Question about setting up a pre amp with a QSC power amp

Discussion in 'Amps and Cabs [BG]' started by Fawkes007, Jul 3, 2008.

  1. Fawkes007


    Sep 13, 2005
    SF Bay Area
    Hi everyone.

    So I am thinking of getting a stereo power amp so that I can drive both of my 4 ohm cabinets, 1 cab per channel. I don't want to run at 2 ohms.

    My question is, how do you hook up the pre amp so that you can run out of both channels? Do I need a cable going to each channel from the pre into the power amp?
  2. What power amp are you using?
  3. Fawkes007


    Sep 13, 2005
    SF Bay Area
    QSC GX5
  4. I have an RMX850, so I am not sure about that one but there should be a dip switch on the back that allows it. Check in the manual. If you put "QSC" in the title of your post Bob Lee will likely stop by and have a solution for ya'!

  5. bongomania

    bongomania Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Many power amps have a switch on them which allows both channels to be driven from only one input (e.g. from the mono output of a preamp).
  6. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio!

    Jul 3, 2001
    Chester, Connecticut
    Former Technical Communications Developer, QSC Audio
    You can use a Y cable.

    Or connect the preamp output to one channel's input. Use a second cable to connect the unused input jack on that channel to one of the input jacks on the othr channel.
  7. Fawkes007


    Sep 13, 2005
    SF Bay Area
    Thanks, Bob. I checked out the owner's manual on the site. Does it matter what kind of cable I use, ie shielded or unshielded?
  8. Wow deja day before yesterday:
  9. :D

    ... and that children is why you buy QSC...

  10. figuredbass

    figuredbass Supporting Member

    Jul 11, 2007
    NYC vicinity
    It should be shielded.
  11. brisonic


    Jan 1, 2006
    san diego
    qsc and perhaps other amps have the ability to bridge the inputs, so 1 input signal is sent to 2 independent channels.
  12. fish slapper

    fish slapper

    Nov 17, 2005
    Newberg, OR

    I just scored a GX5 :hyper: and am planning on using the two channels out to my two 4 ohm cabs. I'm interested in trying the unused input jack to the second channel to get the pre to both channels. Question: is it better to use the low Z input from the pre and use the high Z for the jump to channel 2 or vise versa?

    And for a complete noob when it comes to this stuff, is a "sheilded cable" something different that getting speaker cables?

  13. bongomania

    bongomania Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Speaker cables are unshielded. Instrument cables are shielded.
  14. bassman10096

    bassman10096 Supporting Member

    Jul 30, 2004
    You use an instrument cable between preamp and power amp, because, like the signal from your instrument, the preamp signal is not overly robust and is subject to interference from electrical and magnetic sources like radio signals. The shielding keeps the noise out of your signal. Once it is amplified to speaker-driving voltage levels by the power amp, it doesn't need protection from interference. So, your speaker cables are not shielded.