Amplifiers are usually categorized according to their electronic configuration and method of operation. These categories are called “classes”. Each class comes with its advantages and disadvantages.
Class A Amplifiers: Class A amplifiers are a type of solid-state amplifier that operate in Class A mode, meaning that they amplify the entire audio signal without switching off the power supply. They are known for their warm, detailed sound.
Pros:
• Warm, detailed sound: Class A amplifiers are renowned for their ability to deliver warm, detailed sound, with good imaging and depth.
• Low distortion: Class A amplifiers have low distortion levels, making them a popular choice for critical listening applications.
Cons:
• Inefficiency: Class A amplifiers are inefficient, producing more heat and using more power than other types of amplifiers.
• Cost: Class A amplifiers can be more expensive than other types of amplifiers, as they require more components and engineering to achieve their desired performance.
There are two main types of Class A amplifiers: single-ended Class A and push-pull Class A.
Single-ended Class A Amplifiers:
Pros:
• Low distortion levels.
• Simple design.
• Warm and natural tone.
Cons:
• Low efficiency, leading to increased heat dissipation and power consumption.
• Limited power output.
Push-pull Class A Amplifiers:
Pros:
• Increased power output compared to single-ended Class A amplifiers.
• Improved efficiency compared to single-ended Class A amplifiers.
• Reduced distortion compared to single-ended Class A amplifiers.
Cons:
• More complex design compared to single-ended Class A amplifiers.
• Higher quiescent current, leading to increased power consumption.
The choice between single-ended Class A and push-pull Class A amplifiers depends on the specific requirements of the application and individual preferences. Single-ended Class A amplifiers are often preferred for their low distortion and natural tone, while push-pull Class A amplifiers offer increased power output and improved efficiency.
Class AB Amplifiers: Class AB amplifiers are a type of solid-state amplifier that operate in a hybrid mode between Class A and Class B. They are known for their moderate efficiency, affordability, and good sound quality.
Pros:
• Good sound quality: Class AB amplifiers offer a balance between the warm sound of Class A amplifiers and the efficiency of Class B amplifiers.
• Moderate efficiency: Class AB amplifiers offer moderate efficiency, producing less heat and using less power than Class A amplifiers, but more than Class D amplifiers.
• Affordability: Class AB amplifiers are typically more affordable than Class A amplifiers, making them a popular choice for budget-conscious consumers.
Cons:
• Distortion: Class AB amplifiers have higher distortion levels than Class A amplifiers, as they do not amplify the entire audio signal.
• Limited tonal options: Class AB amplifiers generally offer less tonal variation than Class A amplifiers, making it more difficult to fine-tune the sound to a specific taste.
There are two main types of Class AB amplifiers: linear Class AB and complementary Class AB.
Linear Class AB Amplifiers:
Pros:
Low distortion levels compared to Class B amplifiers.
Improved efficiency compared to Class A amplifiers.
Wide range of power output options.
Cons:
Higher distortion levels compared to Class A amplifiers.
Higher quiescent current, leading to increased power consumption.
Complementary Class AB Amplifiers:
Pros:
Low distortion levels due to the use of complementary transistors.
Improved efficiency compared to linear Class AB amplifiers.
Lower quiescent current, leading to reduced power consumption.
Cons:
More complex design compared to linear Class AB amplifiers.
Requires precise matching of complementary transistors for optimal performance.
Both linear Class AB and complementary Class AB amplifiers offer a good compromise between efficiency and distortion, making them suitable for a wide range of applications, from high-end audio systems to musical instruments and public address systems. The choice between the two types of Class AB amplifiers ultimately depends on the specific requirements of the application and individual preferences.
Class B Amplifiers: Class B amplifiers are a type of solid-state amplifier that amplify half of the audio signal, with the power supply being switched on and off to produce the desired audio signal. They are known for their moderate efficiency and affordability.
Pros:
• Affordability: Class B amplifiers are typically more affordable than Class A amplifiers, making them a popular choice for budget-conscious consumers.
