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Trying to hookup Stereo out into mono

Discussion in 'Recording' started by Farmer, Dec 6, 2008.

  1. Farmer

    Farmer Guest

    We are reconfiguring our pa system at church. Equipment:
    Soundcraft Spirit E12 Series
    QSR rmx2450 amp
    Older pair of Bose 802 Speakers with controller.

    Trying to get both R/L main mix outs into one side of amp inputs. Making room to run monitor sig through other side of amp.

    Heres the problem. run up L main, sound comes out fine, but when you run up R main even with L, the sound disappears. Like getting canceled out. Heres how its hook up. Board: XLR on both L/R main mix out, connected to Bose Controller line 1 & 2. Bose controller line out 1 & 2, have y cable L/R to stereo (2- ts to 1 trs) going to amp channel one, then out to speakers.

    Any help would be great. Also any idea on a better way of doing it


  2. Codemonkey

    Codemonkey Well-Known Member


    You're going to a TRS input on the amp.
    This takes the L input, adds the Inverted R input, and that's the signal it carries (it's a balanced connection)
    So this is perfectly normal. What you want is another cable...

    If the only amp input is a single TRS, hmm...Nothing else on it?

    What's the Bose controller for? It's unrelated and won't make a difference but you could ditch it if it serves minimal purpose.

    Cheapo hack fix: Disconnect the cable connected to the controller's R line out.
  3. Farmer

    Farmer Guest

    Thanks for the help.
    Amp has three dif inputs. Barrier strip, xlr, trs.

    Controller was on there before I took over, but not really needed.
    The only reason Im trying to get the stereo sig going is for our CD's. Alot of them have separatet tracks for music and vocals. Have to use another channel. I want to get away from this.

  4. Codemonkey

    Codemonkey Well-Known Member

    Somehow you need to sum the signal to mono before it gets to the amp input.

    What makes you want to get away from the use of 2 channels, are they in high demand?
  5. Boswell

    Boswell Moderator Distinguished Member

    The Bose controller is the pre-equaliser for the speakers. The usual route would be to take the mixer output signal into the equaliser, from the equaliser output to the power amp input and then connect the power amp outputs to the speakers.

    If you only want a mono mix fed to both speakers, use your mixer to produce a single mono signal (L or R). Feed that as a balanced signal (XLR or TRS) to the Bose controller. Split the equaliser output to both the L and R inputs of the power amp. Each channel of the power amp feeds its own speaker, but they carry the same signal information in this case.
  6. GeckoMusic

    GeckoMusic Guest

    I agree with Code Monkey, The Y cable splits the balanced TRS signal to positive and negative halves, not left and right. So when you add these you will get zero.

    One solution:
    Connect L out of mixer XLR to channel 1 of power amp. Connect the power amp channel 1 to both speakers in series. Call this the main mix.

    Connect the Aux1 send from the mixer (TRS) to channel 2 of the power amp (TRS) connect that to your monitors in series. Call that the monitor mix.

    If you want to use the "Bose Controller" then it would go between the mixer and power amp. No Y cables.

    Amp QSR rmx2450 500 W 8 ohm, 750W at 4 ohms, 1200W at 2 ohms
    Bose 802 240/480W at 8 ohms
  7. pmolsonmus

    pmolsonmus Well-Known Member

    Spend the $100 you'll be using for cables/adapters/time and energy and find a used power amp to drive the monitors.

    I think you are asking for trouble when you're driving two sides of an amp at different levels. (monitors/mains) I've always been told that that is the safest route. Others may know more of the science than I do.

  8. Kapt.Krunch

    Kapt.Krunch Well-Known Member

    I've not heard that. That means that all those powered mixers that let you select may have an inherent flaw if you use it for mains and monitors? I've actually used 1/2 for lows, and 1/2 for mids-highs with no real problems....(other than not quite enough oomph from that particular amp for the lows....bass bin amp went kaput...had to do SOMETHING).

    May be an interesting discussion. If there IS a problem with that...I'd be curious to know why. :wink:

  9. Link555

    Link555 Well-Known Member

    Use only one side of the mixer output
    L= mono or R= mono,
    ...or am I missing something here?
  10. Farmer

    Farmer Guest

    These are all great suggestions and concerns.

    Link/ just trying to put stereo out of mixer into a mono setup using one side of the amp.

    For now Im just going with this setup until I absolutly need it. Right Mix out to right amp Balance to two bose 802 in series. Then left mix out to left amp to single monitor (for now).

  11. GeckoMusic

    GeckoMusic Guest

    The monitor mix has always been different that the house mix in every situation I have been in.

    I have found that using the the right main for the house mix, and left main for the monitor mix is very awkward. You end up using the pan pot to mix from monitor to house.

    I would recommend using the left main out for the house mix, and use a pre fader aux send for the monitor mix.

    For your CD and tape deck, use a 1/4 unbalacned Y (not a TRS to dual unbalannced 1/4" insert cable) And connect L and R to one side and the common side to the left input on the mixer. It uses the series output protection resistors of the CD player to make a summing input on the mixer.

  12. Link555

    Link555 Well-Known Member

    Do you mean Monitor mix, when you say Mono?

    Or do you mean a mono signal?

    I agree with Geko use your AUX sends to create your monitor mix. It can be in stereo if like you have 2 aux sends.

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