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Class A vs AB vs D: Which Amplifier Is Actually Better?

Pro Audio Exposed

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Class A vs AB vs : understanding the engineering differences behind these three distinct amplifier designs.

Audio signal amplification is the fundamental task of any stereo system, yet the methods used to achieve it vary drastically. We strip away the marketing jargon to show exactly how different circuits handle the signal path, from the constant current draw of vintage designs to the efficiency of modern switching power supplies.

Using both vintage units and modern gear paired with oscilloscopes, we compare how Class A vs AB vs D behave under load. This analysis is for listeners who want to understand if the technical specs of their audiophile amplifiers actually translate to better sound in their living rooms, or if the engineering differences are mostly theoretical.

Subscribe for weekly audio gear breakdowns, and let us know in the comments if you prefer the efficiency of Class D or the traditional sound of Class A.

#hifi #audiophile #amplifier #classd #classa #classab #homeaudio #audioengineering #speakers #hifiaudio #ampclasses #purifi

20 Comments

@ProAudioExposed Creator 12 days ago Pinned

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@gsmollin2 8 hours ago (edited)

I use class AB in my sound systems. I use class D in my OEM Harman Kardon automobile system. It is long gone, but decades ago I made a 7199 tube headphone amplifier with a direct cathode-follower output. The 7199 is a great tube, and I mourn its passing. Some NOS is still available, or there is a decent substitute, I think, 6U8A. Whatever tube lineup you prefer, getting started in vacuum tubes with a headphone amplifier is a good way to go.

@rogerthomas9017 6 days ago

There is a subset of Class D amps designed to combine the effortless efficiency of a D output with the smoothness and warmth of tubes. The unit uses a single preamp tube in the initial stage feeding a Class D power module for final output. Claim is that the tube, when properly integrated with the D output, gives efficient and plentiful power with the overall sound character of a tube amp. Worth your investigation. Note: I own one, a Rogue Audio DragoN pair of monoblocs.

@mikehalimchanabdullah2204 7 days ago

I stick with the class AB amplifier. Hegel H600 is too strong on bass sound, Accuphase E5000 like a large stage , now the Accuphase E3000 just perfect fit for my daily listening.

@nelsono4315 6 days ago

excellent video! I have a Jeff Rowland class D power amp and I love it.

@johnstonewall917 11 days ago

I recently bought a small Class-D amplifier to replace a Sony amplifier that I bought over 20 years ago. There was nothing wrong with the Sony, but over the years my audio sources reduced to just 2, a turntable and a computer, the Sony could handle 6. My turntable has its own pre-amp, I actually only bought it to playback some 78s I had inherited. My new amplifier is less than 5% of the size of the Sony and I just needed a switch box to handle the 2 line inputs, no pre-amp required. The computer serves as a radio, CD player and playback of audio from a NAS. I used to have a rack full with lots of hi-fi components, they all became redundant over the years. I cannot comment on the sound quality, my hearing is now quite poor. The only large item I have is a powered sub-woofer under my desk. I am quite happy with this arrangement. I do miss, however, the Class-A amplifier I built 50 years ago designed by a friend. Sadly, it was designed for a 15 Ohm loudspeaker.

@sumitgenzyme 6 days ago

Class AB is my pick..as always

@MrRoberacer 2 hours ago

It is absolutely true. It took decades but the most recent iterations of class D or it's variants (class I for example) are literally that accurate and clean but with the added advantage of being able to output insane amounts of power no longer measured in 10's or 100's of watts. I have 2 Hafler P series amplifiers which to this day are well respected for their exceptional sonics but true to their design they are limited on the output side. Technology marches on. "D" won the race simply because it could do what it does far more efficiently.

@justanotheryoutubechannel3102 8 days ago

It depends on tastes and system matching. I love class D clarity, but it sounded clinical on my Mission aluminum dome speakers, but really perked my NHT Superzero soft domes up. A softer sounding amp like an NAD would work better with more clinical speakers, but my zeros sounded muffled on NAD.

@HowToHomeLife 4 days ago

The latest generation of class-D amplifiers have certainly come a long way in audio fidelity plus the elimination and filtering of the high-frequency PWM carrier, the original class-D amplifier was: "Infinity Systems made audio history by releasing the world's first commercial, high-power Class-D switching amplifier in 1976. Designed by John Ulrick, this pioneering amplifier—affectionately known as the SWAMP (Switching Amplifier)—established the foundation for modern Class-D technology, setting new precedents in size and efficiency.". Compared to class-A audio power amplifiers (25-30% efficiency), and class-AB (50-70% efficiency), current class-D amplifiers offer better than 90% efficiencies greatly reducing heat especially for the surrounding "electrolytic capacitors" that will always fail first in all electronic circuits, but by far the "loudspeaker room interface" is the ultimate problem in audio! David Riddle

@LFOVCF 2 days ago

it's all down to how good your ears are.

@phillipsampson4001 5 days ago

Never used class A, Class D has never let me down, though i use class A/B in my Hifi

@eolhcytoos 4 days ago

Only people who are likely to be able to differentiate between an amp's sound are professional members of an orchestra or maybe an experienced sound engineer. The rest are likely to be very subjective. Nevertheless an interesting video.

@silviosarunic6709 5 days ago

Great video❤
But Class A is best as always…

@JasonGo-d7q 4 days ago

Class D has the most cleaner sound, it's way cleaner than the original source😅 the sound has been altered, so can i say it's a kind of distortion😂😂😂

@pumu7752 4 days ago

Better amplifier old valve based hybrid amplifier only because natural sound delivery it cost very high one million dollars,

@MaryKissaKangleon-tz4on 1 day ago

Class AB amplifier

@kman915 2 days ago

So, this is bias from my own experience. And I'll say i haven't had a lot of audio products or brands in my hands. But I'm gonna compare a JL Audio RD 4004 amp to a Rockford Fosgate T400.4 for mids and highs. The Rockford is class AB and The JL RD is a Class D. The JL sounded very flat and lifeless compared to my Rockford. The Rockford had more depth and character. It more musical. Even the old Rockford Punch 400-4 Amps sounded better than the JL RD. It was literally night and day difference. I have heard other cheaper brands that were class D and sounded okay, but. I'm with class AB all the way when it comes to mids and highs. For low bass, Class D is fine.

@its_lori9602 3 days ago

The class of the amplifier is not based on the circuit topology. It's based on the conduction angle. Class A: output stage conducts 360 degrees or the full cycle. Class AB > 180 degrees. Class B = 180 degrees. Class C < 180 degrees.