Amplifiers

An amplifier does a couple of things.
It allows you to select a source, volume control, balance, etc. and amplifies the signal of the source. This is the functionality of a pre-amp.

 

The output of a pre-amp is unsuitable to drive a speaker.
The power amp has a fixed gain (most of the time 26 dB) and it amplifies the incoming signal.
The output is suit to drive a speaker.

Put a pre-amp and a power amp in 1 box and you have an integrated amp.

Audioanalyse PA90 integrated amp

 

Some use a passive preamp.
A switch to select the source and a attenuator for volume control.
The plus is that you remove a whole box of electronics, improving the transparency.
The down side is that you miss an amplification stage making the signal a bit weak.
It can be too weak to drive the speakers properly.

 

A more modern setup is to use a DAC with volume control and a headphone out.
This combines DAC and pre-amp in one box.
Use active speakers (build in poweramps with active crossover)

 

The alphabet

Amplifiers are classified according to their design. In audio the classes A, B, AB, C and D are used.

The subject is very well covered here.

 

Class D is very efficient, more then 90% of the power is used for the music signal. In case of Class A 50% of the power is dissipated as heat..

 

A modern Class D amplifier can deliver 320 Watt at 4 ohm in an almost Mac Mini size package. If global warming (or a low electricity bill) are your concern, these are the ones to go for.

 

Class D amplifiers are often build using OEM modules.
ICEpower by Bang & Olufsen

Direct Digital Feedback Amplifier (DDFA) by Zetex

UcD by Hypex

In 2011 Hypex introduced the Ncore, an improved class D design.

They claim it surpasses almost any linear amplifier.

Ncore

 

 

 

Source: Nutshell High Fidelity

Bi-amping

A lot of speakers have two pairs of binding posts, one for the woofer and one for the mid/high.
This allows you to drive the woofer and tweeter with separate amplifiers.

 

A much better solution is to drive each speaker with its own matched amplifier and do the crossover on the signal before it enters the power amps.
This allows for better filters than possible with passive components in the power part.
A lot of studio monitors are build this way.
This is called an active crossover.

All amplifiers sounds the same

A statement advocated by many today in the more critical audio forums.

Can a $500 solid state amp produce the same sound as a $12.000 valve amp?

Bob Carver claimed he was able to do so.

Read The Carver Challenge by J. Gordon Holt.