Members Rbts Posted March 25, 2004 Members Share Posted March 25, 2004 High School was a long time ago, but Iremember that"amps = wattage / voltage".... so that a 100 watt light bulb will "draw" about .9 amps of current at 110 volts... right? In this same way, will a 500 "watt" amplifier then draw about 4.5amps? Or is this a whole different sort of watts or something? Asked another way... is there a way to determine how much current a stage full of equipment is going to draw, and to thereby make sure that one has sufficient juice available.. We are movinginto the outdoor season again, and this year's party looks to be alittle bigger than last year's party... Thank you to any who may have experienceor knowledge to lend. Link to comment Share on other sites More sharing options...
Members Old Steve Posted March 25, 2004 Members Share Posted March 25, 2004 I'm sure that there's a simple way to figure it out, but I know that from my experiences (aka past failures) that you also need to worry about sudden peaks in output shutting things down. So while everything may run just fine, when the whole band hits the same heavy chord at the same time the kick drum gets hammered and the lights suddenly come on for a cool visual effect, THAT's the exact moment when you trip the breakers. Link to comment Share on other sites More sharing options...
Members agedhorse Posted March 25, 2004 Members Share Posted March 25, 2004 Average watt input power = average watts output power plus watts consumed due to inefficiency (heat produced). This neglects additional reactive current (not real power) due to non-zero power factor of many amplifier's power supplies. Link to comment Share on other sites More sharing options...
Members Rbts Posted March 26, 2004 Author Members Share Posted March 26, 2004 All good comments, thanks.. agedhorse, the relative inefficiency seems to be the question mark in your comment... how much energy is lost in heat due to inefficiency? Is Pro audio gear generally closer to 40% efficient,... 60 % efficent?? any idea? Ilike what Steve B said, about adding up the fuse values... the rest of what you dsaid though I was not sure how totrnspose that over to 110 Volt current like here in the states? Thanks though everyone. Link to comment Share on other sites More sharing options...
Moderators MrKnobs Posted March 26, 2004 Moderators Share Posted March 26, 2004 Originally posted by Rbts Is Pro audio gear generally closer to 40% efficient,... 60 % efficent?? any idea? The Crown K series amps are about 85% efficient , which is one reason I like them so much. I don't even have to bring my PD to small club gigs anymore. Unless I bring lights, of course. Terry D. Link to comment Share on other sites More sharing options...
Members agedhorse Posted March 26, 2004 Members Share Posted March 26, 2004 Power amp efficiency (average) depends on the output topology. Class AB is typically about 45% efficient Class G/H is typically about 65% efficient Class D and Crown K series (a form of Class D) is about 85-90% efficienty Dynamic (sliding) class G/H (Sunfire, Bash) is also about 90% efficient. Link to comment Share on other sites More sharing options...
Members Rbts Posted March 29, 2004 Author Members Share Posted March 29, 2004 I am just so unsure of myself these days.. thank you for the info what is a PD? I understand the math that you spoke of, I just didn't know if the europower was different in other ways as well?? The circumstances that I am about to encounter is to stage some outdoor music on two 20 amp fuses. We did it last year no problems, but the stage will be bigger this year, with a bigger PA, and more back line.... so I am a little worried... The existing circuits are about 110 feet away from the stage... Additional circuits would be available, but they are more like 300 YARDS waway, and clear on the other side of the little lake... it would seem to be an awfully long wire run?? (costly, in wire, and possibly power loss?) Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted March 29, 2004 CMS Author Share Posted March 29, 2004 Originally posted by Rbts I am just so unsure of myself these days..thank you for the info what is a PD?I understand the math that you spoke of, I just didn't know if the europower was different in other ways as well??The circumstances that I am about to encounter is to stage some outdoor music on two 20 amp fuses.We did it last year no problems, but the stage will be bigger this year, with a bigger PA, and more back line.... so I am a little worried...The existing circuits are about 110 feet away from the stage...Additional circuits would be available, but they are more like 300 YARDS waway, and clear on the other side of the little lake... it would seem to be an awfully long wire run?? (costly, in wire, and possibly power loss?) PD = power distro, short for power distribution. A box or other means of providing multiple receptacles and protection close to the point of use. In other words, a box with lots of outlets and breakers, with a long heavy-gauge cable that runs to the venue's breaker panel. It's either plugged in (if you've never sinned in your lifetime), or you hotwire it by installing your own set of breakers into the panel. The math and power terms are pretty much the same around the world. A Watt is a Watt everywhere. To maximize the twin 20's you'll have, get the largest gauge of extension cords you can beg borrow or steal. Think 10AWG or larger. This will reduce voltage loss in the 110' run, lessening the cahnce of equipment drawing higher than normal current. Forget about going 900' to the other source. It would be cheaper to rent a genset and have it set up by a qualified electrician (the only way to do mobile gen power...be safe) than to buy the cable you'd need for that long a run. Link to comment Share on other sites More sharing options...
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