Integrated amplifies, power amplifiers, pre amplifiers. The long and short of it.
I want an amplifier, but I see there are lots of different types - what gives?
There are a number of ways of achieving amplification, but lets start with what one actually is and what it's for.
What is one?
If you have a source component of any type (CD Player, Turntable, Tuner, Cassette Deck (really - you've still got one?!), iPod or other compressed music playback device, Audio Server, Reel to Reel (how cool are they even now?) or any other device), you'll most likely want to hear it through a pair of speakers. In order to do that, the signal that comes from your component will be at a line level and so will require amplifying to a level that can be passed to and power a set of speakers. The amplifier will take the line level signal and just as the name suggests - amplify it to the required level. At the same time it will give you control over that signal, allow you to turn up/down the volume, allow you to select different inputs, possibly allow you to change settings such as balance, tone and suchlike. During the process of this the amplifier will also possibly carry out a host of unseen functions to do with phase control, EQ where appropriate, gain control etc. However, we're not interested in the complexed inner working, merely the basics.
We can pretty much split this down into just two categories. 1). You can buy an Integrated amplifier - where in you plug the cables from your source components into the integrated amplifier, you also plug in the speakers to the speaker terminals, and you then switch between these various components you've plugged in and change the volume all from this same unit. or 2). You buy a pair of units. One Pre-amplifier, where you plug in your components and control the volume output and selection which then, via a set of output leads plugs into a separate power amplifier which generally has no buttons, but simply has speaker output terminals on the back.
Which is best?
That's one of those questions that it is almost impossible to answer. You can buy VERY expensive integrated amplifiers and also Incredibly expensive pre and power amplifiers. Generally, you cannot but very cheap pre power amplifiers to the same degree that you can integrated amplifiers. It could also be said that pre power amp combos may be seen as a step up from an integrated amplifier since the manufacturers have spent more time and money developing these components to do the specific jobs they have been intended for. However, there are plenty of very fine integrated amplifiers out there that will easily out perform pre power amplifiers, so this cannot be taken for granted. But it would be fair to say, at the very highest end of Home Audio, most manufacturers aim at pre power combos rather than Integrated. As always, look at what you need to do the job you're after it doing and see what is suitable.
So many versions!
Yes, there certainly is. Transistor amplifiers, Valve amplifiers, Class B, Class D, Pure Class A, Digital Amplifiers (not to be confused with class D), Linear, Single ended, Push pull, Triode, Pentode, Dual Mono, Mono-Bloc. What's the best one to have? There isn't one. Ignore all the claims, use your ears and you can't go wrong. People can be educated to listen out for things like depth, separation and background noise, but once this is done, the only one capable of making the right decision about that which you prefer can be you. No one else has your ears or you tonal listening taste.