Learn to Design Audio Amplifiers

Learn to Design Audio Amplifiers

Some people ask me, starting from where if want to learn to design the amplifier. A simple question but the answer is difficult. I'll try to answer it simply, which may help beginners who want to learn to design an amplifier.

What is an amplifier? Many people can assemble the amplifier, even claiming to design the amplifier but if asked if the amplifier might be confused. Amplifier comes from the word amplify which means to strengthen. So the amplifier is a tool to amplify the electrical signal. The electrical signal has voltage and current. So the amplifier is a tool to amplify the voltage and / or electric current without changing the waveform. In the audio world, amplifiers are used as a means to amplify audio signals (electrical signals with frequencies from 20 Hz to 20 kHz) and their output is connected to speakers whose job is to convert the audio signal into an acoustic (sound) signal.

Learn to Hear

Before we start learning to design audio amplifiers we must learn to rate a sound system . The initial purpose of  sound system  used at home is to present unplugged music performances (without sound system) into the house. Unplugged music performances are  recorded on tape media, LPs, MiniDisk, Audio CD, SACD, HDCD, DVD-Audio, etc. with certain techniques so that when played in the room it will give the impression that the music show is in the room. This is called high-fidelity (hi-fi).

Therefore we must often go to unplugged music shows to recognize the sound of musical  instruments  . So we can distinguish unplugged music performances with recorded music played in a room. How can we judge the sound of guitars, pianos, drums, and other musical instruments if we have not heard the sound of the instrument directly? Acoustic guitars sound like electric guitars will not be a problem for us, as long as the voice is melodious, if we have never heard the sound of a guitar.

Sound reference (reference) is important. Without reference we can not judge the sound system sound is TRUE or not. We only judge her voice MERDU or not. The melodious voice for everyone is different. But normal people can distinguish the sound of musical instruments. So the sound system judgments by COMPARING the output with a reference .

Learning to Measure

Audio engineer from the past until now trying to define a good amplifier specification is like what and how to measure it. Starting from its function that only strengthens without changing its shape, add or subtract, then the amplifier specifications include:

1 - Total Harmonic Distortion (THD).

2 - Intermodulation Distortion (IMD).

3 - Slew rate or full power bandwidth.

4 - Signal To Noise Ratio (S / NR).

5 - Input impedance.

6 - The output impedance can also be expressed as damping factor .

7 - Gain (magnitude of gain) or can be expressed as input sensitivity.

8 - Power Supply Rejection Ratio (PSRR).

By knowing the ways of measurement, the design of the amplifier will be faster and not just trial and error. The most important thing is to look for a relationship between the measurable and the audible.

Measurement technology will continue to grow along with the development of electronic component technology and understanding of amplifiers.

Learning Electronic Theory

This is often forgotten by many people. How to design a good amplifier without studying the theory of electronics? Do not know what voltage, current, impedance, power and laws govern the relationship between them. Do not know how electronic components work. It's like people want to be a doctor but do not want to go to medical school, so they become shamans. Fortunately the design of the amplifier is not directly related to humans as its object. So by trial and error it does not matter. But indeed many Indonesian people who trust the dukun than doctors. Likewise, there are still many trusts of electro-shamans rather than electro engineers.

Electronics is essentially from the science of Physics. The exact science or science that everything can be measured and proven. But because electronics is an applied science (engineering) then it takes creativity.

ANISTARDI