Higher-End Class A/B vs. Class A Integrateds

@erik_squires

Class A amplifiers have no crossover distortion at the 0 point because they use a “single” device to handle a complete waveform. This structure is incredibly power consuming, heat creating, and low on efficiency (usually around 25%) and power (25-30W is an average ouput).

Class B amplifiers use two, or more, devices in a complementary pairing with the “top” one handling the positive half of the waveform and the “bottom” one handling the negative half. The two outputs are then summed to give you the complete waveform with the point that the waveform goes from positive to negative (and back) being called the crossover point. Because of the lack of perfect linearity between devices there will always be some distortion at the point of crossover. Class B amplifiers are usually used for high power work.

A class A/B amplifier uses a class A stage for low power work and then “switches” to the class B stage for higher power work.  

See https://en.wikipedia.org/wiki/Power_amplifier_classes for help, too.

@erik_squires 

What's give you the idea that I wasn't refuting your comments regarding Class A crossover distortion?   I even supplied a reference to the Wikipedia page. I don't see any reference information backing your comments.  And how did you come up with Pass Laboratories distortion specs?  I checked their spec sheet and it lists no distortion specs whatsoever, and neither does their user manual (I checked the XA30.8's). 

So, I sat down with Bing's ChatGPT-4 system and asked it.  This is what it provided, including references, for the question "What's the differences in distortion between a class A audio amplifier and a class AB audio amplifier?";

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A class A audio amplifier is a type of amplifier that operates with all of its output devices conducting through the full cycle of the input waveform¹. A class AB audio amplifier is a type of amplifier that operates with its output devices conducting for slightly more than half of the input waveform².

Some of the main differences between a class A and a class AB audio amplifier are:

• Efficiency: Class A amplifiers are less efficient than class AB amplifiers, as they waste more power as heat and require more quiescent current¹². Class AB amplifiers are more efficient than class A amplifiers, as they reduce the power consumption and heat dissipation of the output devices².
• Distortion: Class A amplifiers have lower distortion than class AB amplifiers, as they avoid the crossover distortion that occurs when the output devices switch on and off¹³. Class AB amplifiers have higher distortion than class A amplifiers, as they introduce some crossover distortion at the zero-crossing point of the input waveform²³.
• Sound quality: Class A amplifiers are considered to have better sound quality than class AB amplifiers, as they produce more even harmonics and less hum¹⁴. Class AB amplifiers are considered to have worse sound quality than class A amplifiers, as they produce more odd harmonics and more noise²⁴.
• Power output: Class A amplifiers have lower power output than class AB amplifiers, as they are limited by the maximum current that can flow through the output devices¹⁴. Class AB amplifiers have higher power output than class A amplifiers, as they can deliver more current to the load by using pairs of output devices in push-pull configuration²⁴.

Source: Conversation with Bing, 11/13/2023

(1) Class A vs AB - Audio Science Review (ASR) Forum. https://www.audiosciencereview.com/forum/index.php?threads/class-a-vs-ab-do-they-really-sound-different.18415/.

(2) What are the Different Types of Audio Amplifier Classes?. https://www.audioholics.com/audio-amplifier/amplifier-classes.

(3) Class AB vs Class D vs Class A Amplifiers (The Truth). https://boomspeaker.com/class-d-amplifier-vs-class-ab/.

(4) The Difference Between Class A and Class AB Tube Amps. https://www.middle8reviews.com/difference-between-class-a-class-ab-tube-amps/.

(5) Class A vs. Class AB guitar amps - Sweetwater. https://www.sweetwater.com/insync/class-vs-class-ab-guitar-amps/.

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And your references?

Please don't impart incorrect information to our members in the future.

@soix 

My response was not AI generated. For reference I used my own knowledge, and refreshed it using items such as Tremaine's Audio Cyclopedia, Wikipedia, and ChatGPT because their all decent research tools.  Other than referencing them (properly) to provide further backup, everything was written by me. 

As for me, I’m an old analog electronics engineer since the 70’s who’s designed 6-track sound-on-film equipment, record cutting equipment, amps, crossovers, speakers and theatrical and roadshow sound systems.

I own a Pioneer M-22 class-A (which I can cook eggs on) and am presently rebuilding an HK Citation 11 pre.  In addition to these around my house I use a Revox A-77, a rebuilt Accuphase E-202, a dBX 1231 1/3-octave EQ, a Cambridge Audio DACMagic 200M, an Anthem Statement, an Arcam CD37, a Nakamichi cassette deck, and a JVC-QLY55F turntable with AT and Shure carts, a Sony STR-V35, a Denon AVR, and an assortment of Sonos devices.  I use REW for system setup.

Hope this answers your question.