Power Amp

Discussion in 'Mixing & Song Critique' started by The_Red_Fool, Apr 8, 2005.

  1. The_Red_Fool

    The_Red_Fool Guest

    Ok, my band just got some new speakers for our system. They have dual 15s and a horn, and they both max out at 700 watts, so 1400 watts total and operate at 8 ohms. Now we're looking at power amps but don't know which ones to go for. Any suggestions?
  2. Kev

    Kev Well-Known Member

    Nov 13, 2001
    Two 15's at 8 ohms ... sure there aren't 4 ohm speakers ??
    ... each drive is 8 ohms and paralleled to make 4 ohm.

    Full range or bi-amped ?

    An amp with more than 100 volt rails and current capability to put put big power into a 2 ohm load.
    somthing like 600 at 8 and then 1000 at 4 and as high as possible into 2 ... 14/1500 into 2.
    BOTH sides driven at the same time ... many 600 Watt amps just wont do this.

    Would be nice to know exactly what these speakers are so a more informed answer can be given.

    If you have a 1400 W into 8 both sides driven ... :shock:
    and if it can near double into 4 .... :shock: :shock:

    it's too big !!

    give it to me ... 8)
  3. anonymous

    anonymous Guests

    Feb 10, 2001
    Yeah, it would help to know the brand of speakers and of course the cost range you are looking for.
    I had a QSC a few years back, I paid like $1300 or $1400 for it, and it was 3000 WATTS. :eek:
    It was a damn good power amp. I sold it years later to some guy who owned a club downtown, It was the only amp he needed to power the whole club.
  4. The_Red_Fool

    The_Red_Fool Guest

    ok here's all the info from where i got them

    RMS Power - 350 watts rms

    Peak - 700 watts




    Woofer: 50oz. magnet, 2" kapton voice coil, stamp frame basket

    Horn: 5"x15" braced horn lens.
    Tweeters: 4 - 3.5" piezo bullet

    Cabinet: Precision tuned, 5/8" MDF, handsome black carpet, tough steel grills, bar handles, rugged plastic corners, input terminal with 1/4" input + 2 gold plated posts for bare wire leads/banana plugs, dual ports,
    50" tall x 20" wide x 17" deep.
    Weight: 75 LBS Ea.

    And a picture if that helps

  5. Kev

    Kev Well-Known Member

    Nov 13, 2001
    94 seems low ... two 15's in parallel ?
    but they should keep you happy for a while.

    As I said above
    and there will be a trade off between power and weight.
    The newer switchmode style amps and power supplies will make things lighter.

    The QSC mentioned above is a typical amp with good power.
    I don't think you need to go so big with the above speakers.

    450/500 @8 ... 1200 @2 both sides driven
  6. anonymous

    anonymous Guests

    Feb 10, 2001
    Look at those f----n monsters! :shock: Maybe you should do a google search for some of the more popular amps being used today. Once you find a brand that is (first) in your price range. 2ndly you like whatever about it (inputs, outputs, power switch on front or back, rack mountable or not, weight, look, or whatever)
    Then if you weren't sure which one after that we all could help you narrow it down some.
    Mackie makes power amps
    I already mentioned QSC
    Alesis still makes power amps (I have one that is smaller for reference monitors) it think its like 100Watts or something
    Anyone else want to chime in?
  7. Attitude

    Attitude Guest

    First, if an amp gives certain output into 8 Ohms, it will not give exactly twice as much into 4 Ohms. It will be much less than this due to the increased resistive losses and the way that power alters as the square of voltage.

    Second, those amps that consist of bipolar transistors running into 8 Ohm loads and operating class A or B (B just causes slightly more distortion but is way much more efficient than A) do cause the least distortion compared with any other amp running in any other mode and consisting of any other device no matter if it is JFET, MOSFET or whatsoever FET, or Tubes, which by the way is the worst.
  8. Kev

    Kev Well-Known Member

    Nov 13, 2001
    yes they can
    8) smug mode
    and just about double again into 2 ohms

    but then I built them to do that ... They will reliably run into just the speaker lead shorted at the speaker end. Round trip on the cables is less than 1 ohm and they will heat up very quickly.

    Amps are 105 volt rail with 10 up and 10 down of the old hitachi mosfets in the T03 package. ala ZPE and Perraux and Australian Monitor and David Tilbrook stuff of 80s.
    K56 / K176 was the pair I think.

    Massive VA rating on the power traffos ... one per channel and yes these amps are way too heavy for current mobile PA rigs ... so are now in permanent install.

    prototypes were built with 2 old 600VA traffos from the current amps at the time. Each traffo handled one rail and the secondaries were paralleled to carry the current and ended up more like servo amps than audio amps.

    todays prices are insane
    2SK176 + 2SJ56
    Manufacturer Hitachi
    Description Power Mosfet TO3
    Datasheet 200V 8A 125W
    Price US$60.00 per PAIR

    they were so cheap at the time.

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