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Power Amp Classes/Terminology: What Does It All Mean To The Average Bassist?

Discussion in 'Amps and Cabs [BG]' started by ebozzz, Aug 30, 2002.


  1. ebozzz

    ebozzz Supporting Member

    May 17, 2001
    Denver, Colorado
    I just read an older article again entitled, Power Amps: Terminology, that was in the February '02 issue of BP. Class A, B, AB, D, G, H and T.....Is one better for bass rigs than the other? How does the slew rate, damping factor and switching(power supply and on the output stage) affect the performance of the amps from these different stages?

    My power amp is a Class H variety with a switching power supply. It sounds great to me but I never considered any of the things that I listed above prior to making my decision. What factors should we look for regarding making a decision about a power amp?
     
  2. Ya!
    Could somebody explain why mesa/boogie's 360 watt m-pulse and edens 800 watt world tour both claim to peak at 1200 watts? Does this have to do with that power supply type, and if so why? I've always thought RMS ratings where supposed to be "root mean square"? If this is so, than boogie shouldn't peak at 1200W or it should be rated aprox 800W?:confused:
     
  3. See If we can't get a response;)
     
  4. Coming from a tech head: forget all the gibberish, go by your ears. It's what I always do.

    "If it sounds good, it is good" (Duke Ellington)
     
  5. virtual.ray

    virtual.ray

    Oct 25, 2000
    I've only ever used traditional (non switching) amps,so I can't comment there,but "slew rate" is basically how fast the amp responds to the signal it's getting at the input,so the faster it is,the greater the integrity of the original signal will be preserved.I guess this is even more important for slap style where the signal is real spikey.
    "Damping Factor" is basically how well the amp controls the movement of the speaker cones,especially important when a lot of low frequency information is present as in your average bass guitar.A high DF will result in greater clarity and intelligibility,a "tighter" sound.
     
  6. Mara

    Mara

    Jan 11, 2001
    Finland
    v.ray,

    What is "good" DF? I've been looking into the Phonic MAX2500 which DF is rated >300@8£[.

    http://www.phonic.com/spec_max.htm

    -Mara
     
  7. Matthias

    Matthias

    May 30, 2000
    Vienna, Austria
    Coming back to the thread title:
    "What does it all mean to the average bassist?"
    Nothing.
    Especially the Class A, D,... stuff. It just specifies how the amp is working, but is NOT related to quality - e.g. a class A amp is not better than a class D amp, just different.
    But as a 'user' of the amp you don't have to worry about that as long as you like the tone.
    Of cause there ARE differences in performance of different amps, but I doubt you can tell this just by reading the specs.

    With regard to Bob Lee (QSC) you also have to take the damping factor with a grain of salt. See his post in this thread:http://www.talkbass.com/forum/showt...page=20&highlight=damping factor&pagenumber=3

    Matthias
     
  8. ebozzz

    ebozzz Supporting Member

    May 17, 2001
    Denver, Colorado
    Hey, that's my thread Matthias! :) I guess I'm sort of asking if there is any information that a person can use to make a good amp choice if there is no possibility of trying that particular amp. Are there certain specs that would be more desired for bass? It doesn't sound like there is a method of using the specs in the selction process with any degree of success. I guess it's just a roll of the dice if you can't try it prior to buying. That Duke Ellington comment that Joris brought up is great and that's definitely the theory that I subscribe to. ;)
     
  9. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    Amplifier classes really just describe the operation of the output circuitry of the amp, the part that handles the power. Some types are inherently more efficient than others, some are easier to design well, and so on, but none are inherently good or bad for audio; it all depends on the design and how it's implemented.

    Specs like damping factor, as mentioned above are overrated. Slew rate is a pretty meaningless spec, because you want enough to deliver full power at the highest audio frequencies but not so much that the amp is unstable or susceptible to picking up RF interference. IOW, there's no "the more the better" concept with slew rate. But truthfully, I'd be greatly surprised if there's an amp on the market whose slew rate isn't high enough to put out full power at well beyond 20 kHz.