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What's this about Stewart Power Amps & Dirty Power??

Discussion in 'Amps and Cabs [BG]' started by jokerjkny, Apr 29, 2002.

  1. jokerjkny


    Jan 19, 2002
    NY / NJ / PHL
    I was at a shop recently, and while looking at a Stewart World 600, the salesman said that the Stu's were tonally great, they didnt deal with "dirty" power too well and that i should use a line conditioner. huh? has anyone had problems with their Stewarts in this regard??
  2. Whappo Grande

    Whappo Grande

    Feb 9, 2002
    Sunnyvale, CA.
    Engineer: AccuGroove Speakers & Amps
    No power amps are immune to bad power & should have power protection. The Stewart is like all other in this regards, no more, no less.

    I've had no problems with mine.

  3. jburtonca


    Nov 25, 2000
    Ottawa, Canada
    I have a Stewart World 1.2 and while it is a very good amp, it is very sensitive to low voltage conditions. Stewart amps are "class H" digital amps and don't have transformers like most other amps. If they don't get the proper voltage they won't operate. I found this out the hard way when I tried to use it in the bandshell at a local park. What you need is not a line conditioner, but a volyage regulator. You can go for a rack-mountable Furman AR-1215 for $460 at:


    Or the Tripp Lite LC 1200 for $95 at:


  4. Rock City

    Rock City

    Apr 8, 2001
    I have to disagree STRONGLY! Stewarts are NOT like all other power amps. A class A/B amp is far less problematic when it comes to line voltage issues. I have a Stewart 1.2, and in most venues it performs fine. However, there are some places where I just can't use it as I've had problems due to poor wiring. I can use any other tube or A/B solid state amp in these places without missing a beat though. I have friends who have had problems in these venues with Walter Woods and QSC Powerlights as well due to similar switching design.
    I DO agree however that these are good amps, and mine has had no problems otherwise.
  5. Whappo Grande

    Whappo Grande

    Feb 9, 2002
    Sunnyvale, CA.
    Engineer: AccuGroove Speakers & Amps
    Perhaps the reason I've never noticed problems is because regardless of what brand amp I use, I always use a line conditioner.

  6. Rodan

    Rodan Supporting Member

    Feb 4, 2002
    Hollywood, FL
    so which is it. line conditioner or voltage regulator? I was thinking about getting a Stewart or QSC PLX, but I'm not too excited about the prospect of having to buy another piece of gear just to make it function properly.
  7. 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
    I can't speak for the Stewart amp (although I'll say that it does have a power transformer), but QSC PowerLight and PLX amps are not susceptible to problems from "dirty" power. Most power amps, though, don't need power conditioning; they sort of bring their own—or should, anyway. ;)

    Also, to clarify a couple other points in this thread: class AB and class H amps (these designations have nothing to do with whether the amp has a conventional or switching power supply) are not inherently susceptible to AC problems. Class H is a high-efficiency variation on class AB; you really only see it on higher-power models because the power savings should be great enough to justify the extra circuitry.

    One advantage of a well-designed switching power supply is that it can compensate to some extent for AC voltage variations. For example, if the AC voltage sags 10%, the maximum power capability of the amp with the conventional supply will drop about 19%, while the switching-supply amp might drop only a couple percent.

    The disadvantage is that if the AC is really soft, the power supply might not start up. For example, 120V PowerLight and PLX amps need the AC to be at least about 90 to 93 volts in order to start up. Once they do, they're fine unless the AC drops into the low-to-mid 80's. But that low a voltage indicates a real problem with the AC line that at some point needs to be addressed.
  8. Chuck M

    Chuck M Supporting Member

    May 2, 2000
    San Antonio, Texas
    I've been using Stewart Power amps for several years and have not had any problems caused by "dirty" power. I do, however, use a power regulator on gigs where the supply voltage is suspect. I believe a power regulator is cheap insurance regardless of the type of equipment used. I would not want to loose one of my Demeter preamps dut to a voltage surge.

    I presently have an older PA-1000 and a 1.6 World. These amps sound wonderful for bass. I personally have not heard any power amps that sound as good to me.

    I think the salesman was just trying to sell you another piece of gear. You should have it but not just because of using a Stewart power amp.

  9. jokerjkny


    Jan 19, 2002
    NY / NJ / PHL
    for some more info!

    i recently purchased a Demeter VTBP-201s and Stewart World 600 to go along with my Bergantino HT112. unfortunately, i cant seem to nudge the demeter's volume past 9 o'clock without the tone farting out on the low B and E strings. my onboard EQ is flat, yet it still does this. the stewart is in bridged mode and up half way. it handles 300 watts @ 8ohms. honestly, it doesnt sound that loud at all. my EA iAMP350 sounds louder with more headroom.

    could this be a problem with the "dirty" power?
  10. chucko58


    Jan 17, 2002
    Silicon Valley, CA, USA
    I paid for all my gear myself. Well, me and MasterCard.
    I doubt the farting is an AC power problem. More likely it's just our old enemy, clipping.
  11. Chuck M

    Chuck M Supporting Member

    May 2, 2000
    San Antonio, Texas
    I'll bet it is the cabinet. Take your rig to a dealer and try another cabinet. I've used my Demeter with a Carver PM-300 and a 210XLT and it is very loud and clean. Your Stewart should have lots of power.

    One other thing to try is to turn the amp all the way up and turn the Demeter down some to control the volume. The Demeter preamps have pretty high output and may be overdriving the Stewart. I usually run my Demeters at only about 1/4 volume.

  12. jokerjkny


    Jan 19, 2002
    NY / NJ / PHL
    around 9 o'clock, right!!!!

    hallelujah, chuck! you just might have eased my heart.

    maybe my demeter's not that bad after all. even tho my 5 string has a bart pre onboard, i run it into the passive jack. and unfortunately have to leave it at 9 o'clock. my only problem with this is that, i feel like i'm not letting the demeter breathe out all of its luscious tone. but i guess things are ok, right?

    what tubes does it come with?dya think replacing one of the sovtek 12AX7LPS tubes with a 12AT7 would alleviate the hotness issue? i've got a few Svet's and a Mullard lying about. hmm....

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