Power for a PA

[banjoboy]

Here's a weird question. My band has been asked to play a weekend wedding gig, which includes playing one night in a rather remote area without power. The folks who hired us want to know if a 1000 watt generator would suffice to run our PA. My system is comprised of a QSC Touchmix board, two QSC K10 speakers, and eight mics. I'm thinking probably need at least 2000 watts of power, but I really haven't a clue. Anybody ever been in this type of situation? Any idea of how much power is needed? Thanks for any input.

[wildpikr]

Have you checked the nameplates on the back of your equipment? It may tell you the power rating in watts [or maybe in VA which is the equivalent]. You could determine/estimate an overall power requirement from the sum of that data. If it only gives you the operating voltage and operating load [in amps] then it's simple to calculate the power in watts -- volts x amps = watts.

Hope this helps.

[Tim Griffin]

You can find the current draw specs for you products. its unlikely your equipment will draw any where near 1000 watts. You will need to add up current draw of everything connected to the generator. You want to be below that by 15-20%.

[kjbllc]

why don't you borrow a generator, and do a dress rehearsal, if it is important to make a good show.
all things considered, amps draw different power at different times, so better safe than sorry.

[Mandobart]

I went thru a detailed process to design and build an inverter power supply for my Carvin AG300, rated at 250 watts. The nameplate on the back says 100 VA, so the most it should draw is 0.9 A (100 VA/110 VAC). Here are a series of threads on this subject:

http://www.mandolincafe.com/forum/sh...PA-Power/page2

http://www.mandolincafe.com/forum/sh...0-Favor-to-Ask

http://www.mandolincafe.com/forum/sh...87#post1488487

http://www.acousticguitarforum.com/f.../t-181989.html

The short answer is a 200 W inverter is more than enough to power my amp rated at 250 W with an extension cabinet.

Your QSC's are rated at 1000 W. It's pretty well known that mfr's audio power ratings are somewhat suspect, see:

https://en.m.wikipedia.org/wiki/Audio_power

http://www.audioholics.com/audio-amp...-power-ratings

The QSC Spec Sheet says "AC Power Consumption 1/8 Power 100 VAC, 2.3 A • 120 VAC, 2.01 A • 230 VAC, 1.13 A"
If each speaker draws 2.3 A at 1/8 power, that's 4.6 A for the pair. 4.6 A X 120 VAC = 552 W (I used 120 VAC vs nominal 110 VAC to conservatively estimate the power draw higher). When I run my amp for a gig its no where near full power. My educated and experienced estimate is a 1000 W generator will work fine for your band unless you require maximum output from your sound system.

[Steve Ostrander]

One thing to think about: how long is the main power cord coming from the generator? Because if it's not long, you're going to be trying to play over the sound of that generator, and some of them can be pretty loud. I'd want to be at least 100 feet away.

Not a problem for a rock band, I guess, but maybe for an acoustic band. I've been in this situation before, where the generator was about 30 feet away, and it was kind of annoying. Luckily, it was a Honda and not very loud.

[almeriastrings]

In terms of current draw, you will be fine. However.... a bigger issue is how 'clean' the generator's output is. Digital boards in particular do not like dirty, unstable power supplies. I would try to test this in advance. You would not want your mixer re-booting itself in the middle of a show. I'd look at using a high quality UPS on the Touchmix to even out the (typically) somewhat erratic voltage and line noise from the generator.

Incidentally, those QSC specs for power output are accurate and cite RMS values. I've measured them myself. They're Class D amp modules in there. Total overkill on the HF side, of course, but the capability is there in the module.

[foldedpath]

I've been in that situation before (remote area for weddings), and I've handled it two ways -- either using a 12v marine battery and high quality inverter, like Mandobart's solution above, or just telling the client that we'll perform acoustically without amplification.

The acoustic solution can actually work pretty well if you don't have any wind to deal with. If the wedding party has an activity in a remote woodsy or beach location, it means they're looking for a "natural" ambiance anyway. Going acoustic can be a nice fit. Then you set up your main PA rig for the reception, dinner, or whatever else they're booking you for.

