Stewart 2.1 / Furman compatability

Discussion in 'Amps and Cabs [BG]' started by Trucker, Oct 19, 2003.

  1. Trucker


    Oct 12, 2003
    Providence, RI
    I'm about to buy a used Stewart World 2.1. I just noticed that my Furman RP-8 says it can handle no more that 1800 watts. Does this mean that I can't plug the Stewart, which can put out 2100 watts, into it? Or if I do that I wouldn't be able to use the full power of the Stewart? Or are these the wrong numbers to be looking at?

    $500 is a good price for a used 2.1, right?

  2. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    yes great price
    the stew uses a 20 amp plug so you're gonna have to buy an adapter to plug it into a 15 amp plug
    look at it this way, more than likely you're never gonna use the full 2100 watts
    i plug mine into a 20 amp furman pl pro but that gets plugged into the wall which is invariably a 15 amp circut
    i never run into trouble cause i never run the amp flat out - and unless you're using four 4 ohm speakers or eight 8 ohm ones, neither will you
  3. Chace90

    Chace90 Supporting Member

    Feb 1, 2002
    Denver, CO
    Does this have to be done? I just bought a stewart 1.6 and my power conditioner is only 15 amps. The conditioner handles 1800 watts if that makes any difference. According to the stewart manual, the most power that the amp will draw is 5 amps at turn on, and around 450 watts max when it's running. Is the converter necessary?
  4. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    The Stewart 2.1 (and other similar amps that use switching power supplies) are odd animals. In a sense, the power supply is "transparent", it's almost as if the output stage were plugged directly into the AC outlet (the power supply will provide pretty much "infinite" juice to the output stage, in terms of the current required). The greatest current is probably at startup, if you just turn on the amp and it powers up immediately, there is a huge surge current when the transformer kicks in and the filter caps first charge up. This current could easily be 20 amps. If you have a fast blow fuse or breaker in your power strip, it's very likely that it might blow. The Stewart 2.1 tries to get around this by powering up "slowly", there's a built-in delay circuit in the power supply that doesn't turn the amp on for 30 seconds or so after you flip the switch, and the purpose is exactly to mitigate the surge current at startup. However, when you're playing loud and pumping at or near the full 2100 watts in bridged mode, the amp can still easily draw 10 or 15 amps during peaks and transients. The AC power cord can actually get quite hot under these conditions, and it would be a very good idea to have a power strip that can handle the high currents. On the other hand, very few of us will ever pump that much power consistently (unless you're doing outdoor gigs and driving huge subs or something). If you're only at half volume, you'll only be drawing half the current, so there's less of an issue with surges and transients. I myself have a Stewart 2.1, and I only use it as an extension amp, to drive subs for outdoor gigs. I don't plug it into my PL-8, I use a separate line cord and plug it into a separate socket if possible (or if that's not possible, I have a super-heavy-duty 3-way AC adapter that I got at Home Depot, it's intended for huge power tools and it handles 30 amps or so, so I plug the Stewart into one of the three sockets, and the rest of the gear into one of the other sockets). The other thought is, if you go to your local electronics store (or check the online parts supply places like Mouser or Allied), you can find a rack mountable power strip that will handle 30 amps. It may not have the pull-out lights and the other fancy bells and whistles, but it will handle the juice. I have something like that in my home studio, it's just a basic no-frills strip with 8 sockets that handles 30 amps. Something like that would probably be your best bet. Good luck, let us know what you find! :)
  5. Chuck M

    Chuck M Supporting Member

    May 2, 2000
    San Antonio, Texas
    "the stew uses a 20 amp plug so you're gonna have to buy an adapter to plug it into a 15 amp plug"

    I've owned several Stewart power amps and currently have a 2.1 World. They all have the standard plug.

  6. Mario Lewis

    Mario Lewis

    Jul 6, 2001
    Clinton, MD
    Adapter? I didn't need no stinkin' 'dapter!

    I had a Stew 2.1. Didn't need a special anything. Just plug it in and go.
  7. jdombrow

    jdombrow Supporting Member

    Jan 16, 2002
    Colorado Springs, CO
    Looking at the original question, I don't think there is any direct relationship between the 1800 watt rating of the Furman unit and the 2100 watt output rating of the Stewart.

    The 1800 watt rating of the Furman refers to how many watts it can handle on the AC power line. This is determined by multiplying the AC volts times the current draw in amps:

    120 volts x 15 amps = 1800 watts.

  8. 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
    That's not quite true. Switch-mode supplies and conventional supplies alike use capacitive reservoirs to smooth out the current demand from the AC mains. This energy storage is necessary at the very least because the audio power demands are not synchronous with the AC line, but it is wise to have enough additional storage to provide short-term peaks without having to draw it immediately from the AC mains.

    Switch-mode supplies tend to have lower source impedances than conventional supplies do, so the rail voltages tend to not drop as much under heavy current demand, but there are definite limits to how much current a particular power supply, whether switching or conventional, can safely provide.
  9. You should be fine with your 15 amp Furman with the 2.1.

    Worry Not!