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Stewart World 1.2

Discussion in 'Amps and Cabs [BG]' started by RAT TAT TAT, Apr 25, 2006.

  1. ok, when they say that this amps max rating when ran mono bridged is 1200w @ 4ohms(http://www.stewartaudio.com/world12.html) are they measuring it differently then say ampeg would. for example.. the svt 4 pro is rated 1200w mono bridged at 4 ohms aswell... but at 4 ohms the svt 4 runs 2 channels of 490 watts as opposed to stewart worlds 350 x 2 @ 4 ohms. why on gods green earth would someone carry around an ampeg svt 4 pro instead of a stewart world 1.2 and an ampeg preamp if they have the same power and sound? please help me understand haha. thanks in advance.
  2. joelb79


    Mar 22, 2006
    Lansing, Michigan
    the simple answer is ... weight.

    SVT-4Pro = 42 lbs

    SVT-Preamp + Stewart 1.2 = 18Lbs.

    When you bridge the amp, you will not be able to tell the difference. Only your back when you haul the amp off you 2 410's will. Rarely will you EVER use more than 350 watts, only your transients (slaps and heavy plucks) will take more than that. and those should be very short lived. The amplifier section of a quality mosfet amp should sound no different than another brand. But i dont own a svt-4 nor a stewart 1.2, but im going to guess the stewart has more honest power specifications, and sounds cleaner in the first place.

    There's the short answer.
  3. KJung

    KJung Supporting Member

    I can totally understand why someone would carry a more 'lead sled' heavy amp versus, for example, the Stewart. It's the same reason that my 7 pound 1,200 watt Walter Woods mostly stays at home now, and my 500 watt 16 pound Thunderfunk goes to most gigs. While 'a watt is a watt', the delivery of those watts throughout the entire frequency range is not always the same. Most 'traditional' amps (i.e., those with a big, heavy, linear power supply) that I've played through have much more punch and 'balls' than the two 'switching power supply amps' I've used (AI and WW).

    I find the Steward 1.2 less than impressive in this area also.

    That all being said, I've read many threads that seem to indicate that some of the newer, larger, two space PA type 'switching power amps' sound really nice, and I understand the larger Stewarts sound pretty good also.

    Just my 2 cents.
  4. Quadzilla

    Quadzilla Supporting Member

    I have a Stewart 1.6 (2U, 1600 watts) on it's way to me now. I'm going use it with my Ampeg SVP-Pro. I'll let you know how it works out.

    As for switching amps not delivering, I just did a large outdoor gig with my Aggie AG500 and Berg 610 this past Sunday. I actually had to turn down a few times. The Aggie/Berg rig MORE than delivered (500 watt switching amp).
  5. KJung

    KJung Supporting Member

    As far as I know, the Ag500 does not have a switching power supply (or else they are hiding it in that big linear transformer in the picture on the website:D ), and has a class A amp, not a class D... about as far away from 'digital' as you can get.
  6. vision

    vision It's all about the groove!

    Feb 25, 2005
    Ann Arbor, MI
    Endorsing Artist: MTD Basses, La Bella Strings, and 64 Audio IEMs
    +1...from the pic here, that definitely isn't a switching power supply.

  7. Quadzilla

    Quadzilla Supporting Member

    From the Bass Player mag review (pretty muchc a modified class D):

    The conventional class AB power amplifier is a tried-and-true design, but one that operates relatively inefficiently, producing enough
    excess heat to require noisy fans and large heat sinks, which add to an amplifier’s bulk. Class D amps are far more efficient. They
    produce power by switching transistors on and off at a high frequency using a process called Pulse Width Modulation. The AG 500 is
    like a Class D amp, but it utilizes switching technology developed by the Tripath Corporation. The Tripath power amp topology, named
    Class T, modulates the output using a proprietary module that purports to eliminate some of the weaknesses of Class D amps while
    maintaining the efficiency that’s a hallmark of the technology. Aguilar’s AG 500 uses a Class T output stage and a conventional linear
    power transformer.
  8. KJung

    KJung Supporting Member

    That has nothing to do with a switching power supply.... notice that they mention a conventional linear power transformer. The Ag site lists the amp as a 'type A. If it is a type D (it seems that it is), then the design is very similar to the iAmp and Epifani amp, that use traditional power supplies to get the low end 'wump', and class D amps (which do 'switch'... but that again has nothing to do with switching power supplies like those in the WW, AI and Stewart products) to allow the amps to run cooler.

    My guess is, the Ag500 will give your Stewart a run for its money in low end punch and volume (or maybe not... that Stewart wumps out a LOT of watts!). I really like the idea of a class D amp with a traditional power supply... kind of a 'best of both worlds' sort of thing.
  9. Quadzilla

    Quadzilla Supporting Member

    Thanks for the info K! The AG500 is surprisingly loud for 500 watts. Wow, sorry to take this thread off topic. I'll report back on my Stewart when I get it (by weeks end).
  10. KJung

    KJung Supporting Member

    +1 It's a great head. I didn't realize it was a class D amp... it's really warm sounding.

