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amps class a,b,c,d,what's the difference?

Discussion in 'Amps and Cabs [BG]' started by Loel, Jan 15, 2005.

  1. Loel

    Loel Blazin' Acadian

    Oct 31, 2004
    i here a lot about amps classified as a,b,c,d,is it wattage or ohms,size possibly quality of build;what's up with that.i tried a search but nothing came up!!
  2. DubDubs


    Aug 23, 2004
    Los Angeles
    It has to do with how the amp operates. it has nothing to do with wattage or class of build. It's the circut.
  3. NJL


    Apr 12, 2002
    San Antonio
    there may be a thread on this exact topic, it's very educational and well written, you may want to do a search

  4. Tim__x


    Aug 13, 2002
    Alberta, Canada

    Note that his discription of class-D is a little pessimistic, today class-D can be very high quality, as shown be EA, LCaudio, UcD, Bang&Olufsen, ect.
  5. Passinwind

    Passinwind I Know Nothing Supporting Member Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    There may actually be a few, plus there may be a FAQ on Talkbass which addresses lots of related stuff as well: http://www.talkbass.com/ampfaq/ :cool:
  6. Joe Beets

    Joe Beets Guest

    Nov 21, 2004
    I read all of that and now I'm more confused than ever. If I'm standing in the back of the room and my guitar player is thumping away on my bass, pretending like he knows how to play bass, and I am wearing a blindfold, will I be able to tell the difference between a PLX2402 and an RMX2450?? That is the question.
  7. Tim__x


    Aug 13, 2002
    Alberta, Canada
    Probably not, but I believe those are both class-H. :smug:
  8. Joe Beets

    Joe Beets Guest

    Nov 21, 2004
    The PLX weighs about 20 lbs. and the RMX feels like about 50 lbs.
  9. Tim__x


    Aug 13, 2002
    Alberta, Canada
    They are still both class-H, the difference is that the PLX has a switching power supply, and the RMX has a conventional 60hz supply.
  10. Loel

    Loel Blazin' Acadian

    Oct 31, 2004
    DUBDUBS:circutry yes makes sense.NJL:search i found nothing.TIM-X;his discription of d is pessimistic and dated.PASSINWIND;good link.MIKE DIMIN;EA's discription is indeed on the money.JOE BEETS;it's a long read. thanks to all for your input: for more on this check post yesterday titled;(amps the size of cigarette box...)by AnTzoR
  11. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    The descriptions in links are decent, if sometimes more confusing than helpful....

    Bottom line is that a class D amplifier draws much less power. The reason is that it wastes much less power. Most of the power drawn goes out to the speaker.

    That allows the amplifier itself to be smaller and weigh less. It also allows the power supply to be smaller and weigh less, for the same power output.


    We have two class-D units in the Ampeg line, the PB250 and the PB800.

    For instance, the PB800 produces 800W at 2 ohms. Three of the PB800 amplifier boards could be set on a regular sheet of paper, with lots of room left over. That is including their heatsinks.

    Complete with their heatsinks, they are about as thick as a hardback book.

    A normal amplifier of that power would require a heatsink of at least the volume of all 3 amplifiers put together, without including the actual amplifier.

    The average power draw of the entire PB800 when being played at loud volume can be less than just the idling power of an SVT with no signal. The power transformer is about 2/3 the weight it would have to be to power a "linear" type amplifier.

    As far as the distortion issues, there are several types of Class-D in terms of technical details. The high distortion complaint refers to one possible type of class-D unit, and to other technical limitations from 20+ years ago. Distortion is no longer a problem with the better types of class-D.

    I am personally acquainted with the owner of one of the esoteric high end audio companies. All their amplifiers are class-D. The amplifiers have been rated by independent reviewers as better sounding than many of the traditional "audiophile" brands such as Krell, and Mark Levinson, etc. So much for bad sound.
  12. Jeff Rowland?

    As in every kind of amp there are good ones and bad ones. I just got back from exhibiting at CES (high end audio) and I heard some class-D amps that sounded wonderful and some that sounded crap. Of course, I can say the same about the class-A amps I heard.