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Guide for Goobers--PA Basics and Glossary for Newbies

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  • #31
    No problem - I use my equipment all year round in cold and hot weather and leave it in the trailer when it is not being used and have done that for over 20 years now. Never an issue. But, I will not leave guitars out. Unlike electronic gear, they are made of wood with delicate finishes that are very sensitive to temp changes(crack!)

    It can get really wet from the trailer sweating on the inside


    True, but it helps to have a trailer with vents(not on the roof!) My new Car Mate has a nice ventilation system that keeps out the weather.

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    • #32
      Do it all the time in Canada with temperatures down to -40 Celcius and have never had an issue with anything. Just let things warm up for a bit before operation once I move them indoors and have never had a problem i could say was caused by storing in a trailer/van/etc.


      Edit: Also used to rehearse in a garage that was not heated in the winter unless we were rehearsing. Turned the heat on half hour before we went in there so we ourselves didnt freeze, but never had any problems with equipment.

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      • #33

        True, but it helps to have a trailer with vents(not on the roof!)

        Yes, vents should help some. The problem with sweating seems to be when snow and/or ice is piled on the roof and the sun hits the side of the trailer, warming the air in the trailer. The colder (maybe upwards of 50 degrees colder) snow & ice on the room temperature is fairly effectively transferred through the roof skin of the trailer, so the saturated vapour pressure is exceeded where the warm/moist air contacts the cold roof metal... moisture condenses on the roof and commonly (as I found), it basically rains inside the trailer, on a clear sunny winter day. I'd guess so-long as the vents could keep the inside temperature similar to the roof tin temperature or keep the inside below freezing on clear sunny days, that should diminish or eliminate the possibility for inside roof sweating. Parking the trailer in the shade, so the sun can't get to it on sunny winter days, seems to help too. Removing the snow and ice from the roof before the sun comes out seems to help too. I still tarp my stuff in the trailer... just in-case.

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        • #34
          I have an enclosed trailer, NE Ohio, and haven
          -----------------------------------------------------------------------------------------------.
          Hate is like taking poison, hoping the other guy gets sick.

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          • #35
            Condensation is only a problem when the air inside the trailer has enough humidity that the water condenses out as the temperature falls below the dew point (100% relative humidity).
            -------------------------------------------------------------------------------------------------------------------------------------------------------------------
            Former product development engineer: Genz Benz, a KMC Music/FMIC/JAM Industries Company, continuing factory level product support and service for Genz Benz

            Currently product development engineer: Mesa Boogie

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            • #36
              Newbies please disregard Dave's method of clipping the kick and snare channel he's a pro so don't try that on your system.

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              • #37
                More Gain Stucture info.


                1. Turn power to amps off.

                2. Use pink noise and set level into and out of the board so that the output just flickers the clip (or full scale digital) on the output meters.

                3. Do the same on the next piece noting that you may have to reduce the input gain to reduce the level (output gain on the drive device is not the issue). Continue doing this until you reach the amps.

                4. IF you have a DSP speaker processor, note that the input and output levels MAY be different as some have programmable level features that can cause this offset. Generally, if you have an option, something around +24dBu on the input and output is pretty close. There are also some that have a significantly lower operating level (ie. the BBE DS-48) and it is not adjustable (hardware limited) so in this event you will HAVE to then lower the level at the mixer to get down to avoid overloading the input. That's just the way it is, and you can't use a pad in this case because there is not adequate make-up gain and limited maximum output level (M.O.L.). In fact, if you have a unity-thru (ie. 1:1) device that has limited M.O.L. and no make-up gain provisions then that will be the limiting factor in the drive electronic's M.O.L. for headroom calculations.

                5. Turn power amp's sensitivity knobs to the point where the limit LED just begins to flash. TURN OFF THE PINK NOISE AND TURN DOWN THE CONSOLE... and NOW (this is the important part), decide how much headroom you will need to insure adequate limiter operation on your amps (I choose between 9dB and 12dB for the average user) and turn the sensitivity controls up by that amount. This works on all amps that have an input overload point equal to or greater than the lowest M.O.L. device in the drive electronics. I mention this because there are a few amps that have an input overload point of less than typical (+22 to +26dBu) which will cause the input to clip before the limit/clip detector inside the power amp circuitry.

                Generally, a good rule of thumb ends up that operating the power amp about -6dB below rated sensitivity is just about where you will end up and the result will be that the amp limits at +12dBu (give or take a few dB) with a limit point about (22dBu-12dBu=10dB) below the clipping point ofthe drive electronics. This means that you can limit ~10dB before clipping will occur at the speaker and this will be either from clipping the drive electronics or the input stage of the amp (before the limiting circuitry).

                There's really not need to go through all of this if you follow the rule of thumb, but it's good to understand why. When we design powered mixers (or musical instrument amps) with all the procesisng inside, we draw out a level and headroom diagram detailing each stage and pay close attention to operating margins at each step, taking into account available boost and cut within eq's, filters, dynamics, etc.

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