Lumin AMP (Class AB) - Page 3
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  1. #21
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    Re: Lumin AMP (Class AB)

    Quote Originally Posted by Mike View Post
    I’m going to state at the outset, I frankly don’t think there is an amp better than the Luxman M900u at maybe 3 times it’s cost or more. When I read Doug Schneider call the Luxman M900u the best amp he had ever heard, I thought he was on crack. Seriously I did. When I first got one in the store, I was floored and I certainly don’t think he’s on crack now! [...]
    That's high praise Mike. Do you find that they sound best when used with the matching Luxman pre-amp, the C900u or is the assessment with a different pre-amp?
    Borresen Acoustics ApS Model 01 Compact monitor loudspeakers, Audio Video Manufaktur GmbH (AVM) Inspiration amplifier & streamer, Innuos Zen MKII music server, Ansuz Acoustics cables & accessories. Please visit my system thread hosted on Audioshark for more details.

  2. #22
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    Re: Lumin AMP (Class AB)

    Quote Originally Posted by BlueFox View Post
    Does class AB mean it operates in class A up to some point, and then goes into class B after tha point? If so, how far into A does it operate?
    The strict definition of what a class AB amplifier is does not mean that it operates in class A up to a certain point and then transitions into class AB. Class AB means the the two transistors in the simplest of output configurations conduct for a little more than 180 degrees of the input wave form but much less than the full 360 degrees of conduction in a class A amp. What this does is get rid of cross over distortion and improves efficiency over that of a pure class A amp.

    I have heard of amplifiers designs that operate up to class A to a certain point and then transition to another class of operation but this is not the strict definition of what a class AB amp is.

    Wyklie can correct me if I am wrong and/or let us know what Lumin's definition of what class AB is to their design engineers.

  3. #23
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    Re: Lumin AMP (Class AB)

    correction... class A amps do not have cross-over distortion

  4. #24
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    Re: Lumin AMP (Class AB)

    Quote Originally Posted by dznutz View Post
    correction... class A amps do not have cross-over distortion
    Right you are. What I was trying to say was that, with a complimentary pair of transistors operating in class B, there is significant cross over distortion when one xisitor turns off and the other one turns on. The class AB biasing works to almost entirely minimize this distortion hence the naming convention class AB.

  5. #25
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    Re: Lumin AMP (Class AB)

    Quote Originally Posted by BlueSky View Post
    Right you are. What I was trying to say was that, with a complimentary pair of transistors operating in class B, there is significant cross over distortion when one xisitor turns off and the other one turns on. The class AB biasing works to almost entirely minimize this distortion hence the naming convention class AB.
    Think about the signal is the upper half and lower half. p and n channel transistors repsosible for upper and lower part of the signal, Pure B, is no overlapping, AB is where the signal has a slight overlapping. Where class A is complete overlapping. The overlapping range is closely related to the output magnitude of the signal. So for the Lumin amp, it is true to say it is pure class a up to a certain point, and class AB for the rest of the output power.

    I am one of the designer behind the lumin amp and the sound tuning engineer for the X1.

    A.

  6. Thanks audio.bill, FDPDK, NekoAudio thanked for this post
  7. #26
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    Re: Lumin AMP (Class AB)

    Quote Originally Posted by BlueSky View Post
    Wklie can correct me if I am wrong and/or let us know what Lumin's definition of what class AB is to their design engineers.
    I'll leave questions or support requests on Lumin AMP to @lscangus.
    Peter Lie
    LUMIN Firmware Lead

  8. #27
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    Re: Lumin AMP (Class AB)

    Quote Originally Posted by lscangus View Post
    Think about the signal is the upper half and lower half. p and n channel transistors repsosible for upper and lower part of the signal, Pure B, is no overlapping, AB is where the signal has a slight overlapping. Where class A is complete overlapping. The overlapping range is closely related to the output magnitude of the signal. So for the Lumin amp, it is true to say it is pure class a up to a certain point, and class AB for the rest of the output power.


    I am one of the designer behind the lumin amp and the sound tuning engineer for the X1.

    A.
    Iscangus, thanks so much for the response and I thank you especially for the the audio magic you have created with the tuning of the Lumin X1's sound!

    A class A amplifier is an amplifier in which the output device(s) are biased in the middle of their "load lines" and conduct for the full cycle of the input signal so they never have to cut off and transition to a complementary transistor that would be typical in a class B amplifier to handle the other phase of the input signal. So, if I am to understand you correctly, in the Lumin implementation of it's version of class AB, one of the devices (P or N) at low signal levels is biased so that that single device handles all 360 degrees of the input? If that understanding is not the case and both the P and the N devices are always conducting for at least a portion of the input waveform regardless of how small the input signal is, then I would still say that the amplifier never really enters into a class A mode of operation.

    Again, my thinking could be flawed and I will seek to learn more about it just to satisfy my own understanding.

    Thanks again!

    Joe

 

 
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