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Thread: Calculating Power

  1. #1
    Member DJ Elevate's Avatar
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    Calculating Power

    Hey all it's been a while. So I was asked to provide what power I need and embarrassingly enough this is still something I still don't quite know how to answer.

    I'm going to invest in getting a Kill A Watt device to measure, but in the meantime, I'm looking at QSC's documentation and they mention "1/8th" power. On a KS212C, the gain knob goes up to +10, with 0 being right in the middle. When documentation says "1/8th power", does that mean 1/8th at the +10, or 1/8th when it's at 0. I assume 1/8th of +10? So if I run mine at 0, I can basically take whatever number is listed at 1/8th and double it twice (That would be 1/2 of full power)?

    So if a KS212C is listed at 3W at 1/8th power, does that mean it's 12W running it at half (I assume this is 0dB), theoretically?
    Last edited by DJ Elevate; 09-22-2021 at 07:06 PM.

  2. #2
    Quote Originally Posted by DJ Elevate View Post
    I'm going to invest in getting a Kill A Watt device to measure,
    It's not designed to do that.
    Use a multimeter instead.

    Too much power will destroy the Kill A Watt device.
    But the number of US Supreme Court judges was always 6.
    Then it was 5, then 6, then 7, then 9, then 10, then 7, and then 9.

  3. #3
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    Get one of these:

    https://smile.amazon.com/dp/B07P8M7N...NsaWNrPXRydWU=

    I need to power a setup off of a battery pack for the ceremony in an upcoming event. I wanted to properly size the pack, was surprised to find that an ETX10, ETX18, and a half a dozen LED pars drew a whopping 65 watts peak at a pretty decent volume.

  4. #4
    Quote Originally Posted by shoot summ View Post
    Good item.
    Like a Kill A Watt but with overload protection.
    【Overload Protection】Overload warning displayed on LCD, when the whole power exceeds the rated power 1650W of monitor, LCD will display "OVERLOAD" with booming noise to warn the user, and automatically disconnect the power.
    But the number of US Supreme Court judges was always 6.
    Then it was 5, then 6, then 7, then 9, then 10, then 7, and then 9.

  5. #5
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    Quote Originally Posted by DJ Elevate View Post
    I'm going to invest in getting a Kill A Watt device to measure, but in the meantime, I'm looking at QSC's documentation and they mention "1/8th" power. On a KS212C, the gain knob goes up to +10, with 0 being right in the middle. When documentation says "1/8th power", does that mean 1/8th at the +10, or 1/8th when it's at 0. I assume 1/8th of +10? So if I run mine at 0, I can basically take whatever number is listed at 1/8th and double it twice (That would be 1/2 of full power)?
    Nope. It's got nothing to do with the position of the gain knob, and those ratings and that kilowatt thing are useless in determining real world AC requirements for PA equipment. This gear draws power is a very peaky manner and neither the published ratings or the kilowatt take that into effect, but the circuit has to deliver it none the less. If you want to be able to use the system at full potnetial the best estimate is to use the advertised amplifier power rating for each box.
    Paul O'Brien
    Old Tech Guy
    www.Techott.com

  6. #6
    Member DJ Elevate's Avatar
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    What's the difference between the Kill A Watt, and the device that was linked? Just overload protection? I learned about the Kill A Watt from another DJ who uses it regularly. I've bought both now.

    How do you guys go about calculating power requirements when clients ask for it? I'm less worried about using to full potential (for now) and more concerned about understanding how to calculate the total amperage needed.

  7. #7
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    There is a lot of learning on the job with this stuff, operating a system on a generator is very imformative for example.
    Electrical circuits are spec'd for a continuous voltage and current which is how most home appliances and light fixtures operate, but a typical electrical circuit will deliver more than it's rated amperage for a short period of time, the circuit breaker or fuse protecting the circuit has to heat up before it will trip, so a single 15A circuit will power a lot more audio equipment than you may expect. For example a system consisting of a single powered sub, 2 tops, controller, and laptop will work fine on a single circuit. That might be 3000w of advertised amplifier power but that does not directly convert to AC electrical power due to the crest factor and duty cycle of music, the average continuous power is often much lower... perhaps only 1/8th of it. And you can never be sure your rig will be the only thing on a circuit in a venue... particularly in older buildings, so to be safe ask for 2 circuits for a system like this.
    Last edited by conanski; 09-23-2021 at 09:29 PM.
    Paul O'Brien
    Old Tech Guy
    www.Techott.com

  8. #8
    Quote Originally Posted by DJ Elevate View Post
    What's the difference between the Kill A Watt, and the device that was linked? Just overload protection?
    Yep.
    I've always used a Kill A Watt to determine how much it costs to run stuff like an extra refrigerator or leaving my computer on 24/7. Because that was what all the discount store chains (Here in the USA.) used to sell.

    Having overload protection is nice. It not only prevents your power consumption monitor from getting fried it probably helps prevent blowing fuses/breakers on your equipment like a resettable power strip.
    But the number of US Supreme Court judges was always 6.
    Then it was 5, then 6, then 7, then 9, then 10, then 7, and then 9.

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