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I'm getting mixed answers to this question on other boards, so let me know what yall think. I need to buy a power generator to do an outdoor gig that will support the following rig:

Amp running @ 400watts x2, 8ohms
Amp running @ 125 watts x2, 8 ohms
IBM T30 laptop
BBE 362
Behringer Crossover

I don't know much about electrical output, but my common sense would say that I need something around the following:

900 watts/1300 surge watts for amp #1 (spikes + heat runoff)
250 watts/400 surge watts for amp #2 (spikes + heat runoff)
100-150 watts total for everything else

Which equals about a 1300 continuous watt generator with 1900 surge watt capasity.

Am I thinking correctly here?

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C Mc
KJ, FL

Determine watts needed, take all of your piece individually.
Get the amp rating multiply that by volts, the answer is minimum watts it will require. You don't say which power amps you are running - these will require the most. So i'll base it on a QSC RMX2450 which is rated 500 watts x2 into 8 ohms. It's current consumption (amps) is 10 amps. The volts is obviously 120 (unless you are overseas). So 10x120=1200 watts needed just for this amp. Now i'll approximate for the other amp. Using a QSC RMX850 for reference. This one uses 5 amps. So 5x120=600 watts needed. So for you 2 amps alone, you will need a generator capable of 1800 watts continuous.

The processors are probably only going to nee a maximum of 10-20 watts each. And not knowing laptop requirements, looking at a spec chart it look as though it needs about 72 watts.

I would get a minimum 2000 watt continuous & would probably push that a little higher for your amps when pushed harder can actually draw even more (ever blow a circuit at a show).

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The actual power you are concerned with is the current requirements for the line input for each amp. It should be on the amp. a guess would be about 5 amps. Thats about 500 watts. Without the specs I cant tell exactly but I would think a KW or 1200 watt generator would work..

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Make sure you know the differences between peak amperage and RMS amperage. Peak amperage is often much higher than RMS amperage. Most power generators will absolve high current drains for a very short amount of time so your concern should be whether you need to meet the RMS amperage, then you use that to figure out voltage.

For example if RMS amperage is 1 amp but the peak can be 2 amps, if that extra 1 amp is only for 10 micro seconds, that should not trigger the circuit breaker. If it holds for 500ms, it will most likely trigger the circuit breaker. It's the total energy consumption, not always straight voltage x amperage = power, although it's a good estimator power needs.

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Seize the day and SING!!!

And don't forget to buy a Honda, which is quiet enough to run a show, and not be heard..

You got that right They are a nice generator and I think regulated better too.....

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Bingo..

Honda is what we always use. Light wight and almost noise-free.

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I can neither confirm nor deny ever having or knowing anything about nothing.... mrscott

When you type something like 125 watts at 8 ohms, I assume you are talking about speakr output, which has nothing to do with your requirements..... Near the AC input of any UL approved electronic ( or electric) device is a plate or label that tells you either wattage or amperage requirements.. THIS is what you need. An example of the difference is the home karaoke machine Duet II. it has two 40 watt speakes at 8 ohms, but the AC INPUT wattage reuirement is 32 watts...

Amps x volts equal wattage requirement. add 25% for safety and you're good to go.

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"No Contests, No Divas, Just A Good Time!"

" Disc based and loving it..."

When you play out in a bar how many receptacles do you plug into?

I use one. The breaker never blows. Now it is either a 15 or 20 amp circuit. I'm guessing in a business it's 20. So how many watts???

How many amps is the question. 20....

even if you can get away with a 2500w generator why would you buy one that will just barely do the job?? for the money spent I would not buy anything under 4000w. they do not cost much more, and when you want to plug in a couple (or more) lights you will have plenty of power. I see it the same as buying amps, buy big or you end up wishing you had...my generator is a 6500w unit, but i bought that when i was auto racing to run my tools and welder at the track. its too loud for a karaoke show.

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the voices arent real, but they have some good ideas

Personally I would run the computer and most of the rack with a power inverter from 12 volt batts. At the very least I would run the computer with a cig lighter inverter..The honda would be used for amps and lighting. Watch the gas and dont let it drop the load all of a sudden this produces spikes which would destroy a laptop or most sensitive circuits.

This comes from experience with maritime power and radars.

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You are correct about single plugs, they provide 20A at 110-125V, which is about 2200 to 2500 watts. I don't have a rig that needs that much power, specially at nominal usage. The differences between the plug in power and generated power is the peak demand difference. For the plug in, you are getting your supply from larger power source, your local distribution center, that can sustain all your amperage you need up to 20A.

For the generated power, what you get is what is generated. If there is a steady high demand for amperage, you may not get it to sustain. Something to think about, headroom amps when choosing the unit.

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Seize the day and SING!!!

They can, but the common plugs in the U.S. are not rated for that. A 20A plug will actually have the neutral plug tine at a right angle to the hot. And a receptacle rated at 20A will have the matching thing, which looks like a sideways tee. So you can't plug those into the typical receptacle.

The most standard plugs are rated at is 15A, which is enough to run a typical karaoke setup. But I wouldn't crank my 4000W of amps on a single one of those....

But all he needs is 20 amps of power.

For his particular setup! At least what he listed.

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http://www.hayesequipment.com/honda/generators/honda_super_quiet_generators.htm

wow, the power goes up and the noise actually goes down slightly! However, I'd rather have the 2000w over the 3000w, because the weight almost triples for only a 50% power increase. someone said to go bigger or you will be sorry, but 46 pounds vs 134 pounds is something to think about. your back may be even sorrier. you could always buy 2 2kers and run them in parallel. save on weight and go up in power and versitality. 4kw for 92 pounds, you could carry one in each hand....

or, check these out. more power and a bit quieter for 2. although more weight, but still manageable at 70 pounds each.

http://www.hayesequipment.com/yamaha_generators/ef2400is.htm

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Ok lets see... Lets assume the voltage on the output transistors is 12 volts and the line voltage is 120 volts. This requires a step down transformer. A step down transformer converts high voltage low current to low voltage high current. The ratio is 10:1 T0 provide lets say 12volts at 10 amps requires 120 volts at 1 amp at the primary..

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This is a generally true statement about power generation. It is very difficult to maintain regulation at low power levels, which is wny most low-power generators are not serious candidates for running things like pro audio equipment.

I have a 4KW generator that I push a 2200W UPS with, which gives me good enough power for computers.

After researching several threads the recomondations are at least 4KW. A power conditioner is not capable of handling this type of power and your higher wattage units have better regulation. Be sure and use a ground rod clamped to the generator housing. There have been cases of severe shock.

If I were to do this on a regular basis I would use power inverters with deep cycle batteries.

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