It's been a while since I've looked at it, but I think our duo's standard contract for weddings includes a clause that says the venue must supply properly grounded AC power for any area we're performing, and if it's not available we'll play without amplification. They sign off on that when we get our deposit, and then there are no misunderstandings. I do have that battery/inverter rig available, but it's a backup and used at our discretion, depending on how remote the area is (do I really want to haul it?) and how much we're being paid for the gig.

The one thing I absolutely would not do, is hook up my analog mixer and expensive K10 speakers to an unknown, untested generator. No way. There are liability issues beyond just potential equipment damage when using a generator outdoors, not to mention sound pollution issues. If it's not *my* generator or battery/inverter power source, it isn't going to be part of my rig.

Edit to ad: Another thing you'll run into when a 3rd party or the venue is supplying a gennie, is that inevitably, someone else like a videographer with lights or a food vendor will want to plug into it and draw down the voltage. Keep your power independent and under your control at events like this.

[Jonathan Reinhardt]

A test run would be essential. A 1000 watt generator is a very small generator. For anything. The plus side is that it may well be a Honda or Yamaha if it is that size. They have built in inverters. Line loss must be calculated. Too far away (several hundred feet) and you risk shutdown unexpectedly. And/Or damage. I agree with foldedpath.

[dhergert]

Our simple solution for this is buying some Roland Street Cubes and running on battery. Each Street Cube has two 6" speakers and can really pump the sound out pretty nicely. You can hook up and mix two mics on each cube. We're using two Street Cubes for our band plus a Roland Bass Cube for the bass. We use two very hot Sennheiser e935 mics for voices/instruments and two moderately hot Audix OM2 mics for instruments only. If you need more power, get one Street Cube for each mic.

All on AA battery power for up to ~18 hours.

We do have a full sound system for when we have easy access to AC power. I'm not saying the Street Cubes produce the greatest tone compared to what a full 4x500W system would produce, but being able to run on battery might be better than having to play over a generator while trying to produce sensitive acoustic music.

Also keep in mind that if you're running a generator, your audience background noise is going to also increase, since conversations will also have to be louder than the generator. So you'll be trying to play over the audience and the generator. Even with a Honda.

Just a thought anyway... Best of luck with your gig!

-- Don

[TonyP]

Been there done that, we lost a powered head to a generator that died. Won't do it again and I'd certainly not with the nice gear you've got. If you have to do it, I'd get a contract that covers the cost of replacement. Or just do it acoustic, but that's just me.

[pops1]

If you use extension cords that are long then they will drop voltage if they are not large enough. I like a 12 gauge cord and while they are readily out there most people don't buy them. You need to read the cord. A voltage drop from your cord makes your amp use more current and can damage it. Same reason construction equipment (drills, etc.) don't last as long on power cords that are too small. Sound travels very well outside and you don't need large equipment to carry quite a distance. Acoustic can work very well indeed, we have done that many times.

[mandroid]

a power conditioner in between the Generator and the amplifiers should help protect the amps ..

for this app, most are Rack Mount.

http://www.parts-express.com/search....er-conditioner

[Barry Wilson]

I had a genny die and blew a fuse. I didn't have any spares and had to run around during my break on a sunday. luckily I found some but took 3 stops to get one

I even use the little mobile cube with 4 inch speakers. I am surprised how much jam that little sucker has. I've used it as a fill pa when I am in the center of a market and point it behind me. everyone is always surprised the amount of clear sound it puts out. That said, I have done 3x4 hr gigs without charging my traynor travelmate 50. it is one of the best investments I have ever made

[almeriastrings]

Personally.... I would look for a good battery powered unit (like that Traynor) in this situation. I would not want to plug my own digital consoles or QSC's into a an unknown generator - not without cast iron guarantees of full replacement costs in case of damage. It only takes one really bad spike and your very nice stuff is toast.

[mandroid]

FWIW, Many Years ago, I saw a Willie Nelson show at the Old Wooden MacArthur court, U of Oregon

Willie brought his Own Industrial Diesel powered Generator and had a Long cable running inside the building

to Not rely on the House Power supply.

[Barry Wilson]

I rented the Traynor before I ever bought it. I had a $25 gift certificate and that got me the PA for I think 6 weeks use. I imagine for the day it would have been about $10? That is cheaper than blowing something up. And we are talking Canadian money so that is what $2 usd? haha