What is a Class H Amp?

Discussion in 'Amps, Pre-Pros & Receivers' started by 3db, Jan 21, 2008.

  1. 3db Audioholic Overlord

    3db
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    I looked at my technics receiver front facia and its says its using Class H amplifiers. I know and understand Class A, AB, C, and D. Whats this Class H stuff?
    3db,
  2. Joe Schmoe Audioholic Ninja

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    What is a class anything amp? I have never understood that terminology. I am also skeptical that it makes an audible difference (results are what matter, not how those results are achieved.)
  3. avaserfi Audioholic Ninja

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    This is an overview of amplifier types that Gene wrote a while ago. Class H is not included, but from my understanding class H is similar to class G which is a more efficient variation of class AB. The difference is that class H adds an infinite number of supply rails from my understanding.

    For more reading on the subject check out the Wiki.

    While my answer above will clear some things up for you the larger differences are in efficiency and heat production. Newer forms of amplification allow for lighter and more efficient amps that can produce as much pure power as older forms.
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  4. bandphan Banned

    bandphan
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    i guess from a manufacturing stand point it how it is achieved that gives us our end results.
  5. 3db Audioholic Overlord

    3db
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    Class of amplifiers refer to how a transistor amplifier is setup (from a voltage point of view) to amplify an incoming signal.

    I just wanted to know from a techical point of view what a class H amp is as I never studied this at school. If implemented properly, there would be no audible differences.

    Getting back technically, out of all of the classes of amplifiers mentioned, a class A amp would have the lowest distortion level present. Its also the most inefficient way of amplifying a signal.
    3db,
  6. fmw Audioholic Samurai

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    The amplifer classes relate to how output transistor biasing (feedback) is implemented. In the past, inefficient classes like A or even A/B were necessary to control distortion to inaudible levels. The other classes of amplifiers were available but not normally implemented in high fidelity sound reproduction. They were common in RF amplifiers, as an example.

    In recent years, they've made some technological improvements that have brought distortion under control with even the very efficient classes of amplification. As an example, my Pioneer receiver uses class D amps which are very efficient, producing a really cool running yet powerful output stage. But the distortion is still inaudible - just as low as if it were an A/B amp. D amps have been used in high fidelity sound applications for quite a while actually and are being used more and more.

    G and H are even more efficient than the D amps because they modulate the rail voltage making it "infinitely variable." The D amps are on and off devices. They are sometimes referred to as "switching amps." The G and H amps vary the voltage as the input signal rises and falls in level. The class A amps, in contrast, run flat out all the time. You can warm a room with a big one.

    The more efficient the amp, the less power it consumes, the less heat it generates, the smaller power supply it requires. The only problem has been that distortion rises with efficiency and other amplifier characteristics get worse for reproducing sound. Now that is becoming less and less of an issue with modern technology. I think amps will continue to become more efficient going forward and I would view it as a positive thing.
    fmw,
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  7. GlocksRock Audioholic Spartan

    GlocksRock
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    My Emotiva IPS-1 is a class H amp, and it runs cool as a cucumber, and it sounds awesome.
  8. Johnd Audioholic Samurai

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    I believe that is the main purpose of class H: its' efficiency. So it has a larger fanbase in commercial applications where uber power is required.

    And as a correction, as one member mistakenly (inadevertently) wrote, it does not have an "infinite number of supply rails."
  9. oldnickt Audiophyte

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    Class G and H

    From reading wikipedia it appears that class G refers to amps that switch their power rails to one of several values to improve efficiency. Class H has an infinitely variable power rail that is maintained a few volts above the signal. Both classes have been used with class AB, B and D amplifiers. In other words class G and H refers to the power rail strategy used, not the basic amplifier.
  10. Biggiesized Senior Audioholic

    Biggiesized
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    How long until a manufacturer builds an integrated receiver with a class H design?
  11. ski2xblack Audioholic General

    ski2xblack
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    I believe the NAD powerdrive curcuit is an example of class H (although never identified as such in their literature). The older Power Envelope circuit was class G, with only two rail voltages.

