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*HELP* My new rig has a big problem - Amp cuts out

Discussion in 'Amps and Cabs [BG]' started by kgantzer, Sep 5, 2005.


  1. kgantzer

    kgantzer

    Mar 6, 2004
    Ohio
    My new rig has a big problem: the power amp cuts out and resets itself intermittently and frequently, and usually when I play something dynamic (i.e. slap or really digging in, etc.). There is no way to gig with this rig as it is now.

    Here is my signal chain.

    1. Roscoe LG3005 or Pedulla PentaBuzz (both are active)
    2. BBE BMAX bass pre-amp (www.bbesound.com)
    3. Stewart World 2.1 power amp (www.stewartaudio.com)
    4. Accugroove El Whappo 4 Ohm cabinet (www.accugroove.com)

    I already had the BMax serviced for the overly hot gain - but problem persists.

    Any thoughts from those more experienced with rack/separates?

    PS - I have tried different cables between the pre-amp and the amp, and between the amp and the cabinet - no luck!

    PPS - my old Acoustic 370 head works great with the Accugroove; it is just kinda limited as far as sound variety.

    Thanks,
    Kurt
     
  2. BurningSkies

    BurningSkies CRAZY BALDHEAD

    Feb 20, 2005
    Seweracuse, NY
    Is it getting too hot? Do you have enough ventilation to keep yer power amp from suffocating?
     
  3. This sounds like a power amp overheating. Is the amp capable of supporting the load you are providing?
     
  4. kgantzer

    kgantzer

    Mar 6, 2004
    Ohio
    No - plenty of ventilation, almost imperceptible heat.

    The amp is a beast, and is rated as follows:

    FTC Power Rating <0.1% THD
    20Hz-20kHz
    both channels driven
    400W x 2 @ 8 Ohms
    650W x 2 @ 4 Ohms

    FTC Power Rating
    bridged mono
    1350W x 1 @ 8 Ohms
    2100W x 1 @ 4 Ohms
     
  5. I just read this on their site and I am wondering why there is a rating for 4ohm bridge mono and no rating for 2ohm/channel stereo. It would have to be able to perform down to 2 ohms stereo to be able to handle 4 ohms bridged.

    If you are bridging it try it in one of the channels in stereo and see if that helps. You may not get all the power from the amp but that would help eliminate the possibility that you are overworking the amp.
     
  6. kgantzer

    kgantzer

    Mar 6, 2004
    Ohio
    I have tried it, but the problem persists. The Owner's manual shows power output 900W x 2 at 2 Ohms per channel.
     
  7. Lonnybass

    Lonnybass Supporting Member

    Jul 19, 2000
    Minneapolis by way of Chicago
    Endorsing Artist: Pedulla Basses
    Are you plugging the Stewart into a Furman?

    Lonnybass
     
  8. kgantzer

    kgantzer

    Mar 6, 2004
    Ohio
    No Furman in the power chain. Do you think the SW2.1 is that sensitive?
     
  9. Lonnybass

    Lonnybass Supporting Member

    Jul 19, 2000
    Minneapolis by way of Chicago
    Endorsing Artist: Pedulla Basses
    Yes indeedy, the Stew can be a sensitive beast. If there isn't enough juice coming in, the amp will shut down if pushed. I found that out the hard way on a gig wh Have you by chance tried plugging it in to an outlet on a different circuit?

    Lonnybass
     
  10. Monomer

    Monomer

    Jul 22, 2005

    ground loop?



    try using compression on the Bmax, set up so it compress when the bass is slapped.
     
  11. 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 model has no fan, is that correct?

    Do you have everything plugged into an extension cord?
     
  12. csholtmeier

    csholtmeier

    Feb 8, 2004
    omaha, ne
    I had this same problem when I was running a Bmax through an RMX850 bridged into an Ampeg 6x10. This was at low to moderate volume levels. Happened when I played with a lot of dynamics (slapping, aggressive picking). It seemed to me like it was an overcurrent situation, like a resettable breaker was being tripped and cooling off and resetting.

    The Bmax has TONS of low end. Try cutting your lows significantly.

    I didn't care for the tone of the Bmax, so I returned it. Slid an RBI in and never had the same problem. Also got way more percieved volume out of the same rig.
     
  13. Lonnybass

    Lonnybass Supporting Member

    Jul 19, 2000
    Minneapolis by way of Chicago
    Endorsing Artist: Pedulla Basses
    The Stew 2.1 does have a fan.

    Lonnybass
     
  14. kgantzer

    kgantzer

    Mar 6, 2004
    Ohio
    The SW2.1 has a fan - possibly two fans, one for each side.

    No extension cord - both BBE and SW2.1 are plugged into one dual-plug outlet - so same circuit.
     
  15. boogiebass

    boogiebass

    Aug 16, 2000
    It does indeed sound like the Stew is shutting down. I gigged for several years with a 2.1 and it was perfect, even when pushed rather hard. Can you hear the fan when it's on? Might be that the fan is not working properly. I believe I'd have it checked out. Could also be that the pre is cutting out, I suppose. You might try bypassing the pre and just going into the Stew with another pre or a Sansamp or something and see if the problem persists. Good luck!
     
  16. kgantzer

    kgantzer

    Mar 6, 2004
    Ohio
    No question that the SW is cutting out. Big question is "why?"

    I will try my Sansamp.
     
  17. 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
    When you described the phenomena to the people at Stewart, what did they think it was?
     
  18. kgantzer

    kgantzer

    Mar 6, 2004
    Ohio
    I sent them an email a week ago. I am still waiting on a response. It is good advertising for QSC! :)
     
  19. 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
    Okay, but that still doesn't help you. :) Do you have a phone number for Stewart? Give their tech support a call.
     
  20. kgantzer

    kgantzer

    Mar 6, 2004
    Ohio
    Stewart said "yup, sounds like a problem. Send it in."

    So there you have it - for now.