Qsc Pld 4.5 Power Draw

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Power draw for PA system?

Thread starter ferrinbonn
Start date Mar 31, 2019

Hi all. My band has a couple of backyard parties coming up and I'm trying to figure out ahead of time if we're going to have power draw issues. We'll be running off of outlets (no generators involved) in the US, so 120V.

Here's a list of what we've got:

2 QSC KW 122 (1000 watts each)
5 Yamaha DBR 10 monitors (700 watts each)
Behringer x2222usb analog mixer
TC BQ500 bass amp (500 watts)
50 watt, 25 watt, and 20 watt tube guitar amps
2 keyboards (I don't know the brands, but they're midi controller types)
1 laptop
1 Behringer UMC audio interface

So on paper from the wattage ratings, we're looking at over 6000 watts, which adds up to over 50 amps at 120V. I can't imagine thought that all this stuff actually pulls that much power, but I don't know how to figure out how much it actually does pull.

For example, on the Yamaha site the DBR10s list "power consumption" as "60W(1/8 Power Consumption), 18W(Idle)". Does that mean that they only pull 60 watts under a typical use case instead of 700?

Any knowledge you can pass along would be greatly appreciated. I think best case we'd only be able to pull from 2 separate 15 amp circuits and I want to know ahead of time if we'd have issues with it. Thanks!

You seem to be confusing A/C input power wattage (current draw, which would be measured in amps, not watts) with amplifier audio output wattage. Find the power consumption specs for each component in watts, total them, divide by 120 or 115 to get total current draw in amperes. If the spec is in amperes, leave that out of the watts total and just add it to the final draw in amperes.

And for clarity, you want (if you need to) draw from two 15amp circuits, not just outlets (which may be on the same circuit). I'd be surprised if you're over 15 amps, total. For example, your QSC's draw 2.01 amps max on 120 VAC, at full power out. I doubt you run 'em that hot. Some of your gear draws in milliamps.

Last edited: Mar 31, 2019

As rusty said, you would be drawing about 2amps per qsc max and that would be with a good amount of clipping going on. At that point, your pa would be very loud and not sound very good. It could draw more than that but nothing coming from the speaker would be intelligible.

Speaker current draw is a little misleading because it isn't a constant draw at one level. Total system output wattage is useless and you need to look at peak current draw.

I can and have run something like two jbl srx835p and two srx828 as well as five qsc k12 and backline on a 20amp circuit. Ideally I'd like two but you get what you get sometimes.

Just the other day I ran a pair of rcf tt2a and one sub 9006 and two qsc pld 4.5 and all backline on a 20.

The thing to watch for is low Voltage. This creates more of an issue than anything else I've encountered. I've done a few backyard parties where the power was coming from a shed at the back of the yard or people ran extension cords 100+ feet. The power was crap, and the the extension cords were something like 16 gauge. You can guess how well that worked.

Most gear today is very efficient. In a perfect world you should only load about 80% of the circuit to leave some room for stronger surges.

My guess is with everything, you will be pulling about 7-8 amps max under moderate loads but following 1/8 power specs which includes light clipping, your speaker total spec would be right around 8-10amps and that's crushing them into limiting.

Those dbr claim to use 60 watts at 1/8 draw which is only half an amp.

You will be fine but as a backup be prepared to run a second line to a separate breaker if needed.

Last edited: Mar 31, 2019

bands in bars run the whole PA and all the band amps off one 20A wall socket all the time.

if you're rocking a "backyard party" then you'll be fine, the main issue will be overly long extension cable losses like @sants mentioned. extra-fat cables will help here.

the other issue will be lights; as long as you're using LEDs then that will be fine too but one old-school heavy&hot par light can draw as much current as the entire PA.

Those dbr claim to use 60 watts at 1/8 draw which is only half an amp.

Thanks for the great info. What is the 1/8 draw thing about? Is that some sort of industry standard way of measuring?

Thanks for the great info. What is the 1/8 draw thing about? Is that some sort of industry standard way of measuring?

It's power draw under light clipping conditions.

From qsc

"Current draw at 1/8 of full power is measured with pink noise and a sine wave as a signal. It approximates operating with music or voice with light clipping and repesents the amplifier's typical "clean" maximum level, without audible clipping. Use these figures for typical maximum level"

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