• Moderate efficiency: Class B amplifiers offer moderate efficiency, producing less heat and using less power than Class A amplifiers, but more than Class D amplifiers.
Cons:
• Distortion: Class B amplifiers have higher distortion levels than Class A amplifiers, as they amplify only half of the audio signal.
• Limited sound quality: Some audiophiles feel that Class B amplifiers do not sound as warm and musical as other types of amplifiers, and that they can have a sterile or harsh sound.
Class C Amplifiers: Class C amplifiers are a type of solid-state amplifier that amplify only a small portion of the audio signal. They are known for their high efficiency, but are not commonly used in audio applications due to their poor sound quality.
Pros:
• Efficiency: Class C amplifiers are highly efficient, producing less heat and using less power than other types of amplifiers.
Cons:
• Poor sound quality: Class C amplifiers have poor sound quality, as they amplify only a small portion of the audio signal.
• Limited application: Class C amplifiers are not commonly used in audio applications, and are primarily used in RF (radio frequency) applications.
Class D Amplifiers: Class D amplifiers are a type of solid-state amplifier that operate in Class D mode, meaning that they switch the power supply on and off rapidly to produce the desired audio signal. They are known for their high efficiency and affordability. Class D amplifiers are commonly used in car audio systems, portable speakers, and other applications where efficiency and compact size are important.
Pros:
• Efficiency: Class D amplifiers are highly efficient, producing less heat and using less power than other types of amplifiers.
• Affordability: Class D amplifiers are typically more affordable than other types of amplifiers, making them a popular choice for budget-conscious consumers.
• Compact size: Class D amplifiers are often much smaller and lighter than other types of amplifiers, making them ideal for portable applications.
• Good sound quality: With advances in design and manufacturing, Class D amplifiers are now capable of producing high-quality sound, even though some audiophiles feel that Class D amplifiers do not sound as warm and musical as other types of amplifiers.
Cons:
• Complex design: Class D amplifiers have a more complex design than other types of amplifiers, making them more difficult to repair and maintain.
• Switching noise: Class D amplifiers can produce audible switching noise if not designed and manufactured properly.
Class E Amplifiers: Class E amplifiers are a type of high-frequency, high-efficiency solid-state amplifier that are used primarily in RF (radio frequency) applications.
Pros:
• High efficiency: Class E amplifiers are highly efficient, producing less heat and using less power than other types of amplifiers.
• High-frequency operation: Class E amplifiers are designed to operate at high frequencies, making them well-suited for RF applications.
Cons:
• Limited application: Class E amplifiers are not commonly used in audio applications, and are primarily used in RF (radio frequency) applications.
• Complex design: Class E amplifiers have a more complex design than other types of amplifiers, making them more difficult to repair and maintain.
• Limited frequency range: Class E amplifiers are designed for high-frequency operation and may not perform well at lower frequencies.
Class F Amplifiers: Class F amplifiers are a type of solid-state amplifier that use a combination of Class C and Class AB modes to amplify audio signals. They are known for their high efficiency and good sound quality.
Pros:
• Good sound quality: Class F amplifiers offer a balance between the efficiency of Class C amplifiers and the good sound quality of Class AB amplifiers.
• High efficiency: Class F amplifiers are highly efficient, producing less heat and using less power than other types of amplifiers.
Cons:
• Limited availability: Class F amplifiers are not as widely available as other types of amplifiers, and may be harder to find and purchase.
• Complex design: Class F amplifiers have a more complex design than other types of amplifiers, making them more difficult to repair and maintain.
Class G Amplifiers: Class G amplifiers are a type of high-efficiency solid-state amplifier that use multiple voltage rails to produce the desired audio signal. They operate in a hybrid mode between Class A and Class B, using a low voltage rail for low-level audio signals and a high voltage rail for high-level audio signals.
Pros:
• High efficiency: Class G amplifiers are highly efficient, producing less heat and using less power than Class A amplifiers.
