Amplifier Testing
Audio amplifiers are essential in audio systems, designed to increase weak audio signals to drive speakers and produce sound. While each type of amplifier boosts audio, the way they handle signals, manage heat, and affect audio quality varies significantly, leading to different classes of amplifiers with unique advantages and trade-offs.
The main amplifier types—Class A, B, AB, and D—offer differences in sound fidelity, efficiency, and practicality which may affect which design is best according to various audio applications.
Class A amplifier: Class A amplifiers operate with current flowing continuously through output transistors, resulting in smooth, linear signal amplification. Known for their excellent sound quality with very low distortion, Class A amplifiers are inefficient, generating significant heat and consuming more power. They’re favored in high-end audio systems where fidelity is paramount.
Class B amplifier: In Class B amplifiers, two transistors each handle one half of the audio waveform. This design greatly improves efficiency but can cause “crossover distortion” at the point where the two halves of the signal meet, which may compromise audio quality.
Class AB amplifier: By combining the principles of Class A and Class B, AB class amplifiers reduce crossover distortion and improve efficiency. They’re a balanced choice for both home and professional audio systems, offering good sound quality with moderate power consumption.
Class D amplifier: Known for their high efficiency, Class D amplifiers use pulse-width modulation (PWM) to switch transistors on and off rapidly. This design minimizes heat and makes Class D amplifiers ideal for portable and high-power applications, with modern versions producing excellent audio quality.
How do you setup an amplifier for audio measurement?
Measurement setup is critical for nearly all applications, and for amplifiers this is no different. Audio analyzers are highly effective tools for audio power amplifier measurements, as they can handle the wide voltage and frequency ranges commonly seen in audio amplifier testing.
What are the most common measurements for amplifier testing?
Amplifier testing is unique among audio measurements because of the high power levels involved, as well as the amplifier’s direct effect on audio signal quality across various loads and conditions. Measuring amplifiers requires precision and careful calibration, as tests need to address how amplifiers manage power, distortions, and noise under realistic conditions. Amplifier tests are usually conducted at an output power of 1 watt as a standard reference level and can be done using an Audio Precision analyzer along with the APx500 measurement software.
Measuring Switch-mode Power Amplifiers
Switch-mode audio power amplifiers are becoming increasingly popular due to their smaller size, lower weight, and improved efficiency. Their advantages are obvious in low power battery operated personal audio players and laptop computers. However they are also progressively displacing more traditional linear designs in mainstream applications such as home entertainment systems, automotive sound systems, and professional installations where high quality audio is important.
