What are the differences between Class A, AB, and Class D amplifiers?

What are the differences between Class A, AB, and Class D amplifiers?

Confused about the differences between Class A, Class AB, and Class D amplifiers? Join Paul as he explains the differences between these different amplifier classes. Have a question you want Paul to answer? No problem. Just head to http://www.psaudio.com/ask-paul/


  1. herr trigger on May 5, 2020 at 3:39 pm

    Do the current model PS Audio Stellar amplifiers use the new B&O amp module like the Bel Cantos or do they use the previous version? thanks-

  2. ملكة زماني on May 5, 2020 at 3:39 pm

    Why do we have two vOmin values in calss A amplifiers?

  3. M C on May 5, 2020 at 3:41 pm

    Hi. I have a question. I love
    vintage hifi from 80’s-90’s. I buy many old equipment and I noticed that they sound
    much less clearer (much less treble) than what they were sounding when they
    were new. What’s getting old in them? Is it the old capacitors  acting as filter? What’s the reason they sound
    much less clearer? THX

  4. Thomas Gonzales on May 5, 2020 at 3:42 pm

    Paul u da mane

  5. Tom Atkinson on May 5, 2020 at 3:42 pm

    I love it! I did not realise the heat is lower in class A during a max use (the speaker gets hot versus silence) that is a very good point! Then again maybe the impedance is higher for silence versus a sine wave? Either way, its the best explanation I’ve seen! Best Class D also. Class A/B for me now is the most mysterious. How does a A/B amp notice the zero crossing? I guess it fades to zero when the bias goes negative and there is a small cross-over when both sides run.

  6. Herr Bönk on May 5, 2020 at 3:49 pm

    I would describe a "class A" power amplifier as basically just a small signal amplifier stage scaled up, i.e. a transistor conducting half its maximum current when no signal is present. Then the "class B/AB" power amplifier instead being two mirrored transistor stages taking turns on the positive and negative sides of the signal. The downside of B/AB being risk of crossover distortion and the upside being almost no static current draw (just a minor bias current to overcome the non-linearity of transistors near zero current).

  7. Mitha Htoo on May 5, 2020 at 3:50 pm

    hi, some studio monitor using class d amp as said. when there is no audio signal , there is a hiss sound come out from the tweeter . is that normal? or need to fix?. not only the studio monitor , other electric guitar and instrument making a hiss sound too, thanks in advance.

  8. saikat bose on May 5, 2020 at 3:52 pm

    Yes this old person talks a lot and the same thing over and over again. But the fact remains that they hardly talk about some very small but important issues. Just a example have never seen anyone discussing the sound parameter adjustments in a av receiver which is in the audio set up. And lot of unnecessary talks

  9. itsabig on May 5, 2020 at 3:52 pm

    Okay Mr. Smarty pants…..what did we miss?….there’s A, and then B, then AB…..there IS a letter between B and D!

    Jesus, they let anyone on YouTube anymore………………meh

  10. Action Is the Magic Word on May 5, 2020 at 3:53 pm

    *Your voice is class A clarity*

  11. Gregory Trane on May 5, 2020 at 3:53 pm

    Class A amp’s are preferably more musical and defined. Class AB would share some of their characteristics. Tubes that are designed in this way preferably with class A would be the creme de la creme as in earlier Marantz products. Good review.

  12. Paul Morrey on May 5, 2020 at 3:54 pm

    Thanks Paul

  13. Salongo Edmond Mpungu on May 5, 2020 at 3:55 pm

    This is both good knowledge and skill. Thanks!
    You know, many have this kind of knowledge but can not pass it on to others using crayons like you have satisfactorily done.
    I’m following you from now on

  14. Fred on May 5, 2020 at 3:56 pm

    Thanks so much

  15. Real HIFI Help on May 5, 2020 at 3:57 pm

    Difference is that, class D are for people with small D#&5s, Class AB is better, but still small D#&5s, Class A is the sh#%.

  16. D Tec on May 5, 2020 at 3:57 pm

    thank you i learned something

  17. Simon A on May 5, 2020 at 3:57 pm

    Hello, little mistake about the class A amp.
    An idle amp don’t consume 100% of the nominal power, but only 50%.

  18. Marty Jewell on May 5, 2020 at 3:58 pm

    Nicely explained and very lucid. I didn’t really understand class D, do now. So now that you’ve closed one "can of worms", where does Hitachi’s class G and Soundcraftsmen’s class H fit in and are they a viable alternative??? Also what the heck is Carver’s Magnetic Field amp???

  19. Soultaker93 on May 5, 2020 at 3:59 pm

    Very informative video. Didnt expect class A amps to be thr least efficient, tho.

  20. Ryland C on May 5, 2020 at 3:59 pm

    Hi I have a pair of Arphi Super Challenger speakers. 50 watts RMS each Chanel. These are 42 year old speakers. Please suggest me an amplifier to match the wattage of the speakers. Thank you.

  21. OverLord_01TM reyes on May 5, 2020 at 4:00 pm

    learned a lot from that short video thank you!

  22. Decibel Audioworks on May 5, 2020 at 4:01 pm

    First time viewer and instantly subscribed because Paul is awesome 🙂

  23. BoudewijnvanHouten on May 5, 2020 at 4:02 pm

    To answer the question:
    Class A: is wasting power
    Class AB: is wasting less power as much as the designer allows to run quiescent current trough the amplifying devices
    Class D: No more power used as required to do the job.

    The Class of an amplifier doesn’t say much about the quality though.
    I’ve had harsh sounding heavily biased amplifiers (Krell) that didn’t sound sweet at all and sweet sounding Class AB amplifiers (Conrad Johnson, Jeff Rowland) that where moderately biased to only produce ten Watts in Class A.