    Maybe some of the more EE type techies will weigh in here, since my knowledge is definitely at a 'layman's' level.
  11. paulraphael


    Apr 13, 2006
    If you heard me play, you'd stop reading what I write.
    traditional power supplies store quite a bit of energy. the amount of energy storage required to put out their average power rating means they can often put out two to four times their rating for brief transients. especially amps with massive power supplies. switch mode power supplies are light because their recharge rate lets them dispense with all the storage. This also means that their peak power is very close to their average (rated) power.

    i have a 1.2 ... it's very powerful. i'm mostly impressed with how authoritatively it controlls the speakers, and by how quick the transients are. it probably puts out 900 watts (bridged) into my 5.3 ohm cab. But to my ears, as good as it is, it doesn't sound as powerful as i'd expect from the power rating. If you blindfolded me and asked me to guess the rating, i'd probably guess 500 watts or so ... half the rating. This is based purely on its handling of big dynamics. It runs out of that last bit of headroom in a way that I wouldn't expect from a 900+ watt amp.

    My guess is that a similar quality amp rated at 600 watts, with a traditional, massive transformer and huge capacitors, would sound louder and more dynamic ... its peak output might be higher, maybe even by 6db or more.

    These are just impressions ... I haven't done a side by side comparison.

    Still, for my money, the 1.2 is an amazing amp. small, light, quiet, great sound quality, and plenty powerful, even if it's not the final word in loudness.
  12. KJung

    KJung Supporting Member

    +1 to this. My peers and I who own Walter Woods amps call them 'Walter Watts'. Walter Watts are equal to 'regular analog watts divided by two', which is pretty much what you seem to be hearing.

    That being said, a 7 pound amp (in the case of the Walter)that puts out the equivalent sound of a 600 watt traditional amp (even if it is rated at 1200 watts on paper) is none too shabby!

    I think again it has to do with the delivery of watts throughout the entire range of sound.... for some reason, amps like the Walter, the Acoustic Image, and the Stewarts, seem to just fall off in the lowest frequencies. They get plently loud, they just don' 'hit you in the chest'.

    Also, I've read posts from EE's on other threads that this is not necessarily a problem with switching power supplies in general, but rather with the executions of the designs in the market today.
  13. SteveC

    SteveC Moderator Staff Member

    Nov 12, 2004
    North Dakota
    I don't know about all the techno-talk, but my Eden 550 sounds better than my Acoustic Image Focus did. I'll live with the extra 15 pounds for the sweet tone I get.
  14. lowmid1

    lowmid1 Supporting Member

    Aug 16, 2002
    Baltimore, MD

    Switchmode power supplies are light because the size of the transformer required at the higher frequency is miniscule compared to the size of the transformer required at 60 hz. The energy storage is done with large electrolytic capacitors that weigh very little in comparison to the the actual transformer. I don't know about the Stewarts but the QSC PL2 series have large banks of storage capacitors on the front and back of the power supply. No lack of energy storage there!
  15. paulraphael


    Apr 13, 2006
    If you heard me play, you'd stop reading what I write.
    Are they large compared with the ones in a similarly powered traditional amp?

    That would seem strange ... big part of the reason for a switch mode power supply is to reduce the need for energy storage. A standard power supply recharges 120 times a second, so it needs stored energy for any demand that might be made between those cycles. Typical switch mode power supplies recharge a thousand times faster, greatly reducing the storage needs.

    The capacitors in my 80 watt/channel integrated amp on my stereo wouldn't even fit in the chasis of the Stewart 1.2 (but i don't know what's actually in there, because Stewart did a pretty good job of locking me out with all the little torx screws and warning labels and stickers that say "do not break this seal!"
  16. Supertanker

    Supertanker Watch the dog! He is trained to bite!

    Jun 23, 2005
    I have a Stewart World 600. It replaced a QSC 830. Five minutes after I turned the Stewart on and played through it the QSC was for sale on eBay.

    The Stewart sounds exponentially better than the QSC. It was literally like going from black and white to color.

    I think it has to do the switching speed. The QSC switched 120 times per second, the Stewart switches 120,000 times per second.

    The Stewart sounds fatter, louder, sweeter, faster, cleaner, clearer, smoother, and so on. There is absolutely no comparison...


    P.S. Not to mention the Stewart weighs 10 lbs vs 35 lbs for the QSC.
  17. lowmid1

    lowmid1 Supporting Member

    Aug 16, 2002
    Baltimore, MD
    There are 2 sets of caps, the larger ones on the front end which are similiar in size and quantity to a conventional amp and the smaller ones on the back end of the supply which are unlike any filter caps I have seen in other amps.

    From the manual:
    "Improved Power Supply-The PL2 power supply delivers 1200 watts more power than the original power light. The front end of the supply has 50% more energy storage while the back end storage has increasedby 236%. A regulated housekeeping supply has been added and switching losses have been reduced. These changes result in more efficient energy transfer to the output stage even during heavy loads and low AC line conditions."

    Bob Lee would be able to elaborate I would guess.
  18. lowmid1

    lowmid1 Supporting Member

    Aug 16, 2002
    Baltimore, MD
    I believe the QSC PL2 is switched at a much higher frequency than that. In my experience, the QSC and Stewart both sound good but the Stewart suffered when the line voltage was really low and the QSC didn't seem to be affected much?
  19. paulraphael


    Apr 13, 2006
    If you heard me play, you'd stop reading what I write.
    A switching power supply all that extra storage sounds like it could be the best of both worlds. If they design it well. How powerful is that thing and how much does it weigh
  20. lowmid1

    lowmid1 Supporting Member

    Aug 16, 2002
    Baltimore, MD
    About 22-23 pounds. PL236

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