Why don't Aragon, Bryston, Rotel, Parasound, Proceed, etc make Class G amps?

Discussion in 'Archived Threads 2001-2004' started by Ricky T, Feb 19, 2003.

  1. Ricky T

    Ricky T Supporting Actor

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    Does anyone beside me wonder why just about every major amp manufacturer doesn't use Class G designs in their amps? Most amps are A/B with varying bias in pure Class A. These new Outlaw/NHT 200 watt monoblocks go from A/B to G at 80 watts. So above 80 watts, you are listening to G. If Class G sounded better than A/B, wouldn't companies like Bryston, Aragon, Classe, etc implement it? Some of their amps retail $800-1000+ PER channel, so sound quality is key for survival of the fittest...yet none of their amps have Class G designs.
     
  2. Kevin T

    Kevin T Screenwriter

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    might wanna look at the definitions of each:

    Class A operation is where both devices conduct continuously for the entire cycle of signal swing, or the bias current flows in the output devices at all times. The key ingredient of class A operation is that both devices are always on. There is no condition where one or the other is turned off. Because of this, class A amplifiers are single-ended designs with only one type polarityoutput devices. Class A is the most inefficient of all power amplifier designs, averaging only around 20%. Because of this, class A amplifiers are large, heavy and run very hot. All this is due to the amplifier constantly operating at full power.The positive effect of all this is that class A designs are inherently the most linear, with the least amount of distortion.

    Class AB operation allows both devices to be on at the same time (like in class A), but just barely. The output bias is set so that current flows in a specific output device appreciably more than a half cycle but less than the entire cycle. That is, only a small amount of current is allowed to flow through both devices, unlike the complete load current of class A designs, but enough to keep each device operating so they respond instantly to input voltage demands. Thus the inherent non-linearity of class B designs is eliminated, without the gross inefficiencies of the class A design. It is this combination of good efficiency (around 50%) with excellent linearity that makes class AB the most popular audio amplifier design.

    Class G operation involves changing the power supply voltage from a lower level to a higher level when larger output swings are required. There have been several ways to do this. The simplest involves a single class AB output stage that is connected to two power supply rails by a diode, or a transistor switch. The design is such that for most musical program material, the output stage is connected to the lower supply voltage, and automatically switches to the higher rails for large signal peaks. Another approach uses two class AB output stages, each connected to a different power supply voltage, with the magnitude of the input signal determining the signal path. Using two power supplies improves efficiency enough to allow significantly more power for a given size and weight. Class G is becoming common for pro audio designs.

    kevin t
     
  3. Kevin C Brown

    Kevin C Brown Producer

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    I don't know nothing, but I do know this: [​IMG]

    80 watts in a home environment is a lot. I'd bet it would be rare to see this listening to music, but maybe more often listening/watching DVDs. But of course depends on room size, speaker efficiency, volume levels, etc.

    My impression is, class G is relatively new, so maybe the other manufacturers haven't gotten there yet. ?

    Plus, I think Outlaw wanted to do a space saving design, so maybe that required a different class for higher output levels.

    And obviously, the Outlaw mono block does not cost $1000/channel, so it is a more cost effective design.

    But it is a good question.

    Unfortunately, only Stereophile does the in depth type measurements that Audio amd Stereo Review used to do, so maybe we can hope they test one someday.
     
  4. Ricky T

    Ricky T Supporting Actor

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    A couple of responses from my thread on AVS.

    "NAD had implemented class-G power supply in their amps, starting with the 2200PE, which had great headroom for inordinarily long duration. But some people felt that class-G power supply was detrimental to the sound."

    Therefore, Class G is not new as the 2200PE is at least 10 years old.


    From Paul Scarpelli
    Director of Sales & Marketing, Triad Speakers, Inc.
    in answer to my question:

    If Class G sounded better than A/B, wouldn't companies like Bryston, Aragon, Classe, etc implement it?

    "If it did...they would. It doesn't...they don't."

    And yes, 80 watts is alot. Does that mean that you would view these as 80 watt monoblocks?
     
  5. Kevin C Brown

    Kevin C Brown Producer

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    Ricky- Cool, so it gets back again to performance for cost.

    Well, I guess you could say they are 80 W class A/B monoblocks... [​IMG]

    And Outlaw was started with some dudes from NAD, so that makes sense...
     

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