it. The manufacturer or the retailer will tell you all about its specifications – its frequency response, total harmonic distortion, power output and the like – but that’s like being told a car has four doors, a V8 engine and power steering. You don’t know how it’s going to perform and whether you like it until you drive it.


Hifi experts will often tell you that choosing the amplifier is possibly the single most important decision you can make when you’re putting together your hifi system. Others will tell you that the speakers are the most important component. If you’ve built your speakers at The Speaker Project, then we’re going to assume you’re committed to these speakers being central to your system, so it’s absolutely true that the next most important decision you need to make is your amp. (We will discuss the selection of other hifi system components in future articles.)


Any good hifi shop will be set up so you can do comparative listening tests between all sorts of hifi components, and in all sorts of combinations. In a perfect world, when you’re choosing an amplifier, you could take your own speakers with you and listen to a range of different options played through them. If that’s not possible, you need to find a pair in the shop that most closely match your own. It’s about eliminating as many unknown variables from your listening tests as you possibly can.


Once you’re set up and ready to listen, play some source material that you’re already well familiar with. Listen to the music at a comfortable level, and listen to it louder than comfortable, too. Amplifiers (and speakers, for that matter) often reveal their shortcomings and performance quirks when you work them hard.


Above all, take your time. Switch between your various options as often as you need to so that you can get straight in your own head what you prefer the sound of. Don’t be rushed into a decision, and if switching back and forth all starts to get too confusing, walk away and come back another day.


What you like and what you don’t like the sound of is a fundamentally personal choice and there are only a few genuinely black-and-white, right-or-wrong issues. One such issue is that the music you listen to should never, ever, sound distorted. Distortion you can actually hear is a sure sign something has gone horribly wrong, somewhere. If you hear any distortion don’t bother spending too much time figuring out how or where it’s coming from; move on and try another amplifier.

The amplifier class system

There are different types of amplifiers, designated by “class”, and this designation refers to how the amplifier is laid out internally, how it works and how much power it needs to draw (and therefore how much heat it generates) to do its job.

There is a mountain of literature about whether Class-A amplifiers are “better” or “worse” than Class-D amplifiers. Purists will tell you Class-A amplifiers reproduce music best; but they are also inefficient and tend to run very hot. Class-D amplifiers are significantly more efficient, but their musical reproduction isn’t quite as good.

We started out this article by saying the aim of choosing an amplifier is to find the one that most faithfully reproduces the signals it receives from your source devices. That remains true, but the real world is often a bit messier than the ideal one. There is inevitably going to be a compromise between ease and convenience of use, performance and price.

How you trade those variables off against each other is up to you. We’ll look more closely at the world of amplifier topography in future articles.

What are you going to listen to?


If the quality of sound were the only issue you need to think about when choosing an amplifier, the task would be a lot more straightforward than it often ends up being. But there are other issues you need to think about as well.


For example, how many different sources do you want to listen to? Do you listen only to CDs, and do you want to use an analogue input (e.g. the red and white RCA plugs), or does your CD player have an optical output option? Do you also have a turntable, and will you need a special input (labelled on the amplifier as “phono”)? Will you be streaming music to your new amp, so does it need Bluetooth functionality? Will you hook up a DAC – and what sort of input does that device need?


It goes without saying that the amplifier you choose should cater to all the sources you’ll be listening to, and it’s good to have a couple of unallocated inputs left over, just in case you add something to your set-up later.


How many watts do I need?


The final consideration you need to make is how many watts you want the amplifier to provide.


The rule of thumb is to look for an amplifier that can provide twice the recommended wattage of your speakers. This is especially important if you plan on pushing your speakers to their maximum recommended loudness.


The with under powered amplifiers you will run into problems of clipping and excessive distortion when playing loud music with high dynamic range.

However, not all amplifiers provide the same sonic performance per watt as others. If an amp does not get the first watt right then it's unlikely the amp will sound good at higher volumes.


So while you want to look for an amp that has twice the wattage of your speakers, there are other factors to consider like how it sounds connected to your speakers and how it sounds at a volume that you will most often listen too.


If you don't plan pushing your speakers to their maximum volume then you can consider getting a lower wattage amplifier. It's not uncommon for audiophiles to run 20 watt tube amplifiers on speakers rated at 200 watts. They don't plan on running the speakers at their max acoustic output and enjoy the sound that their small 20 watt provides.


