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plx input question.

Discussion in 'Amps and Cabs [BG]' started by inazone, Sep 28, 2004.


  1. inazone

    inazone

    Apr 20, 2003
    Colorado
    The input of the plx is high (3402) and I have a preamp with low output. Would a compressor (dbx) in between work to boost the signal? Just a thought.
     
  2. ADuck5150

    ADuck5150

    Jul 31, 2004
    NJ
    Just outta curiosity, what preamp is it?
     
  3. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    Are you near Denver?

    Lord Valve (aka Fat Willie) at NBS Electronics can adjust the input sensitivity on the PLX for you. Last time I heard it was around $50 for the modification.

    Not to fear, the mod is sanctioned by QSC and all it involves is replacing four resistors (two pairs).
     
  4. Finger Blister

    Finger Blister

    Jul 8, 2003
    Yep.
     
  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
    What preamp do you have, and how much voltage can it put out?
     
  6. inazone

    inazone

    Apr 20, 2003
    Colorado
    ampeg svp-cl and I dont know what the output is. I think I read somewhere that the output might be .775 volts wich would seem to match the crest amp but compared to other preamps it still has very low voulme.
    I didnt want to have the plx mod done (at least I dont think so) cos it does great in the pa as it is. I dont know if the mod will make the pa run too hot.
     
  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
    Is that 0.775 volt a maximum or nominal level?

    Maximum means that it can't go any higher without clipping, and nominal means it's the typical highest average output it will normally do, but it would have peaks hitting maybe 10 to 20 dB higher.

    You can use a Rolls ProMatch[?/URL] or a similar level boosting product to boost a low preamp output signal up to a pro level.

    The amp will run hotter if you push it harder to put out more power. A lot depends on the load and the levels you push the amp to.
     
  8. inazone

    inazone

    Apr 20, 2003
    Colorado
    Thanks! Do you think the gain knob on the compressor will work to give the preamp more output if I run the comp after the preamp?
     
  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
    I don't know for sure, but IIRC, every dbx compressor I've worked with has had some gain capability.
     
  10. notanaggie

    notanaggie Guest

    Sep 30, 2003
    From the other posts on the svp-cl it doesn't seem so much to have low output as low gain.

    Since it is tube, it should be able to put out several volts, but you might have to crank it.

    And, I think there is supposed to be a change or mod for them that adds gain. There have been several threads about that unit, one just recently.

    http://www.talkbass.com/forum/showthread.php?t=144990