Class A/B vs Class D, is there an audible difference

Discussion in 'AV Receivers / Processors / Amps' started by Tony V., Feb 10, 2018.

  1. Tony V.

    Tony V. Moderator
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    Just recently installed a new Onkyo receiver with class D3 amps.
    After a few weeks of use I can say that the sound quality of the D3 amps sound the same as my previous AB class receivers did. I know there is resistance from many old school users but is this justified?

    I've seen comments that class D frequency response can not go as low as A/B switching amps but if that was true then why have many high end sub manufacturers been using class D for some time now. I've also read some say class D is noisy but I can't hear a sound out of my speakers unless I crank the volume well past any reasonable levels and sound quality as I said earlier is as good as I've ever heard.
    Thoughts?
     
    #1 Tony V., Feb 10, 2018
    Last edited: Feb 10, 2018
  2. GFOviedo

    GFOviedo Senior Member

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    My previous Pioneer received had class D Amps, and I did not notice any audible difference with my Denon either. The one thing I noticed was that the Pioneer ran cooler compared to my Denon, Marantz and Onkyo receivers. I'm glad Onkyo made the move to class D amps since Onkyo ran as hot at my fire chimney.
     
  3. Todd Anderson

    Todd Anderson News Editor / Reviewer/ Senior Admin
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    I'm onboard with both of you guys. I can't hear a difference between them either. Perhaps once correction is applied... but not straight when considering equal output.

    Now, if you were attempting to power mega-highend speakers? Perhaps a difference would be audible.
     
  4. leecreek

    leecreek Active Member

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  5. AudioThesis

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    When it comes to solid state I prefer A/B over all others. While Class A is supposedly top dog, I don't like the size of the images I get from those I've tried. The image sounds like its the width of a pencil, regardless of what the source of the sound is. With Class D, I find the 'hifi' amps to have a very artificial sound to them, especially in the bass. It is so controlled that it really doesn't sound natural in any way. The sound is rather lifeless as well. I've heard D can be done well, but I haven't heard it yet.

    I will say that the Pioneer SC amplifiers seemed to have gotten some good juju. They are among the better units I've heard, especially for a receiver. They still don't compare to a good A/B in my opinion, but they are great receivers with power for just about any speaker you want. I wish all receivers would jump on the Class D technology as it can only be a positive for everyone.
     
  6. GFOviedo

    GFOviedo Senior Member

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    I agree with you. I think once you go to the "really expensive" and "high end" audio, you will definitely hear a difference depending on your source as well. I did hear a definite difference when I went from my HTIB Onkyo to my Chane speakers, Denon AVR and Emotive amp specially for 2.1 music. If I had a lot of $$$, then I would definitely dedicate one room for movies and another room for music. That's probably something I will never have a chance to do.
     
  7. ddude003

    ddude003 Active Member

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    I am not real clear on the goal of a class D amp... I think they sound pretty good for low frequencies (read tight/control) and some what dry or un-life-like in the higher frequencies... I like the sound and sweetness/warmth of class A and A/B amps... And the right tubes in the mix can make a huge difference in performance(read soundstage/presence)... I am also a believer in hurling watts of power thru lots of copper sounds the best... It seems to knock the edges off...
     
  8. Tony V.

    Tony V. Moderator
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    Class D amps are far more efficient and run much cooler than A or A/B
     
  9. ddude003

    ddude003 Active Member

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    Efficiency at the cost of quality of sound it seems... After review of a few design papers it appears to me that a typical class D amp (cut to chase) takes an analogue signal, converts it to a digital signal, adds gain, then filters it back to an analogue signal again... Several gremlins creep in caused by many tesla, maxwell and faraday issues...
     
  10. Tony V.

    Tony V. Moderator
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    I dont know if I can agree that quality is lost as so far I am very impressed with the Class D3 amps I have in my Onkyo and believe me I was very hesitant on getting it because of the mixed reviews.
     
  11. Todd Anderson

    Todd Anderson News Editor / Reviewer/ Senior Admin
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    I agree with the latter ... more power always seems to sound better!
     