Which is the best one for me?


The amplifier that’s best for you is the one that sounds best to your ear, has all the input options you need now (and a couple more in case you expand your system later) and that you can afford.


That last issue is just as personal a choice as your preference in sound. A rule-of-thumb in hifi used to hold that your speakers should account for about half the total cost of your hifi system. So here’s some really good news. If you built your speakers with The Speaker Project, you outlaid a fraction of the cost of similar quality speakers if you’d bought them from a hifi retailer (and you had a hell of a lot more fun, too). So you can allocate a greater slice of your budget to your amplifier!


To do your The Speaker Project speakers justice, you need to drive them with a really good quality amplifier. You won’t regret the decisions you take now to make the most of what you’ve got.


The Speaker Project recommends


Amps can be as cheap as $40 and exceed $50,000. Within this price range there're so many great amplifiers to suit different taste and budgets.


Over the years, Atlas the founder of The Speaker Project has heard his fair share of amps. Keep reading to see his recommendations.


SMSL AD18


For the price, I don't know if there's a better option than the SMSL AD18. It's an integrated amp and comes with practicable features such as Bluetooth connectivity, analogue and digital inputs and a claimed 80 watts of power - that I doubt is true and expect it to be closer to the 30 watt mark. Albeit, enough to drive most speakers to a reasonable loudness.

Based on my listening impressions, the SMSL AD18 amp provides a warm laid back sound that conveys the major aspects of music. It falls short in the areas of bass control, dynamics and clarity.


This amp would suit anyone who's looking for an amp that sounds reasonable and has Bluetooth connectivity built in. The amp comes with a remote control, so you can adjust the volume from the comfort of your couch.

I will say that if you're looking to invest in some high performance speakers such as our Trohet speakers, then I would advise you invest in a more refined amp - keep reading.


Cambridge Audio AXA25


For $500 AUD you can pick up a brand new Cambridge Audio AXA25. This integrated amp provides that true hifi sound, punchy bass, accurate production of notes and clarity. I was thoroughly impressed with the sound quality of this amp especially considering its affordability.

It also looks great too, the brushed front panel along with the utilitarian styling provide a modern aesthetic.


The only down side is that this amp delivers a mere 25 watts, which means that the amp will struggle to sound good at high volumes - if you don't plan on listening to music loud then this shouldn't be a major issue. Secondly, the amp only has analogue inputs and does not have Bluetooth connectivity. Nevertheless, the latter can be solved by using a Bluetooth receiver such as the BluDento.


Audiolab 6000A


The Audiolab 6000A is an integrated amp that provides 50 watts and is regarded as a very good sounding amp within its price category. According to Whathifi.com, the 6000a "has a gorgeous sense of clarity and ample detail, leaving you listening to your music library comfortably for hours on end" - I agree as I found this amp to be engaging to listen too.

The amp also comes with Bluetooth, so you're able stream music directly from Spotify or the alike. While the cheaper amps like the SMSL AD18 mentioned have Bluetooth, the circuitry in the 6000a is far superior offering a enhanced listening experience.


Finally, the 6000a comes with a multitude of inputs, both analogue and digital, so you're afforded to connect your turntable and your TV's audio output. With the latter I recommend using your TV's optical output for this.


Musical Fidelity M3si


The M3si integrated amplifier is a special amp, it sounds powerful with its deep bass, detailed mid range frequencies and refined treble - I recommend this amp to people who want to hear the sound of true high end audio.

The M3si provides 85 watts, and can deliver power to the most demanding speakers thanks to its high amperage output. If you want deep controlled bass you need an amplifier that can deliver amps, lots of it!


This amp retails for around $2500 AUD, and for most this may be expensive or above your budget. But, my moto is, audio is like wine, and life's to short to drink bad wine. On top that, this is an amp you will have for life.


The way I describe this amp is that it makes music sound special, it brings out the emotions and is guaranteed to make the hair stand on your back. It's powerful and it's moving. The amp produces a "soundstage" that is bigger than the room itself, and gives the illusion that the musicians are playing in front of you. I should also note that this amp delivers excellent dynamic range, meaning both the softest and loudest sounds are easily heard.


