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uh-oh... techies, a little help please!

Discussion in 'Amps and Cabs [BG]' started by arcellus, Mar 6, 2004.


  1. arcellus

    arcellus

    Feb 28, 2004
    Portland, OR
    hey all, need some tech advice -
    i just bought an eden 210xlt (8ohm) and mackie m1200 power amp (1200w bridged @ 8ohm), both used, and am having a big problem... the sound is VERY quiet and distorted - fuzz in the low end, what small low end there is anyway. it sounds like something is being overdriven but i can't imagine what... i'm not an electrician but i did my best to trace the signal path - tested all speaker connections and solders with a circuit tester (is testing ohm load the right thing to do?) and everything seems fine.
    i'm using an aguilar obp924 preamp but have eleminated that as a possible problem.. could it be the cab's crossover/input section? maybe the amp output? i've tried all of the amp's input and output configs with the same reslut.. i THINK all of my cables are okay... haven't tried switching cabs yet to eliminate it or the amp as the problem (don't have any others...)
    ANY IDEAS???? please give me some input and tell me i didn't get ripped off with a blown piece of gear.... HELP! :confused:
     
  2. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Hi Arcellus, I'd try to take either the amp or the cab (or both) to your local music store. Try the amp with another cab, and the cab with another amp. You can probably isolate the problem that way.
     
  3. Are you using the right cable to connect the cab bridged? I don't know if the amp has speakons, but speakons have to be wired differently for bridged operation.

    You can check by running the amp stereo. If the sound is ok then, you need a rewired cable.
     
  4. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    getting warmer
    Is the 924 the outboard preamp? Does that have enough gain to push the Mackie to usable power? I thought that preamp was meant for use between the bass and another pre.

    If you have another amp available, try running the lineout from that into the Mackie and see if you get a different response.
     
  5. Like Joris wrote:
    Before you start repacking everything, check to see if everything is working properly by switching the amp back to stereo and playing through each side to see if that works. If that works then you probably have not connected the speaker cables properly for bridging. When you bridge the amp you have to connect to both hot or RED posts on the power amp. If you're using bannana, plug into both red binding posts. If you're speakons (as Joris wrote earlier) they have to be wired a special way when you bridge. Hope this helps and..............
     
  6. arcellus

    arcellus

    Feb 28, 2004
    Portland, OR
    i'm sure i've got the cables connected properly.. i'm using banana connections, and have tried bridged and both sides of stereo.

    i thought the db924 would put out a pretty hot signal.. plus it says in the mackie's literature that it can use almost any level signal. i could be wrong though and if i am it sounds like this may be the problem.

    i won't be able to get anything to a music store for at least a few days, which is why i'm trying to figure this out on my own.

    thanks for your help and i appreciate any more suggestions!
     
  7. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    Be sure to also check all your interconnect cables. when the signal side of a cable is going bad, it can sometimes do this. You might also check for any corrosion on any connections, and clean them all even if there is no visible corrosion.
     
  8. arcellus

    arcellus

    Feb 28, 2004
    Portland, OR
    i just used all of these cables last night with a different setup and they seem fine... what's a good way to test them (besides plugging in and listening)?

    i'm thinking it must be the preamp.. not enough usable signal?

    this is what i get for trying to save a little money :meh:
     
  9. arcellus

    arcellus

    Feb 28, 2004
    Portland, OR
    okay - just checked some more specs:
    max output for the db924 is 18db;
    min input for the poweramp to run full power into 4 ohms is 4db.

    so it's probably not the preamp.

    i'm getting volume, just not as much as i think i should and it's very distorted - an input blown?
     
  10. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    Well, wiggling cables usually reveals a bad one. But in this case, it's hard to say without being able to experiment with it myself.
     
  11. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    Check the battery in your pre-amp.
     
  12. arcellus

    arcellus

    Feb 28, 2004
    Portland, OR
    all new batteries
     
  13. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    getting warmer
    arcellus,

    the 924 provides 18db of boost to the signal which doesn't really say what the voltage at output is, while the Mackie is seeking 4dbu or 1.23 volts for full power.

    Assuming the output of a bass is in the millivolts range I'm not sure that the 924 is the right pre for the task. Again, I could very well be wrong on the math here.

    Is the signal LED blinking on the front of the power amp?
     
  14. arcellus

    arcellus

    Feb 28, 2004
    Portland, OR
    signal led is blinking, but not staying on solid as i think it should... would an underpowered signal cause that distortion?

    thanks all for the help... i'm new to the whole pre/poweramp/cab game so you're all much appreciated
     
  15. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    Underpowered signals would not cause a distortion. It would cause lack of volume. There is another problem at work here.
     
  16. arcellus

    arcellus

    Feb 28, 2004
    Portland, OR
    that's what i thought tmo...
    i know i should be taking this problem to a music store.. i really don't want to be "that guy" bringing all my gear in with a dumb look on my face... i'd rather do that here :D
     
  17. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    Okay, to rule out the preamp, plug your bass directly into the input on your mackie. It will be quiet, but it should work. If It does and it doesn't distort, it's the pre. If it still does, it could be wiring in the bass, or the mackie. Try a different speaker if you have one.
     
  18. arcellus

    arcellus

    Feb 28, 2004
    Portland, OR
    i've done that, tmo... same distortion, just not as loud. don't have a different speaker to try (just a combo with no external speaker outs or poweramp ins).... i'm gonna have to get this to a music store **sigh**
     
  19. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    well, it may be your output jack on the bass. I have had that happen a few times. I don't think it's the mackie, they are usually either on and good or fried if they are bad. But you would know if the speaker was blown, I suppose.
     
  20. arcellus

    arcellus

    Feb 28, 2004
    Portland, OR
    don't think it's the speaker... i get the same sound even at very low volume. don't think it's the output on the bass as i've used it with my other amp and it sounds fine. arggh!