Amplification is what we need to make things louder. It’s the same principle with the row of Marshall amplifiers above and the guitar. The guitar could barely be heard without the amplifier.
It is exactly the same in an audio system. Regardless of what you would like to listen to; CD, records or radio you need an amplifier to make it louder.
How do amplifiers differ?
The most important thing for an amplifier to do is to make the signal louder. If it does anything else to the signal it will either distort or destroy it. Quad were once asked to describe a perfect amplifier and they said “it would be length of wire with gain”.
Olden day amplifiers used to have all sorts of bells and whistles on them. These included tone controls, graphic equalisers and in some cases even filters. People grew to like these controls but in reality they did little other than detract from sound quality.
British companies started to realise that taking these features off amplifiers and simplifying them ended up with better sound. So they began to do just that.
Compare this 80’s vintage Naim to the Pioneer. This one has nothing that isn’t needed. Basically you turn it on, select what you want to listen to and turn up the volume! Even the balance and mute controls tend to have gone now.
The philosophy of making an amplifier as simple as possible and spending all the money on what remains is called “straight line” or “signal path optimised”. For this reason there are some exceptionally good, affordable amplifiers around.
The Rega Brio R amplifier above is a very good example of that. It is as simple as can be.
Amplifiers perform two functions. The first is to handle the delicate signals coming into the amplifier. These could be a record player or a CD player or any other source. We call this part of the amplifier a pre-amp. The second is to produce the power and current to drive the loudspeakers and we call this the power amp. An integrated amplifier is an integration of the two in one box.
When you are looking for the highest performance it can be beneficial to split the two parts of an amplifier into separate boxes. Since the pre-amp deals with minute high quality in-coming signals it can be better to isolate it from the “noisy” part of the amp that deals with high current. The advantages can be substantial. A dedicated pre-amp can be laid out neatly in it’s own chassis with a dedicated power supply that is unique and not shared with the Power amp.
Since less is more is often the case with amplifiers modern pre-amps are often little more than high quality volume controls and input selectors. What makes them so good however is the quality of the design AND the components used in the design. In electronics if you double the tolerance of a component you often triple the price. Resistors that cost pence can soon run to many pounds if you specify the very highest tolerance. Even volume controls can actually impact on sound quality. The very finest volume pots are audibly superior, have better channel balance and last much longer too.
A more recent development is the integration of pre-amps with DAC’s. Since many of our sources are digital these days; it can make a great deal of sense to merge these two technologies together.
The power amp drives and controls the loudspeaker. It needs to have enough power and current in order to do this. Many people mistakenly think that power is everything. In reality most of us only use less than twenty watts, even when we are alone in the house listening to AC/DC at full pelt. It is the quality of the first ten watts that matters rather than the quality of the rest.
It begs the question therefore about what a good amplifier needs if not power. The answer to this is speed and precision. It is the job of the power amplifier to control the loudspeaker and that is as much about stopping the cones as it is about starting them. The amplifier basically needs a reserve of current so that it can draw on it to match the demands of the music. It needs to be able to move drive units to the full extent of their pistonic ability and then stop them moving every bit as quickly.
Low distortion is probably the most important factor in good amplifier design. Amplifiers need to deliver enough power quickly and do so without distorting and to have enough left in reserve not to fall flat on their face when the music rises to a crescendo again. Think of it as a free revving engine.