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Parallel Inputs?

Discussion in 'Amps and Cabs [BG]' started by Juniorkimbrough, Jun 23, 2005.


  1. Juniorkimbrough

    Juniorkimbrough

    Mar 22, 2005
    Mississippi / Memphis, TN
    Endorsing Artist: Lakland Basses
    Just got my new QSC RMX850 in and I am setting all the configuration switches.

    I've read the instructions several times but I'm not sure if I am understanding them right.

    I plan on just running one cabinet in bridged mono mode, and don't plan on using any other amps.

    do I need to turn the parallel inputs on or off? i'm thinking i need to turn it off into "stereo", is this correct?

    Thanks!
     
  2. Juniorkimbrough

    Juniorkimbrough

    Mar 22, 2005
    Mississippi / Memphis, TN
    Endorsing Artist: Lakland Basses
    anyone?
     
  3. pbd

    pbd Commercial User

    Jul 17, 2003
    Metro Detroit
    owner Procables N Sound
    You'll set your parallel switches 'OFF' and use channel one input only. If your manual is the same as mine it's on page 11 under the heading When to use it (or not).

    Technically it won't matter if your using parallel or stereo...just be sure your input is going into channel 1. I believe you will want to turn channel two "off" using the gain controls on the front if your in bridged mode.

    PBD
     
  4. Correct, parallel should not be set.

    There should be a bridge switch somewhere. The bridge switch ties the inputs together too, but it ALSO reverses the polarity of one so they're out of phase. The phase reversal is required to get bridged output thing to work.

    Parallel switch might get you parallel mono instead of bridged mono if the amp supports that, or it might just be for convenience, running a PA in mono, running both amp channels, a different amp channel to each speaker, from a single output of the board if you're running the board essentially in mono.

    Randy
     
  5. pbd

    pbd Commercial User

    Jul 17, 2003
    Metro Detroit
    owner Procables N Sound
    The parallel will allow you to run a mono signal into the amp using one input and use each channel output separately. The parallel will also allow you to "daisy chain" to other amps whether your in bridged or stereo mode.

    See diagram with the large arrow on page 11 of your manual Juniorkimbrough.

    Your bridged mode switches are just below the parallel/stereo. Aren't those fun to play with, the tiny switches....at least they won't get "bumped" accidentally. I had that happen to my subs once (FOH) and checked everything BUT the spring switch in the Carvin amp we use. I had a little help setting up.... ;) I never have a problem with the QSC's being changed.
     
  6. Juniorkimbrough

    Juniorkimbrough

    Mar 22, 2005
    Mississippi / Memphis, TN
    Endorsing Artist: Lakland Basses
    Thanks for the reassurance folks! :)

    I set the amp up and used it at band practice last night and something didn't seem quite right. It seemed like it wasn't putting out much juice....I could barely be heard over the guitars and it occassionally clipped, when it did this i saw the speakers really "jump" which didn't look like it was too good for them.

    Here's the specs on the gear I have.

    Previous rig.....

    -Peavey Nitrobass head (which when hooked up to both cabs runs probably 350-400 watts)
    -410T Eden Cab (8 ohm)
    -210 Peavey Cab (4 ohm)

    now i'm using....

    -Sansamp BADDI as preamp
    -QSC RMX850
    -410T Eden Cab ( 8 ohm)
    -running in bridged mode at 600 watts
    -410T will handle 540watts RMS


    at first I used the new rig but wasnt' loud enough, then we took a break and I hooked up the previous rig and it was plenty loud, with no clipping at all.

    What's going on here?

    Would just hooking up those 2 extra 10"s make that much of a difference even when it pushing let wattage?

    Thanks so much! This is really frustrating me right now.
     
  7. Are you using banana jacks? For bridged output you use the two red connectors, NOT red and black. Otherwise you're only getting the std stereo power from 1 amp channel.

    For anyone out there using 2 cabs, if you hooked up two cabs, one to each red/black banana connector, the cabs would be out of phase with each other, produce very little bass. And you'd only be getting the std stereo wattage to each cab, most of which would be wasted cancelling each other's sound out.

    The correct way is to use the 2 red posts to one speaker, and if you have a 2nd cab, then from first speaker to the next one.

    Randy
     
  8. 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
    The bridging switches (#6 and 7) on the RMX amp don't tie the inputs together, but instead take a feed from channel 1's output into channel 2.

    In bridged mono, putting the inputs in "stereo" (switches # 4 and 5) will reduce the chances of user error. That's because if you parallel the inputs and accidentally turn channel 2's gain control up, the input signal will partially cancel the feed from channel 1, which will reduce the signal coming out of channel 2's output.
     
  9. Juniorkimbrough

    Juniorkimbrough

    Mar 22, 2005
    Mississippi / Memphis, TN
    Endorsing Artist: Lakland Basses
    steve, I am using a banana > 1/4 speaker cable and I have the pos.(red) banana plugged into the pos.(red) post on the amp and the neg. banana plugged into the neg. (red) post on the amp.

    okay, nevermind I see what you are saying now......

    Bob Lee, you have a PM. :)