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QSC Powerlight query ... Bob, you around?

Discussion in 'Amps and Cabs [BG]' started by velvetphil, Oct 27, 2006.

  1. So I'm considering picking up a QSC PLX 1602 or 3402 to use with my Acme Low B2 (running in stereo or bridged mono, depending on which model I go with). Andy over at Acme seems to think that in terms of consistent DC current, there's no substitue for either enormously heavy capacitors or an enormously heavy transformer. Anyone have any opinions on the PLX's performance in this area? Power drops, "brownouts", etc.? Bob, what's the theory behind the PLX's output system, and how does it address this issue?
  2. aniki


    Aug 12, 2005
  3. Hmmm, very interesting stuff, especially Jim Bergantino's posts. I will take this into consideration!
  4. msquared


    Sep 19, 2004
    Kansas City
    FWIW, I run a PLX 1804 into one of Andy's cabs and it sounds great. Just because it "sounds better" with a heavy amp doesn't mean a light amp is at all undesirable.
  5. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Yep, and maybe also bear in mind that Mr Bergantino thinks a (specific) lightweight amp is acceptable to be built into his flagship powered cabs.
  6. Bob Lee (QSC)

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

    Jul 3, 2001
    Santa Ana, Calif.
    Former Technical Communications Developer, QSC Audio
    For 50 or 60 Hz power conversion, you need a big transformer, to avoid core saturation, and big capacitors. For higher frequency power conversion, the saturation problem diminishes and you can convert power with transformers that aren't as big, and it will still have big capacitors on the line-frequency side.

    Power drops and brownouts will affect power amps' maximum output capacity whether they have line frequency power supplies or switch-mode supplies, unless they are regulated.

    Keep in mind that if someone tells you he can't fly an airplane and therefore airplanes can't fly, you can look around and see that other people can fly planes.
  7. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    I read the second thread, which I must have missed back when it came out.....

    As you may have noticed from the first link, I believe that heavy iron MAY very well sound better and more powerful/have more "slam", etc for amps of equal nominal power. I mentioned a number of reasons WHY that can be, but not a complete list of them.

    I do NOT agree with Mr Bergantino that it HAS to be so.... That is a blanket sort of statement that doesn't make sense if you know what the variables are. I do not know who the "industry insider" he mentioned is, but I question their motivations, since I do not regard this as a real "technology" issue.

    It is perfectly possible, today, to design and make an SMPS amplifier that has the same audible power capability as a premium heavy iron unit of the same nominal power rating.

    And, AN IMPORTANT POINT..... NOT even every CONVENTIONAL amplifier has the power characteristics that are being discussed.

    There are some amplifiers of conventional design which are KNOWN to have much more "oomph" than most. You would typically find them running the subs in touring setups, with others used for the rest of the setup.

    Those units had EVEN HEAVIER iron than usual, and very large filter capacitors. Larger than average, much larger than the minimum requirements to "function".

    Most units have lighter components, designed to cover average requirements. it's a cost thing.

    OK, among SMPS type amplifiers..... It is also very common in SMPS units to have the design "thinned and lightened"..... to where it covers the average requirements only. Just as among conventional amps, but more so, due to certain possible shortcuts that are somewhat unique to SMPS, and cannot be done with iron transfomers.

    Those shortcuts DO in fact have the exact effect Jim B mentions.... And, most SMPS amplifiers have some or all of those shortcuts taken. They DO reduce cost, and they are nominally "permissible" due to certain characteristics of an SMPS.

    But, if a design were done with the SMPS made to satisfy a more "industrial" duty cycle, and with a couple other minor changes, it could be every bit as "slammy" as any iron transformer unit, but still a lot lighter. It would be more expensive..... but then a heavier duty iron power supply is also more expensive. The parts are not free.

    A unit specifically made to cover audio requirements might be different, and not quite as costly as an "industrial" rated unit..... and yet could be BETTER at covering audio needs.

    There are not very many, if any, units that I know of that are really done that way.

    But, far from being a technology dependent matter, it is really more of an implementation matter, in my opinion.

    That doesn't change your buying decision today...... this is really more a "futurist" discussion.
  8. BigMikeW

    BigMikeW Inactive

    May 25, 2005
    Nashville, TN.
    Banned by TB Administration for refusal to account for funds
    I love that post of Jim's! And then, he came out with the IP series using SpeakerPowers digital, SMPS power amp.
  9. lowmid1


    Aug 16, 2002
    Baltimore, MD
  10. BigMikeW

    BigMikeW Inactive

    May 25, 2005
    Nashville, TN.
    Banned by TB Administration for refusal to account for funds
    Not a bag on Jim at all. Just seems like a quick turn around in beliefs about that technology.
  11. jerry

    jerry Too old for a hiptrip Gold Supporting Member

    Dec 13, 1999
    When I used a pair of Andy's fine B2's, I powered them with a PLX2402......sounded great, to me anyway.

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