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had a big problem with new rig at rehearsal last weekend. (pics)

Discussion in 'Amps and Cabs [BG]' started by biff malibu, Jul 16, 2008.


  1. here is my rack.


    sounded GREAT for about 15 minutes. with the volume knob at 10 o'clock, the mackie went into protect mode for about 20 seconds and came back again...and did this over and over. :mad:

    the top of the mackie was hot to the touch, the internal fan was running smoothly, so today i removed the blank slot under the furman and moved the tuner and RBI both up one slot off the top of the mackie and i now have a 4 inch metal desktop fan about 1/2 inch from the mackie's intake fan in the back of the rack.

    like so:

    movedrack.jpg

    rackfan.jpg

    should this solve the problem?
     
  2. That should help

    Does the Mackie have vent slots on top ?

    My main gigging rig is a B1500 in a rack with a bunch of other goodies. I have room above it, and a fan in back. I run it at 2.67 ohms regularly, and it barely gets warm.
     
  3. Dunno, man, I don't see any vents in the top of the Mackie that you would have blocked. I'd think it should have been ok as it was, but obviously, it wasn't. Have you tried it in the new config? If all your vents are clear, you should be okay. If not, there might be a problem with your amp. Sorry.
     
  4. it sucks air in through the back and shoots it out the front. no vents on top, but the top WAS very hot to the touch.
     
  5. Juniorkimbrough

    Juniorkimbrough

    Mar 22, 2005
    Mississippi / Memphis, TN
    Endorsing Artist: Lakland Basses
    think you overdriving the input on the mackie? I see you have the RBI cranked all the way up......I only have mine at 12 o'clock with a passive bass.
     
  6. i thought about that, but the mackie's overload light never came on, so i kind of ruled that out. :meh:
     
  7. Vanceman

    Vanceman

    Feb 14, 2007
    So. Cal.
    I'm going to go with Junior here. I've measured the output of my RBI at full gain and it exceeded 17 volts. Isn't the input sensitivity of the Mackie around .775 volts? I usually run the output of the RBI around 10 to 11 o'clock with a 500 watt amp, and it's plenty loud.
     
  8. Yeah, it looks to me like your power amp is turned way down. Max your power amp and turn down your RBI, and try it that way.
     
  9. maybe i'll take a look at that then. do you guys think it would have anything to do with some voltage/etc/whatever from it being run through a furman power thing?
     
  10. Naw, the Furman shouldn't bugger it at all.
     
  11. anderbass

    anderbass

    Dec 20, 2005
    Phoenix. Az.
    Also... it looks like your RBI's blend knob is set to 100% wet, you might find you wouldn't have to push your poweramp so hard (to cut through a loud band) if your blend knob setting was centered, and if you reduced the bass knob setting a bit and boosted your mid knob higher.
     
  12. :( but it sounds so good. :)

    those RBI settings are really things that would cause the poweramp to shut down though?
     
  13. Try it and see. What do you have to lose?
     
  14. SERPENT865

    SERPENT865

    Jan 1, 2007
    Wichita , KS
    +1
    I have never had my mackie ever turn off on thermals and I blast it all the time.
     
  15. bigfatbass

    bigfatbass Inactive

    Jun 30, 2003
    Upstate NY
    Endorsing Artist: Karl Hoyt Basses
    The RBI doesn't have an overload light. This is not a temperature issue, you are just overloading the input on your power amp. Turn the pre-amp down and your power amp up, 10 o'clock is part of your problem. Set the power amp to near wide open, more like 3 o'clock, then use the RBI to set your actual volume/spl. That will go a long way towards getting what you need out of that rig. If you want that full-blown distortion sound all the time, don't expect to get that out of an RBI. If you just want it to simulate a couple tubes gettin' nice and hot, then it is still the pre for you.

    The techie geeks can better explain why, but your power amp will actually be working less hard running it this way.
     
  16. xshawnxearthx

    xshawnxearthx

    Aug 23, 2004
    new jersey
    also, try facing the fan outward(pulling the hot air out of the amp). i could swear my 400+ and my 4 pro both have fans that are used to exhaust the heat.

    the "wet" knob shouldn't make a difference as far as over powering your amp. but having the volume cranked could be overdriving your input on the power amp.
     
  17. bongomania

    bongomania Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Having the blend knob to 100% wet does mean a significant mid scoop, which in turn means that you have to crank the output gain a lot higher to get the same perceived volume, which in turn contributes to overloading the input of the power amp.

    One other way to get more distortion out of the RBI is to slam its input with a boost or overdrive pedal. That kind/amount of boost will not harm the RBI or cause it to shut down (we're talking maybe 1 volt signal level when boosted, compared to the 17 volts of the maxed RBI output).
     
  18. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Overloading the input will cause distortion, but it won't make the chassis hot or cause the protect mode to kick in. That's the result of either insufficient air flow or too much current draw. If airflow is ruled out then you have to look at the load impedance, bad speaker cabling or improper bridging.
    It could. Power amps don't need 'conditioning' or voltage regulation, and devices incapable of delivering adequate current to the amp can cause them to overheat.
     
  19. i have been running it with the same speakon cable for bridge mode (which is what i use) in my room at home as i did at rehearsal with the band at big volume. wouldnt a problem like a bad bridging cable cause bad stuff to happen no matter what the volume and not just at high volume?
     
  20. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Yes.
     
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
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