    So the generalization here about the Classes of amplifiers and their sound is nonsense.
    All things equal: If you can afford it choose an amplifier with a healthy big powersupply, lots of output devices in parallel and chunky heatsinks.

  24. TB Player on May 5, 2020 at 4:02 pm

    The advertised RMS wattage of class D amps seem to be overrated.

  25. WHITEFORD PIPES HANDMADE By Michael David on May 5, 2020 at 4:03 pm

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  26. Pinoy keyboard warrior on May 5, 2020 at 4:04 pm

    Hey, where’s the class C amp?

  27. Moist Andy on May 5, 2020 at 4:04 pm

    hey, I ripped into some old commercial airline headphones and one of the speakers measured 30 ohms. How is the best configuration to amplify at different loudspeaker impedance?

  28. PJ Lawrence on May 5, 2020 at 4:05 pm

    Very good explanation. Thank You

  29. Golf1 D1 on May 5, 2020 at 4:08 pm

    Sir, my name is Daniel, I live in Sweden. I’m looking for help please. Can you please help me to recommend power amplifier for my speakers? I have 6 pieces of Meyer MSL-3 speakers and 2 pieces JSL Sound concert system bass speakers. Power: 1000 watts RMS. IMPEDANS : 8 OHMS * 2. Notes: if anyone can be a help, I was really appreciate thanks 😊.danielweah90@yahoo.co.uk

  30. Bhalchandra Lagu on May 5, 2020 at 4:10 pm

    Hi, good evening (Indian time).
    I have a question to ask. Whether stylus for 78 RPM records fits on regular magnetic cartridge or cartridge itself is different for 78 RPM records along with suitable stylus.

  31. Exxella on May 5, 2020 at 4:12 pm

    This is just a good pure hearted man of a person, thank you kindly sir for this Info.

  32. twoicyclops on May 5, 2020 at 4:13 pm

    Almost 100k subscribers

  33. real cartoon girl on May 5, 2020 at 4:13 pm


  34. jaygl0 on May 5, 2020 at 4:13 pm

    Thank you!! Very instructive

  35. Danilo D'Aponte on May 5, 2020 at 4:14 pm

    I really like the way you explain stuff. Are your products available in Europe?

  36. Rick C on May 5, 2020 at 4:17 pm

    Whichever company that figures out how to deal with the "complications" of making a great class D amplifier, and offer a 5.1 or 7.1 surround receiver using class D tech, at an affordable price and in a compact design will get my $$$ – just a matter of time! I love how good my Lepai TA2020 sounded (after fixing noise issues) for only $20-$30.

  37. CryBite on May 5, 2020 at 4:18 pm

    Amazing video.
    Definitelly keep that up if you are.

  38. herr trigger on May 5, 2020 at 4:18 pm

    Does a gain cell pre amp sound different (as in, less faithful to the source) than say, an Ayre K-1, Benchmark LA4 or Bryston BP-26 pre amp? I love PS Audio but I can’t do A-B comparisons between any PS Audio Gain Cell pre amps and the others and I don’t want to take a step back. Thanks Paul you are the best!

  39. Randall Maness on May 5, 2020 at 4:19 pm

    QSK QSL! =]


  40. Fat Italian on May 5, 2020 at 4:22 pm

    Class d sucks

  41. frajr86 on May 5, 2020 at 4:22 pm

    Wow you explain very well 😀 Thanks so much!!! I didn’t understand if I have 3 differents amplifier well built A-AB-D
    it doesn’t matter which one I choose because they all sounds good or class A is better anyway? Thaaaankssss

  42. khalid hadebuis on May 5, 2020 at 4:24 pm

    class d amplifiers are less heavy not ?

  43. Rory Gallagherfan on May 5, 2020 at 4:24 pm

    In the 70’s I had a class A power amp, "Ampzilla" by Great American Sound. It ran so hot, it had two cooling fans and kept my room warm, summer and winter. I didn’t like the sound. Not dynamic at all. Plus it was prone to sudden, catastrophic failures, and had to be sent to California to be repaired. Finally, GAS went bankrupt. I bought a class AB power amp, the NAD 2200. What a difference. Great amp, great sound. Still going strong today. After 32 years, only had to replace the output relays, which were of very poor quality.

  44. Bennett R. on May 5, 2020 at 4:25 pm

    But what about a Classe amplifier?

  45. Jose Peixoto on May 5, 2020 at 4:31 pm

    Man,i head my head tilted to the side, like your dog in the back, listening… lol

  46. Kandela Brown on May 5, 2020 at 4:31 pm

    What is a class C then?

  47. Leelahs Playhouse on May 5, 2020 at 4:32 pm

    Could anyone test out my application? Encounter: androidcircuitsolver/app.html

  48. Vital O on May 5, 2020 at 4:32 pm

    Hi, I was watching this video and would your help or advice on what amplifier to buy. I have really good speakers JBL ES 90 BK and using Denon AVR -S500BT Receiver.. I feel like I am not getting the full potential of my JBL since they can max at 400 Watts. While my Denon Receiver powers only 75 Watts per channel. I don’t have lots of money so I am looking for a good budget class AB amplifier. Not very expressive but good enough to boost my Denon . I can combine the external amp with Denon through pre- out

  49. kabelo matthews on May 5, 2020 at 4:32 pm

    Great explanation. Many thanks.

  50. Javier Garcia on May 5, 2020 at 4:35 pm

    Thanks a lot I Finally Understand it

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