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Feedback full blast while Masters are down

Discussion in 'Sound, Music, and Intercom' started by Destrox, Sep 9, 2008.

  1. Destrox

    Destrox Member

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    Location:
    Memphis
    So the other day when the the Praise Team was practicing for Chapel at my school (had already set up mics and monitors and such). I started getting horrible feedback (this is a new system and we are using a Yamaha LS9-32). So of course I grabbed the Master and pulled it down and even turned it Off, but that didn't stop the feedback. The meter showing db was as high as it would go (surprised it didn't blow our new speakers) and I noticed the Reverb (I think it's called "Stereo Send" that it is being put through. Not too sure though as the board is pretty new and is my first digital board) was also at max. I didn't think much of Reverb and just remembered it later. I got the feedback to stop by pulling ALL the channels down. So I think it had something to do with the Reverb. Of course since singers and violin players are sound experts they all were convinced it had something to do with the monitors (but the feedback was over the mains). Another strange thing was right before it I noticed the EQ on vocals was weird (sounded suppressed), but the EQ was flat (I even turned off High Pass to make sure).

    So my question is, any ideas what caused this (I noticed that when it was set up, one of the monitors was close to a vocal mic, but I don't think that was the problem)? Do the Stereo Sends bypass the Master and go straight to speakers? Any way to prevent this in the future?
     
  2. avkid

    avkid Not a New User Fight Leukemia

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    Occupation:
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    If they are pre fade the master will not affect them.
    Stop using reverb.:eek:
    Using post fade sends should keep this from happening.
     
  3. Destrox

    Destrox Member

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    I have no clue what pre fade and post fade sends are. Any links that explain these?
     
  4. DaveySimps

    DaveySimps CBMod CB Mods Premium Member

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    Occupation:
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    It could be that your return for the reverb got bumped pretty high up causing it to feedback. Although not on the LS9, I have on a couple of occastion (with a PM5D and an M7CL), had a board feedback from what Yamaha tech support told me was a digital glitch. In short, the board got hung up briefly while processing something, and then over compensated causing feedback (in lay terms). Sounds like this could fit the bill in your situation; possibly. We just rebooted the board and everything was fine in our case.

    In general terms, prefade sends are aux sends whose levels do not change when the corresponding fader channel is adjusted. Post fade sends are just the opposite. The aux level (or send level) changes depending on what the corresponding channel fader does; ie. if you fade the channel all the way out the aux send will fade out as well (great for fading music effects and such), or the level increases when you increase the fader.

    ~Dave
     
  5. howlingwolf487

    howlingwolf487 Active Member

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    It sounds like maybe you had an internal feedback loop caused by you routing some/most/all of your reverb's output back into itself. Also, if you were running monitors from FOH, that could be a problem, as well.

    Make sure you know what does what before you go trying to run a show with that console. You should know what pre-fade and post-fade mean and how they should be used.

    Best of luck, read the manual, and keep on learning.
     
  6. philhaney

    philhaney CBMod CB Mods

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    Location:
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    A "send" takes the audio signal from an input module (a channel) and sends it to an auxillary bus. On an analog board these are labeled "Aux 1 Out" or "Aux 1 Send" on the back of the sound board. They are usually numbered because there is almost always more than one.

    Sends allow you to send the audio from any combination of channels to sound processing equipment not built into the sound board, like reverberation chambers, digital delays, flangers, etc.

    With "Pre" meaning before and "Post" meaning after, "pre fade" takes the sound from the input module (channel) before it gets to the fader. We use this at the church I attend to send audio to the monitors on stage. Running the fader up and down to adjust the mix in the house has no effect on the stage monitor level as this send is pre fader.

    "Post fade" takes the sound from the input module (channel) after it has passed through the fader. We use this to send an audio signal to the wireless Assisted Listening system (wireless headsets for people who are hard of hearing). Running the fader up and down affects the level going to the wireless headsets because this send is post fader. ;)
     
  7. Dillon

    Dillon Active Member

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    Location:
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    Three words: Routing, Routing, Routing.

    You need to do a bit of homework on how to assign outputs, busses and auxes on your console. Then you need to go through the whole setup and make sure each and every bus assignment is justified and correct.

    A quick note about pre/post -- no matter what an aux send is set to, pulling a main fader will NEVER kill the send to that aux. The main output is simply a sum of all the channels feeding your house system (if that's what you have it set up for, which is typical in most cases). Aux sends are typically used for routing audio to external units (ie, reverb) or other speaker zones (ie, monitor mixes).

    Read the manual. Draw some diagrams for how you want the audio flow (think water, pipes and valves in lieu of signal, wires and faders) and take some time to mess with the system when you have a chance.
     
  8. loki

    loki Member

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    I had a similar situartion on a recent tour, at two venues the Feedback started and kept going after i killed the masters and the Aux's, To this day i dont know how i managed that, the solution i used was to turn off the desk, drop the levels and turn it on again.

    Interesting way to wake up the audiance :p
     
  9. Destrox

    Destrox Member

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    Location:
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    So when the board was installed, the company never gave us a manual, just basic training. I was able to find it on the internet and will probably look through it this weekend. Thanks everyone for the help!
     

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