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Thread: new class D amps

  1. #1
    Senior Member
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    Apr 2005

    new class D amps

    Hello. any one knows any thing about class D amps. I just might be geting old and behind time. class D dont have the power supply or caps , as the class a-b amps. how can it produce deep bass at low or high volume. also what does the mids and highs sound like. and my last question,did the high end audio companies charges us a bunch of money for these heavy as hell power amps with these huge transformer and caps-vs companies like crown -qsc-yamaha for a long time been selling high power amps that weighs around 20 pounds and sound just as good as high end amps.

  2. #2
    Senior Member Jan Daugaard's Avatar
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    Apr 2003

    Class D

    Hi Gene,

    Wikipedia is good for an article on class D amplifiers, too:

    Using Google to search for "class D", you will find many references to manufacturers of class D amplifiers, including

    which have had excellent reviews in Danish "High Fidelity" (unrelated to the American magazine by the same name).

    Jan D

  3. #3
    Senior Member Baron030's Avatar
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    Feb 2005
    Chicago, Illinois

    Class-D & Class-I

    After doing a Google search on Class-D amplifiers, I found a nice little educational PDF file. It's not a bad description of how Class-D amplifiers work, just don't let the math scare you.

    All Class D amplifiers work by some form of switching (Pulse Width Modulation). Depending on the sampling rate and the accuracy of the Pulse Width Modulation circuit, sound quality can vary a lot.
    For example, A Class-D amplifiers designed for car audio applications have a low sampling rate and can not reproduce frequencies above 200 Hz. without excessive distortion. That's why they are used for sub-woofers only. And they also have a very low damping factor, which can lead to a very "Boomy" bass sound.

    As a work around for some of the Class D limitations, Crown Audio came up with an interleaved Class-D amplifier design. They call it a Class-I amplifier or balanced current drive. It has twice the sampling rate of a typical Class-D amplifier and a very high damping factor.

    if you go to and down load the "Original (1996) White paper on Class-I by Gerald Stanley" PDF file. You can get a full description of how their Class-I switching amplifier works. The Crown K-Series was the first to use this interleaved Class D amplifier design and they have excellent sound quality.

    Concerning amplifier power supplies, a lot of the technology that was first developed for personal computers is now making its way into other products like audio amplifier. For Example, your computer has at least a 300-Watt switching power supply and yet it weights only 1 or 2 lbs. If your computer had a conventional power supply, the transformer alone would have to weigh in at about 25 or 30 pounds. Modern switching power supplies do not need large capacitors or chokes, to filter out the 60Hz hum. And I know this may sound strange. But, solid-state integrated circuits are now cheaper than the heavy copper and iron transformers and chokes that we all grew up with.


  4. #4
    Senior Member Ducatista47's Avatar
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    Jul 2005
    Peoria, Illinois


    The link at the bottom of this page has some forum member's takes on the designs.

    Information is not Knowledge; Knowledge is not Wisdom
    Too many audiophiles listen with their eyes instead of their ears

  5. #5
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    Apr 2005
    Thanks for the input

  6. #6
    Senior Member gerard's Avatar
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    Sep 2004
    Casablanca - Morocco

    I open already on thread on the nuforce amplifier which seems to be among the best amplifier available ( see ) .

    I never had the chance to test the monoblock ref 8 and 9 , looks like switching class D amplifier .

    I am still looking for a test report from a jbl forum user so I would be really able to trust if those amps are so good .


  7. #7

    Class D Amps Reply

    The biggest issues are how high is the sampling frequency as stated by another forum member.
    IE Is the amp trully rated at full power for a full bandwidth.
    In the old days power rating was always stated as xx watts RMS per channel from 20HZ ro 20Khz . Or full power bandwidth.
    What this means is that the amplifier will produce at least xx watts RMS per channel at all frequencies from 20Hz to 20Khz .
    The IEC specification is even better , the IEC spec (which most manufacturers don't or won't list is the continous amount of power the
    amp will drive at all frequencies driven typically using pink noise.
    Class D or switching amps in the past tended to sound thin with no depth , mostly due to phase distortion and zero crossing distortion.
    But many of the chip manufacturers are design much better Pulse Width Modulation translators using better PLL's and controls circuits inside the
    chips. So the newer ones tend to sound much better . Although no one that I know of produces a high end CLass D amplifier .
    The main benefit of Class D is size and efficiency , they are very efficient when compared to Class A/B, C or H . which are the standard topologies.
    The efficiency also creates much less heat as each transistor is"ON" for significantly smaller part of the waveform.
    If you want decent sound at a good price with higher power , most of the commercial Class A/B MosFet amps coming out now are quite good sounding , but tubes still have a warmth that is hard to beat.

  8. #8
    Senior Señor boputnam's Avatar
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    Apr 2003
    northern california
    I've just started working with a pile of the Lab Gruppen fP's and have to say I am very impressed. I had run across them in my working with one of the major tour sound support companies in the Bay Area, who had moved to them away from Crown. They are not going back...

    The fP series sound phenomenal. When I get the install done, there will be a full report, but initial impressions are "stunned". :shock:

    Here's Lab Gruppen's approach to Class D:
    Attached Images Attached Images  

    "Indeed, not!!"

  9. #9

    D CLass Amps

    Quote Originally Posted by boputnam View Post
    I've just started working with a pile of the Lab Gruppen fP's and have to say I am very impressed. I had run across them in my working with one of the major tour sound support companies in the Bay Area, who had moved to them away from Crown. They are not going back...

    The fP series sound phenomenal. When I get the install done, there will be a full report, but initial impressions are "stunned". :shock:
    Thanks ; I've heard of these guys , and apparently there are some decent reviews , I would still like to see an IEC spec for these amps . are they really capable of driving all frequencies simultaniously without running out of juice. But then again if your guys are running it for a mains touring PA application , then they've got to be able to perform , driving 18's with big coils is no mean feat , I've seen many a blown up amp , cause of poor power handling , although thats never been a problem with Crowns in a live situation.

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