• Good sound quality: Class G amplifiers offer a balance between the warm sound of Class A amplifiers and the efficiency of Class B amplifiers.
Cons:
• Complex design: Class G amplifiers have a more complex design than other types of amplifiers, making them more difficult to repair and maintain.
• Limited frequency range: Class G amplifiers are designed for a specific frequency range and may not perform well at frequencies outside of that range.
• Limited availability: Class G amplifiers are not as widely available as other types of amplifiers, and may be harder to find and purchase.
Class H Amplifiers: Class H amplifiers are a type of solid-state amplifier that use two or more power supplies to deliver the desired audio signal. They operate in a hybrid mode between Class A and Class B, using a high voltage power supply for high-level audio signals and a low voltage power supply for low-level audio signals.
Pros:
• High efficiency: Class H amplifiers offer high efficiency, producing less heat and using less power than Class A amplifiers.
• Good sound quality: Class H amplifiers offer a balance between the warm sound of Class A amplifiers and the efficiency of Class B amplifiers.
Cons:
• Complex design: Class H amplifiers have a more complex design than other types of amplifiers, making them more difficult to repair and maintain
. • Limited frequency range: Class H amplifiers are designed for a specific frequency range and may not perform well at frequencies outside of that range.
• Limited availability: Class H amplifiers are not as widely available as other types of amplifiers, and may be harder to find and purchase.
Class I Amplifiers: Class I amplifiers are a type of high-efficiency solid-state amplifier that use a high-frequency switching power supply to produce the desired audio signal. Class I amplifiers are similar to Class D amplifiers, but are designed for high-quality audio applications.
Pros:
• High efficiency: Class I amplifiers are highly efficient, producing less heat and using less power than other types of amplifiers.
• Good sound quality: With advances in design and manufacturing, Class I amplifiers are now capable of producing high-quality sound.
Cons:
• Limited frequency response: Class I amplifiers may have a limited frequency response compared to other types of amplifiers, and may not perform well at low frequencies.
• Complex design: Class I amplifiers have a more complex design than other types of amplifiers, making them more difficult to repair and maintain.
• Switching noise: Class I amplifiers can produce audible switching noise if not designed and manufactured properly.
Class S Amplifiers: Class S amplifiers are a type of high-efficiency solid-state amplifier that use a switching power supply to produce the desired audio signal. Class S amplifiers are similar to Class D amplifiers, but are designed for high-quality audio applications.
Pros:
• High efficiency: Class S amplifiers are highly efficient, producing less heat and using less power than other types of amplifiers.
• Good sound quality: With advances in design and manufacturing, Class S amplifiers are now capable of producing high-quality sound.
Cons:
• Limited frequency response: Class S amplifiers may have a limited frequency response compared to other types of amplifiers, and may not perform well at low frequencies. • Complex design: Class S amplifiers have a more complex design than other types of amplifiers, making them more difficult to repair and maintain.
• Switching noise: Class S amplifiers can produce audible switching noise if not designed and manufactured properly.
Class T Amplifiers: Class T amplifiers are a type of high-efficiency solid-state amplifier that use a Tripath technology to produce the desired audio signal. Class T amplifiers are similar to Class D amplifiers, but are designed for high-quality audio applications.
Pros:
• High efficiency: Class T amplifiers are highly efficient, producing less heat and using less power than other types of amplifiers.
• Good sound quality: With advances in design and manufacturing, Class T amplifiers are now capable of producing high-quality sound.
Cons:
• Limited frequency response: Class T amplifiers may have a limited frequency response compared to other types of amplifiers, and may not perform well at low frequencies.
• Complex design: Class T amplifiers have a more complex design than other types of amplifiers, making them more difficult to repair and maintain.
• Switching noise: Class T amplifiers can produce audible switching noise if not designed and manufactured properly. (Reference: Tripath Technology Inc. "Tripath Technology: Class-T Digital Amplifier Technology." Tripath Technology Inc., Web.)