  12. AudiocRaver

    AudiocRaver Senior Admin
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    I have not been able to hear a difference that was "digital" vs "non-digital." When I have been able to tell a difference between two amps, and had the opportunity to try to explain it, there has been a measurable spec or characteristic that did so. I am a believer that audible differences between amps can be measured if we know what to look for and how to measure it, although there are certain to be exceptions. So I guess I will enter my plea as "there is no digital sound," just audible, explainable differences between amps.
     
  13. Sonnie

    Sonnie Senior Admin
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    This is no doubt a difference in heat between A and A/B. We thought something was wrong with one of my Emotiva XPA-1 monoblocks, but discovered one was set to A, and it was extremely warm. Not warm sounding... no... warm to the touch. Can't say the right speaker was any warmer sounding than the left. :bigsmile:
     
  14. Matthew J Poes

    Matthew J Poes Staff Writer
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    I'm with you Wayne. The reason a lot of Class D amplifiers sounded bad in the past (and some still do) are due to very measurable problems. The most common are current delivery and high frequency oscillation.

    Another problem has been that the filter coming after the feedback and causing instability and response variation with load.

    There are a number of "class D" amps such as those from Hypex, ICEpower, and THX which offer near perfect measured performance and totally neutral sound. They even have been noted for their tube like sound and there are measurable reasons why that might be. These amps have nearly no distortion including switching distortion and as a result do not suffer a rise in high order distortion that most amps with a lot of negative feedback would have. Most tube amps have very little negative feedback and so whole they have higher overall distortion, it's largely benign 2nd order with very low high order. Often lower than their solid state equivalents. They are also often either class A or biases such that they have pretty low zero switching distortion.

    I personally love Hypex amplifiers and use them in my system.
     
  15. Matthew J Poes

    Matthew J Poes Staff Writer
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    Pioneer has had some magic amps for a while for some reason. They had some receivers for a while using what looked like a cheap basic chip amp but both measured and sounded really decent. Not Krell amazing, but very good for sure. The SC series used icepower and D3 which was pioneers own class D design. The story I heard was that their engineers were asked to benchmark the icepower models and better them. I imagine it was a cost savings choice as well, but if they could better the performance for less, that's not so bad.

    I agree that receivers should all go Class D but only if it's of the Ilk of ICEpower, D3, Hypex, THX AAA, etc. There are still a lot of class D amps out there with compromised performance. I'd rather not see those proliferate.
     
  16. AudioThesis

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    I disagree with your first post Matt, especially the comment about D sounding like tubes. Never have I thought that. I've still yet to hear Class D sound natural, but I have heard several A/B amps deliver in that category. The better Class D amps I've heard get the tone right, but nothing about the presentation is correct. Your mileage may obviously vary. :)
     
  17. Matthew J Poes

    Matthew J Poes Staff Writer
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    Have you heard the Theta Hypex NCORE amps?
    http://thetadigital.com/prometheus_amplifier_info.shtml

    These use the NCORE modules with a really good power supply and front end/input stage. If you haven't, they just might change your mind about Class D.

    I'm not unique in thinking Class D sounds tube like, but as you say, your mileage may vary. Take a listen to the Theta and see if you don't at least find a better overall presentation.

    These Nord amplifiers sound nice as well:
    https://www.nordacoustics.co.uk/nord-one-hypex-nc500-se-stereo
    Based on the same family of modules, though a bit more off the shelf. These are the amps that got me to built my NCORE NC400's.
     
  18. tesseract

    tesseract Senior Admin
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    Yes, I noticed a L/R heat disparity. I can not say I heard a difference.
     
  19. Matthew J Poes

    Matthew J Poes Staff Writer
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    Hah, you guys are too much. Having never seen any deep inspection into this concept I cannot say too much, but I read an article that talked about the recent rise in amplifiers with class A switches. What these do are to raise the bias voltage to a high enough level to force the amp to operate into Class A up to a higher wattage. They are still Class A/B amps, but operating as Class A into the 25, 50, sometimes even 100+ watt range. The author was an electronic circuit expert who designed amplifiers for the audio industry and he felt that these are compromised circuits in this setup and actually sound worse (if different at all). He really felt such amps should be left in their class A/B setting. That to really hear the difference a true Class A amp makes, you need an amplifier designed as a Class A amplifier outright, something more like the Pass amplifiers. There only real advantage is a reduction in switching distortion which would only be audible at very low levels of information.
     

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