In essence, this amp sounds like it isn't trying hard, it's confident.


The downside? The amp doesn't come with in built Bluetooth connectivity, So for that you will need a Bluetooth receiver - I recommend the Bluesound Node 2i, I've tested this device with the M3si and can confirm it sounds great.


Musical Fidelity M6si500


The M6si500 has to be the best amplifier I've heard below $30k AUD. It's bold and offers sonic perfection. While I don't own this amp, I would if I was in the market for a new one.


This amp is an absolute power house offering 500 watts into 8 ohms, so safe to say this amp will drive any speaker with ease. I've listened to this amp paired with our Trohet speakers and the sound was exceptionally good.


The bass was incredibly deep while controlled, every bass line was rhythmic and conveyed with ease. The mids were silky smooth while exceptionally detailed, the kind of mids that make you sink into your chair and want to hear music all day long. The highs were clean without any grain of harshness, just sweet and enough to make Goldilocks happy.


But where this amp really separates itself from the rest is is ability to produce the complex harmonics of music. Every amp can play the fundamental frequency, meaning the loudest frequency. But the magic happens in the production of the harmonics of a note, it's what makes music sound rich and emotive.


The amp retails for $6,000 AUD and for this price you'd assume it also makes you coffee and the rest. It's not cheap, and that's because this is a master piece of electrical engineering. It's akin to the Ferraris of cars.


The amp doesn't come with Bluetooth, and that's not uncommon for high end amps -They've been designed to focus on the amplification, and that's it. For an amp of the calibre I would recommend and a Bluetooth receiver from the likes of brands such as Bluesound, Matrix, Auralic and NAD.


What amp does the founder have?


Wonder what amplifier the founder of The Speaker Project owns?


Atlas (founder) was after an amp that offered a neutral sound while being accurate. The purpose of this amp wasn't only just for enjoying music, but also testing his speakers. He bought the Jungson JA88D(09) almost a decade ago.


The JA88D has been regarded by some as the best kept secret in hifi. The amp is an exceptional performer that rivals amps costing more than $6k AUD.



He picked this amp new for $1000 AUD, which is an absolute bargain. But like all bargains, there can be some consequence/risk involved. This amp had to be purchased from a dubious online store that had a reputation of poor customer service. Atlas took the punt and ordered the amp.


So a word of cation, if you're planning on buying one of these amps do your research into the retailer and their reliability. Audio forums are great for this.


As to sound quality, the JA-88D is neutral, yet renders music with great clarity. Deep bass is produced, however not exceptionally deep, especially when compared to amps like the M6si500.


Where the amp really shines is in the midrange; it's smooth like chocolate and transparent. I can listen to this amp for hours on end without fatiguing my ears.


If I were to say where the JA88D falls short I'd say it's the high frequencies. They're there, but not as engaging as more expensive amps like the M6si500. So if you're looking for super sparkly highs then this amp might not be for you. I consider the JA88D to sound quite dark in the sense that everything is there and reproduced accurately, its just that nothing seems to jump out or try and grab your attention.


The JA88D is an integrated amplifier based on a true differential design, something that is rare to find. Differential designs offer the benefit of reducing noise, which is the nemesis of accurate sound reproduction. The amp does not have in built Bluetooth connectivity, so an external Bluetooth receiver is needed. Atlas uses the BluDento paired with the Matrix Mini i Pro for Bluetooth connectivity.


An in-depth review of the JA88D(09) has been published by Austraian HiFi - a great read.


Want to build your own amp?


I'm going to be frank, building amps from scratch is complex, especially when the goal is to achieve accurate sound reproduction. If you haven't built an amp before I would advise on getting a kit.


There's stacks of kit amps out there, but not all are equal. I auditioned the Hypex NCore400 mono blocks and was blown away with how good they sounded. Incredibly detailed, rich and exceptional bass control. These amps are being used by some of the big brands like NAD, and are selling for several thousand.


I will say that while these amps sound great, they do sound a tad clinical and aren't as captivating as amps like the M6si500. Albeit, considering the price that these amps can be built for they are a stellar choice.


If you want to read more about this amp then check out this indep r3wwed in depth by AudioScienceReview.com.


Written by Simon Hoyle


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