Class A versus A/B

Discussion in 'Solid State' started by opusarlo, Jul 29, 2018.

  1. opusarlo

    opusarlo AK Subscriber Subscriber

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    OK, I have scoured the web tonight while working in the hopes of learning why people pay massive dollars for those huge class A amplifiers. The irony is, the more i read about them, the worse they are for everything. power hungry, inefficient, hot...so then, why would I want to spend the long dollar on a class A or class A - A/B? Why not just get the more efficient class A/B?

    Not a troll post..I am on the cusp of purchasing an amp and want to learn why the Adcom 5802 commands around 1000-1500 while a Yamaha MX-630 "Class A" can't even crack $1k.

    Please be gentle. I am still learning here. My goal is to have a system capable of handling a pair of Maggies...i hear I need between 300 and 500 WPC
     

     

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  2. opnly bafld

    opnly bafld AK Subscriber Subscriber

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    Look at class D amps like Crown XLS and many others.

    MX-630 is an A/B amp.
     
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  3. dr*audio

    dr*audio Fish fingers and custard! Subscriber

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    I have worked on many class A / AB amps and usually I can't hear the difference between the 2 modes. The one time I heard a difference I thought it sounded more harsh in class A, and the amp was working properly. A class AB amp, when properly biased, has negligible crossover distortion. You can't see it on a scope. I am not going to say it isn't there, but you can't see it, and I contend it is inaudible.
     
  4. c_dk

    c_dk Addicted Member

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    Most Magnepan speakers need quality high current amplification over quantity amplification.

    I think Levinson really was the first to step up with a class A amp back in the late 70s and their impact in the marketplace seemed to be the seminal movement into the huge marketing hype leading to many Class A marketing schemes.

    As the doc stated, a class AB amp properly functioning has so little notch distortion it is not audible.

    Almost all amps have some parts of their circuits run class A, but there are many other, much more important factors, to consider in finding the right amp to run any particular set of speakers not the least of which is getting the speakers to work with your room not have them work against each other.
     
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  5. ghamilton

    ghamilton Super Member

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    A good class A/B design is the way to go. Not all A/B amps are equal.
     
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  6. bberkom

    bberkom AK Subscriber Subscriber

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    I can’t really tell the difference between Class A and Class A/B modes on my Yamaha M-45. It does run significantly hotter in Class A mode since it is biased higher by a factor of ten, but I usually just run A/B.
     

     

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  7. SaSi

    SaSi Seriously Illogical Subscriber

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    The reason why Class A is so fancied by 'high-end' aficionados is the brute force approach to solving a problem of amplification. Something like huge and heavy loudspeakers as an attempt to counter resonances or 1000lb turntables made of steel.

    A medium power class A amplifier needs to be heavy (due to the large transformer and heatsinks) and big (to house these big things) and even heavier (to provide a sturdy frame and enclosure for all that heavy stuff. In theend you get your weight in equipment (or twice that if you are slender) and you have to pay an arm and a leg (or two) to get them.

    Another reason class A amplifiers may have such a following is that they produce mainly even order harmonic distortion while class B and AB produce odd order harmonics. And tube amplifiers produce (lots) of even order harmonics. And it has been observed that we - humans - tend to enjoy even order harmonics more. So class A solid state amplifiers may exhibit a "tube sound".
     
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  8. Silentnet

    Silentnet AK Subscriber Subscriber

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    What Magnepans? What size room? Seriously doubt you need that much power.
     
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  9. c_dk

    c_dk Addicted Member

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    I think the reality is that most amps promoted as "class A" are pseudo class A, they do not really meet the accepted engineering standards for that type operation.

    Except for the handful of models made by Levinson, Krell, Threshold and and I believe spectral most all ultimately switched into class AB at higher output levels.

    As in the Maggie question about compatibility with a Mac amp in the McIntosh forum, getting the right speaker location in the room will mean more to the best sound than the amp, especially the amp class.

    The OP is making quite the jump to the other side of the speaker spectrum......going from horn based speakers to sheets.
     
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  10. opusarlo

    opusarlo AK Subscriber Subscriber

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    Actually, that was a very clear comparison. So, class A will sound much better than AB. With that said, if my amplifier uses class A up to 50 watts I will enjoy the sound up to 50 watts more than the sound after that. If I need juice for 110 dB pipe organ sequences playing through a pair of maggies, I will be happier with something more along the lines of an Adcom 5802 or maybe even a big old Rotel. Did I get that correct? The difference is in the sound quality and not volume, right?
     
  11. opusarlo

    opusarlo AK Subscriber Subscriber

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    I have an iNuke already for the 2 subs, but I don't want class D for my mids and highs. want a versatile core setup that I can use for any number of circumstances including big maggies
     

     

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  12. opusarlo

    opusarlo AK Subscriber Subscriber

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    This was very reassuring to read. One less thing to worry about. This makes my buying choice so much easier. Thank you
     
  13. opusarlo

    opusarlo AK Subscriber Subscriber

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    music to my ears...thank you
     
  14. opusarlo

    opusarlo AK Subscriber Subscriber

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    This helps a lot - I only listen to pipe organ, and even then only angry pipe organ and I listen at very high volumes...Class A does not seem to fit into that equation very well. THank goodness...I could never stomach paying 12k for one monoblok...hell no.
     
  15. opusarlo

    opusarlo AK Subscriber Subscriber

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  16. Silentnet

    Silentnet AK Subscriber Subscriber

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    Class A does not necessarily sound better than A/B, there are a lot of different bias setups.
     

     

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  17. c_dk

    c_dk Addicted Member

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    Which is your local reference.....St Marks, laGrave, Fountain St. or Park?

    Most of the local organists in GR back in the day used various dual woofer Mac speakers and when we got their new offerings on display they all would show up to audition the new products. I did voice many of them with the Mac MQ equalizers to solve some of their room boundary issues.
     
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  18. Silentnet

    Silentnet AK Subscriber Subscriber

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    Also, again, what Magnepans? Better be huge, for organ. Mebrane slap may be a problem.
     
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  19. opusarlo

    opusarlo AK Subscriber Subscriber

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    It would be much easier to understand my motives after you listen to Widor's concerto 6 in G minor for pipe organ. I recommend you listen to Jan Kraybill's performance. Listen to it between 100 and 110/115 dB. I have extra horns (Altec 508 B) on top of my Cornwalls just because the pipe organ destroys the highs in my Cornwalls when I crank it. I also have a modest stack of subwoofer repair receipts from my Cornwall subs because pipe organ also eviscerates Cornwall subs. Pipe organ music is quite literally a music of mass destruction if you do not tweak your system just for it. This is why I am going with Maggies and 2 infinite baffle subs along with a DAC and DSP.
     
  20. opusarlo

    opusarlo AK Subscriber Subscriber

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    I sincerely prefer the hidden gems. For instance, Coopersville Christian Reformed church has an amazing pipe organ of 1700 pipes. There is also St. Paul's Episcopal organ (muskegon) with 3000 pipes...what a beast...I tend to stay away from mainstream organs. Thank you for asking. Do you play? Also, have you been to the house on 3rd street that has an entire organ installed in it?
     

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