    Also, at least one of the discontinued Emotiva integrateds was class H, IIRC.
  12. ski2xblack Audioholic General

    ski2xblack
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    Class AB amps are indistinguishable provided they are operating WNL, and adequate to the task for all but the most discriminating of listeners, but class A is distinctly superior, more musical/realistic (assuming that is the result you are shooting for). Unfortunately, outside of DIY tube amps, almost all class A amps are outrageously expensive.
  13. TLS Guy Audioholic Overlord

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    They sound like class AB amps, which they are, but vary the rail voltage to load, so the manufacturer can skimp on components and claim to be "green". The big problem with those amps is reliability. H and G amps are not as reliable as other classes and are hard to fix. I would never ever get involved with one.
  14. Lordoftherings Banned

    Lordoftherings
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    Different class of amps for different class of people.

    I believe* that some models from Panasonic, Technics, Kenwood and JVC receivers used
    Class H and G amp designs. :eek:

    That might be a good indicator. ;) (Just like TLS Guy is saying.)

    * By the way, it is more than just a belief, I think it's a fact. ;)

    Me, I'll stick with a good Class A/B amp design. :)

    Bob
  15. mtrycrafts Audioholic Slumlord

    mtrycrafts
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    This might help you out:D

    http://en.wikipedia.org/wiki/Electronic_amplifier

    Google is our friend:D
  16. Lordoftherings Banned

    Lordoftherings
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    Google.

    That is a fact. ;)
  17. WmAx Audioholic Samurai

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    Class AB amps(assuming no defects or stupid design choices) are absolutely transparent, regardless of the 'discriminating listener', and this includes the more efficient variations such as H(when executed properly). The only difference perceived would be completely imagined. There is [absolutely] zero credible evidence to suggest otherwise. Audiophile hyperbole is not credible evidence.

    Class A is not superior in the real world. They waste energy(excessively) and provide nothing substantial in return for this. In addition, the best measuring amplifiers have actually been AB. Refer to the high end Halcros, which pretty much measure superior in every way to everything else(distortion so low in level in every way that the best measurement gear is near it's limit of resolution during analysis). Now, this is overkill, but it is a point that I refer to, as I am not aware of a class A amp that matches these examples.

    -Chris
    WmAx,
  18. ski2xblack Audioholic General

    ski2xblack
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    Chris, I would love to take you blindfolded through the RMAF and see just which systems sound the best to you. Lots of class A stuff at that event. And, the horror, tubes! (Perhaps you could point out the error of their ways and sell some behringer stuff to them to get them on the right path.)

    I actually think anyone interested in good sound should attend an audio fest, to get exposed to stuff you won't find at your local hifi shop. It would be a good place to compare different amp classes, as they are all present.
  19. WmAx Audioholic Samurai

    WmAx
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    The only thing a blindfolded positive I.D. would confirm is substantial measurable difference. Which, I would not doubt some of those amps have measurable 'problems'.

    As for good audio. I can assure you, I have experience with extreme high fidelity playback systems.

    I have been invited prior to the RMAF, along with full provided room and board. However, it is not in my interest to argue all day long at such an event(which is exactly what would happen).

    The only reason I can put up with the loonies at large high-end headphone meets, is because it is otherwise very difficult to find a suitable collection of high-end phones to audition for my future purchase considerations. But there is nothing at the RMAF that would benefit me enough to hold my tongue. :)

    -Chris
    WmAx,
  20. mtrycrafts Audioholic Slumlord

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    Probably not a good place at all unless a specific room is set aside and the DBT is properly conducted there. But, as Chris indicated, unless the design is euphonic, audible differences between classes are illusory at best;):D

    Otherwise, this paper would have had a different outcome.;)
    David Rich and Peter Aczel, 'Topological Analysis of Consumer Audio Electronics: Another Approach to Show that Modern Audio Electronics are Acoustically Transparent,' 99 AES Convention, 1995, Print #4053.

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