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power amp problems

Discussion in 'Amps and Cabs [BG]' started by geoffzilla, Nov 5, 2001.


  1. geoffzilla

    geoffzilla

    Oct 30, 2001
    Nashville, TN
    Endorsing Artist: Aguilar Amplification
    I recently ran a sansamp bass driver directly to a power amp borrowed from the band's PA rig to see how it would work. I usually run through a Hartke 3500(350 watts@ 4 ohms). The Power amp, and I'm sorry I don't remember the exact specs, was something like 600 bridged at 4 ohms. Everything was connected properly, and I couldn't get enough volume to come close to the Hartke.
    My question then, is has anyone else tried running a SABDDI as the only pre? The maual states that this can be done, but do they overestimate the gain leaving the unit? I was really looking into this as an alternative to my current amp setup.
     
  2. It sounds like there was something wrong with the amp or with the Sansamp itself.. The setup is fine, bbut something else might be broken. Are you sure that the Sansamp is working? Does the amp work? If not, then it probably was a connection that was bad, or a bad cord. Double check a couple things, and see what happens.

    jtbp
     
  3. geoffzilla

    geoffzilla

    Oct 30, 2001
    Nashville, TN
    Endorsing Artist: Aguilar Amplification
    Jim,
    I just wanted to let you know that I got it to work the other night. It must have been a bad speaker cable. That was the only thing that was different. The amp was a QSC 650. The tone was disappointing. I run the sansamp through my hartke 3500 set flat and get a much clearer tone. I figured that the less crap in the signal path, the less muddiness I'd get. Oh well, I was just trying something new for giggles.
     
  4. PJR

    PJR

    Jun 20, 2001
    N.E. PA
    ......You will find that the sound most bass players are accustomed to hearing is far from being uncolored or flat !!!

    ...and when you ran from Bass > DI > P.A. amp....you found this out !!!

    -Peter
     
  5. 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
    Hey Geoff,

    Are you sure it was a QSC or a 650? It couldn't have been both.
     
  6. geoffzilla

    geoffzilla

    Oct 30, 2001
    Nashville, TN
    Endorsing Artist: Aguilar Amplification
    Jim, I'm not sure in the least about the model. I know it was a QSC and I think it was a "USA" followed by some numbers. I thought it was 650. It was a hefty unit too. 3 spaces. I don't want to cause any heartburn for you if you're associated with the company or something. It just lacked the sound that I had expected to hear.
     
  7. 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
    I'm not Jim but I'll answer you anyway.:p

    Maybe it was a USA 850? That's a model discontinued about six years ago and replaced by the USA 900.

    The specs on the USA 850 were 850 watts bridged mono into 8 ohms and 1100 watts into 4.

    You said the volume wasn't high enough, but you're comparing an amp made to take instrument-level signals with one made to take line-level. Where did you set the gain controls of the amp and the SansAmp?
     
  8. geoffzilla

    geoffzilla

    Oct 30, 2001
    Nashville, TN
    Endorsing Artist: Aguilar Amplification
    Sorry Bob ;)
    I run all the controls at "12 O'Clock" except blend (%100 wet) and the level is around 3 O'Clock. I think it was an 850( it definitely looks at least 6 years old). It was running bridged to a 4 ohm load. If I ran the preamp any hotter, it would clip. The power amp was set at probably 3 O'Clock
     
  9. 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
    It's okay. I've been called Bill a number of times, but that was the first time I'd been called Jim. ;)

    If you ran the preamp any hotter, which would clip--the amp or the preamp? If the amp clips, then yes, you're maxxed out on power, but that should be a lot louder than almost any instrument amp.

    If you want to try the power amp again, feel free to turn the amp up (use channel 1's gain control; turn channel 2 all the way down) as much as you need to. It only takes about 1 volt of signal to drive the amp to full power.
     
  10. geoffzilla

    geoffzilla

    Oct 30, 2001
    Nashville, TN
    Endorsing Artist: Aguilar Amplification
    I might give it another shot, but I really need to figure out why the sound isn't what I'm looking for. I guess it's the combnation of the pre with the hartke that does it for me. I must be underestimating the amount of coloring that head does, even set completely flat.
    Thanks for all of the help and advice. I definitely feel like I know more about what's going on anyways.
    oh yeah. the amp was clipping, not the pre.