Tuesday, December 2, 2008

High level basics about Amplifiers

The purpose of an amplifier is to take an analogue or digital audio signal sent at line level and raise its amplitude then send it to the speakers to reproduce the live or recorded sound. 

An amplifier reproduces the sound exactly as it receives it (more or less) since it is not a perfect reproduction some distortion is added on top of the distortion that may or may not exist in the source signal. The level of increase is determined by controls on the device and is usually scaled from 0 – 100 incrementally. 

Some items of interest with regards to amps are:

  • Gain - the ratio of output to input power
  • Bandwidth – The range of frequencies the amplifier can successfully transmit
  • Efficiency – the measure of how much energy is converted to useful sound
  • Noise - Noise Factor is the ratio of Signal to Noise Ratio of input signal to that of the output signal
  • Slew rate - the maximum rate of change of output variable
  • Overhead – the amount in reserve over the min required by speakers 

The mistake many make is confusing loudness with sound quality – just because a system is loud does not mean the sound is good. Allow me to give you a simple rule of thumb is the bigger the speaker the more power needed to move it. 

Think about it this way

  • Pick up a pebble – how much effort does it take?
  • Now try to pick up a bolder – much harder right? 

Each speaker makes sound by moving its diaphragms to create sounds waves by moving are, the large the speaker the more are that must be displaced and the more power needed. That is why speakers typically come with ratings to let you know the min required to make then function at an acceptable sound level. And yet overdrive (drive speakers to hard) they try to move air faster than they are designed and this causes distortion in the quality of sound. 

Here is a bit of trivia – did you know a microphone is a form of amplifier?

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