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output headroom meters TH section displays red

theatercarptheatercarp Posts: 5
edited June 2010 in PA General Discussion
What is the TH section of the output headroom meters telling me. These indicators are lit green very seldom. They seem to go right to red with very little input to the DRPA+. The five sections below the line on the meter rarely go above the "signal" section (first LED) sometime they will go into the 20 DB LD, but rarely if ever above that, yet the TH LED on the display is red almost constantly. My question is, what does the TH stand for, and what does it mean when it is lit red? Secondly what could be causing this. I am not sure but whatever is going on seems to be make my amp (CROWN MA 2400) go into protect mode. I am using the amp to push three EAW KF300 per side bi amped. The MA 2400 is running the being driven by the mid section of the crossover, and powering the 12" speaker or low end of the KF 300's. Is this an impedence issue? (too many speakers on the amp)

Thanks for your help.

Comments

  • GadgetGadget Posts: 4,915
    Total Headroom probably.. and what your seeing is probably the compressors or limiters as they (yellow) indicate above threshold and (Red) limiting/compression activity. Shut your comps and limiters down and see what happens. I suspect you have your threshold set too low and that is what you see on the meters.
    Gadget
  • theatercarptheatercarp Posts: 5
    Thanks Gadget, do you think this could be causing the amp to go into protect mode (shut down for a few seconds)?
  • GadgetGadget Posts: 4,915
    Ok, I have that amp and I have driven 4, 12" McCauley speakers (OAP T1202) with 4" voice coils and the amp would overheat badly.. I had to put a big ass box fan on it unless it was sitting in an air conditioned space and idling...I have since moved it to monitors and there isn't an issue there. There is a HUGE difference between the 2400 and 3600.. as the 3600 is a BEAST (I have those also) and they never even flinch no matter what the impedance the load is. They just honker down and deliver the current...

    Now, compression and limiting schemes can cause amp overloading. You may have noticed the pyramid amp health scheme on the MA2400... those are the indicators of the power supply health...the ODEP (output device emulation protection) and when the red led's start to dim the power supply is sagging... "are the red LED's dimming?" If so then the power supply is being hit to the point it's running out of gas...

    When you hit the amp with limiting and or compression (before the amp) you can increase the duty cycle of the amp and then the average power needed exceeds the available power. This can cause the amp to prematurely sag and "brown" out. Be careful what you do compressor wise (limiting also) because this can CAUSE amp overload. This amp isn't, as I said like the other MA series amps... the 3600 and 5000 are SERIOUS amps, the 2400 is not in the same class...I don't know why.

    Make sure the comps and limiters are off, make sure the filters (on the front of the amp) are clean, and that there isn't a buildup (inside the amp) of dust and grit... and that the amp rack is not running amps that reverse flow the air, and maybe provide some help for the 2400's air flow...(fans)

    That's all I can tell you without more info....please note the condition of the ODEP lights when next you post so we can determine if it's thermal or power related..

    These amps are also VERY power hungry, make sure the Edison isn't sagging below 110-115 volts,.

    Gadget
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