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Whether your source equipment is a turntable, CD player or music streamer, it needs an audio amplifier. This is a device which converts the low voltage signals transmitted by your sources into an audio signal which has sufficient gain to power your speakers. It makes no difference how good the speakers are - without an amplifier, you won’t hear a thing. If you’re using powered speakers, the position is different. In most cases, an amplifier provides power to speakers which are simply plugged into the sound system and have no independent power supply. The same applies to the use of headphones, which by their very nature tend not to have a separate supply. Powered speakers feature their own internal amps which are connected to and matched with the internal speaker or driver. Nevertheless, if you wish to expand your set-up by adding extra speakers, it’s a good idea to connect a separate amp in order to power them.
The prototype amplifier was developed in the early years of the 20th century by Lee de Forest and was an electron vacuum tube named the ‘Audion’. Other engineers made subsequent refinements, chiefly the introduction of the triode, made up of three components: a platinum plate as the positive terminal, a cathode as the negative terminal and a platinum grid as the mediator. Today we’d call the grid the input and the cathode the output. It wasn’t until after the Second World War that amplifiers were made safe for general use, thanks to the invention of the transistor, but modern amplifiers still operate on the same principles developed 100 years ago.
An audio amplifier has two functions, the preamplifier and the power amplifier stages. The preamp enables you to select multiple inputs and choose the level of gain you require. The power amplifier then adds that gain to the audio signal in order to power the speakers. It’s possible to buy separate amps to perform each of these functions, but given the current sophistication of amp technology, this is a matter of choice rather than necessity. However, it’s important to be aware of the cost implications involved in choosing a separate preamp and power amp as well as practical considerations including the amount of space you’ll need. Buying them as separate units is going to cost you more than if you get one that performs both functions.
Devices that combines both capabilities are known as integrated amps. Today, integrated amps are in much higher demand than separates and it’s hard to see any good reasons not to pick an integrated unit. For the price of two, you could buy one integrated amp that’s probably got much higher specifications than you’re likely to need.
Confusingly, in the UK, where some of the best audio equipment in the world is made, the term amplifier is widely used to describe integrated models as well as separates whereas in the US the distinction is preserved. If you’re buying from a British company such as Rega Research or Bowers & Wilkins, it’s worth bearing this in mind.
Now that we’ve unravelled some of the mystery about amplifier terminology, we’ll look at the definition and functions of a receiver. In many ways, their purpose is very similar. A receiver is essentially an amplifier with a built-in radio feature. If you’re using one, then you simply select the radio in the same way that you would any of the other audio sources and play it through the same pair of speakers. In this sense, any receiver is an amplifier, but amplifiers without the radio option are not receivers.
The invention of the receiver was made possible by the same technology behind the first amplifier. An engineer named Edwin Armstrong worked on the possibilities of the vacuum tube and created the regenerative receiver. In collaboration with the American Marconi Corporation, Armstrong made the breakthrough which took radio communication from its two-way manifestation and turned it into a medium for mass broadcasting. The first notable use of the new technology was the broadcast of the 1921 boxing match between Dempsey and Carpentier.
The receiver became very popular during the 1960s. They were developed to save space by combining functions in one unit. In those days, there were only two choices if you wanted to listen to music: vinyl records and radio stations. This made receivers particularly useful in the US where the proliferation of radio channels meant you could find new music easily. Mainstream and specialist stations thrived. Many other countries had extremely limited sources of broadcast music. In the UK, the first popular music station was the BBC’s Radio 1, launched in 1967, and commercial stations didn’t appear until the 1970s. In contrast, music radio in the US had been flourishing since the 1920s.
For decades, receivers dominated the market, particularly in the US. Innovations such as stereo receivers further consolidated this dominance and for many years, the proportion of receivers far outweighed the number of amplifiers. The development of digital formats changed the audio environment by introducing the first competition that the two giants of music delivery, vinyl and radio, had ever faced. However, the attractions of music radio weren’t diminished by digital and receivers remain an essential part of every music lover’s sound system.
One of the most significant trends in home entertainment we’ve seen in recent years is the development of the home theater system. Once upon a time, the only source of audio visual was the television, which came with built-in speakers. These had minimal tone control allowing you to adjust the volume and change the balance between bass and treble. That was the extent of customisation for many years. Programmes made for television were adequately served by this equipment, but any films broadcast on TV channels were shown with none of the sophisticated sound you’d get from watching them in a cinema. Innovations like surround sound were impossible to replicate. As for music programming on TV, even the most popular shows like Soul Train, American Bandstand and The Johnny Cash Show had no way of breaking free from the audio constraints of the television.
The advent of home video players merely emphasized what was lacking. Suddenly you could watch films at home without having to pick from the selections offered by the networks. But they sounded flat, with tiny treble and a general feeling of compression. If you’re old enough to remember the first time you watched ‘Jaws’ or ‘Taxi Driver’ in the cinema, you’ll understand this woeful discrepancy. DVDs and the short-lived Laser Disc format were initially hampered by the same underwhelming technology.
Manufacturers began to address the problem by designing televisions with audio outputs you could use to connect separate speakers and eventually soundbars. From this developed the concept of home entertainment systems as a genuine alternative to conventional television equipment, promising not just the visual but also the audio quality like the surround sound that was previously only available in the cinema. The idea caught on very quickly and not only did it offer a much-improved experience, but it created a new and lucrative market for the makers of audio equipment.
If you have a home theater system with a tuner function, then this is called an AV receiver, the AV standing for audio-visual. Instead of just the two channels of conventional stereo amplifiers, an AV receiver can output audio to a dozen or more channels, as well as presenting high quality video through an HDMI connection.
An AV receiver appears fairly similar to a standard audio amplifier but apart from the greater number of outputs, the big differences are invisible. It offers considerably more power and a whole range of new features. To make home entertainment systems even more attractive, AV receivers commonly provide options such as Bluetooth connectivity, room correction and wireless functionality. While you might expect to pay a premium for the technological extras, this isn’t necessarily the case and you can pick up a perfectly good entry level AV receiver for about $350.
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