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Pre to Poweramp connection

Discussion in 'Amps and Cabs [BG]' started by monroe55, Apr 17, 2009.


  1. monroe55

    monroe55

    Mar 17, 2009
    Im sure you're exhausted from answering this question. I checked the searches and Im still confused. Balanced, Unbalanced, XLR, TRS, 1/4" conductor?????Blah,blah,blah..

    Im entering the whole preamp-poweramp gauntlet. I just got my new power amp QSC PLX1804. Afriend lent me an old preamp to use while I decide on one of my own. His is an old ART Parametric Tube EQ. He says it will work for now even though its not a straight up Bass Preamp. I just want to know how to connect the dam thing to the QSC. Its got an unbalanced 1/4" output or a balanced XLR output. Each channel on the QSC has an XLR or a 1/4" input.
    What do I do?
    One music store employee told me to connect the balanced XLR on the Preamp to channel one XLR on the QSC, then use a TRS cable to connect the 1/4" inputs on each channel on the QSC to "bridge" them. ??
    Another employee told me all I need is this adapter cable he showed me which has an 1-XLRfemale at one end and 2-XLR males at the other. Im supposed to connect the female end to the pre and the 2 male ends into each channel on the power amp?
    I feel that when Im done with all this power/preamp runaround I will be a certified engineer.:help:
     
  2. PSPookie

    PSPookie

    Aug 13, 2006
    Ocoee, TN
    I suggest reading the manual.
     
  3. XLR to XLR, would be best. Or, XLR to 1/4" TRS. The signal from your pre may be hotter on the XLR than the 1/4". QSCs tend to like a hot signal.

    You can use a short, 1/4 TRS, or TS jumper, on the PLX inputs, to run parallel mono, but that's not bridging. I'd use TRS, because I'm picky, but a difference may not be audible. MY QSC RMX has switches for parallel mono, your PLX may have switches as well. RTM.
     
  4. monroe55

    monroe55

    Mar 17, 2009
    Thanks Ulrich , that's what I was thought...XLR to XLR with a TRS jumper. Any idea why i was told to do it like the other guy told me.......

    "Another employee told me all I need is this adapter cable he showed me which has an 1-XLRfemale at one end and 2-XLR males at the other. Im supposed to connect the female end to the pre and the 2 male ends into each channel on the power amp?
    I feel that when Im done with all this power/preamp runaround I will be a certified engineer"?????????
     
  5. rpsands

    rpsands

    Jul 6, 2007
    Phoenix, AZ
    Connect the XLR to the XLR. Balanced, to channel one. The *04 series does not have "bridging" or anything.

    Sadly, it doesn't have parallel mono either from what I can see.

    If you only have one cab, all you do is:
    1) xlr out to xlr in, BALANCED -- unbalanced will lose volume and possibly make noise
    2) One speakon out to a cabinet

    If you have two cabinets, you need to get a Y cable like the one guy told you, to split the signal from one XLR out on the Art to both XLR in on the amp. Then run one speakon to each cabinet.

    You can also, if you don't need tons of power, just daisy chain two cabinets off of one power amp output.
     
  6. scottbass

    scottbass Bass lines like a big, funky giant

    Jul 13, 2004
    Southern MN
    You should definitely run an XLR from your preamp to Channel 1 of your QSC amp.

    rpsands is incorrect; you don't necessarily need to buy a "Y" cable.

    Either of the two options you listed will work and will have the same effect. You are just splitting the single-channel output of the preamp into two identical inputs for the two channels of your power amp. Electrically the 1/4" and XLR inputs on your power amp are connected in parallel, so it makes no difference if you create your "Y" by using an XLR 1-into-2 cable or by using a 1/4" TRS jumper from Channel 1 to Channel 2.

    I assume you are driving two speaker cabs, right? One will be connected to Channel 1 and the other will be connected to Channel 2? If so, using either of the above two methods will allow you to control each cab's volume independently using the power amp's two volume controls.

    If you're running only one cab, you can use only one channel of the power amp. In that case you would just connect the preamp to channel 1 and connect the channel 1 output to your single cab. Turn the channel 2 volume control all the way down. No Y cable or jumper cable necessary.

    That particular QSC power amp can not be bridged. (When you bridge, you are connecting both amps together into one high-power single channel. But your power amp can't do this.)
     
  7. monroe55

    monroe55

    Mar 17, 2009
    Thanks all. I know the amp cant be bridged.
    But what do you mean that " it doesnt have parallel mono"?
    I believe "Bridge" is just the term the guy used when referring to jumping the 2- 1/4" inputs on the amp. Is that whats called "Daisying".
    About that creating an external "Y" with a 1 in 2 cable.The adaptor cable the guy sold me (XLRF-2XLRM) looks awfully thin, like the thickness of an E string. Is that normal? Most cables Ive used involved with instruments,speakers, amps, etc. seem a lot thicker than this thing
     
  8. monroe55

    monroe55

    Mar 17, 2009
    BTW, Im using 2 cabs
     
  9. scottbass

    scottbass Bass lines like a big, funky giant

    Jul 13, 2004
    Southern MN
    Your XLR Y cable will be fine. The only reason other cables are thicker is to provide protection from bending, kinking, slicing through them with a falling cymbal, etc. Since your cable is very short and hanging off the back of your amp, there is no reason for the extra layers of protection.
     
  10. Y cable is fine.
    XLR to XLR, then TRS to TRS.
    XLR to TRS, then XLR to TRS.
    XLR to TRS, then XLR to XLR
    Whatevs, same thing.

    OT While it is fine to Y one output to two inputs, do not Y two outputs to one input.
     
  11. monroe55

    monroe55

    Mar 17, 2009
    Huh?

    Just kiddn. Thanks fo breakin it down for me brutha.;)
     
  12. Bob Lee (QSC)

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

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    From your description, the "adapter" cable seems to be just a Y cable, is that correct?

    If so, either method will work. Take your pick.
     
  13. Bob Lee (QSC)

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

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    Also, what Uli said.
     
  14. monroe55

    monroe55

    Mar 17, 2009
    I hooked it up......and it kicks Azzzzzzzz! This QSC1804 is gonna change my playin. This is what I been needin all these years. MORE CLEAN POWER!!!:bassist: Ive been suffering with a Hartke 7000a forever. What a joke. I only regret not trying a poweramp/pre setup sooner...or at least a better head. The gui****ists in my band will come to respect me now. Now, the search for the ultimate preamp begins.
    Aguilar? AmpegPro? Sansamp? Peavy? Demeter?:meh:
     
  15. Crabby

    Crabby

    Dec 22, 2004
    This setup works for me! The navigator is an amazing pre amp but I never knew how sweet it was until I got my PLX1804. Amazing lightweight rig!

    IMGP0563.

    IMGP0565.
     

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