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Amp Power Usage

Steve Keele

Steve Keele

Dec 4, 2007
22
33
www.flashbackbrothers.com
#1
Long time looker, first time poster.
I was doing a small corporate gig yesterday with my classic rodk band (guitar, keys, electronic drums, lead vocal and me, bass) at a park pavilion. We used the power from a few outlets at the pavilion. Half way through the 2nd song my Markbass 121p amp died. That never happened before. The keyboard player and I tried a different cords and finally a different outlet before we get it working. I was back in business. Unfortunately, it was in the same outlet as his keyboard and it kept powering off. We made it through the gig but it got me thinking about power usage.
The question is, is there any way to tell how much power an amp uses? I'm thinking of getting one that may use less power as a back up, if that is even possible. Any ideas are useful.
 
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#6
A3FE8866-9C75-43D6-B971-D8F66AA28246.jpeg
 
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#7
There are 2 different aspects to an amp's power demand:

1. Average power consumption (or current draw) which is used for calculating the heating effect and average voltage drop on a power circuit. This is a fairly long term event.

2. Dynamic power consumption (or current draw) which is used for calculating actual voltage drop on a power circuit. This is a fairly short term event.

Dynamic current draw is the instantaneous current draw of the power amplifier's circuit with whatever averaging effects that the power supply supports.

The dynamic current draw can cause short term voltage drop events that can trigger an amp's protective circuitry and shut the amp down. This voltage drop is usually due to excessively long power branch circuits, those that do not have adequate wire size for its length.

There are NEC codes that govern AC supply performance, but it's not uncommon for these to be either ignored or for mistakes to be made.
 
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#8
Steve Keele said:
I was doing a small corporate gig
Click to expand...

Was it in a convention hall?
Where maybe the hall is used for trade shows with many booths?
The walls and floors lined with many outlets, but they are twist type and require a supplied adapter to use the power.

I run across these quite a bit and each little circuit is limited to 7A or less, depends on the hall. It's not a standard 15A circuit. You have to pay the hall more if you want more power. The power breakout box will actually have a little sticker with the Amps it can provide.

Imagine all the booths where some are using a lot of power they use to just split up the bill, but now they can charge the big power users directly and the low power users can better afford a booth. It's much cheaper than trying to meter each booth.

It's best to put your power requirement in your band contracts so the halls and clients know well ahead of time. They should look when booking you. These days it often isn't done because class-D and LED lights barely use the power of older tech class-ab, tube, and incandescent lights.

It just takes a lot less power to run a band these days. It is pure and simple progress of technology.
 
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#10
One thing I ran into in a park type situation a while back was we kept tripping the breaker on the outlet but weren't drawing THAT much power.. Fortunately some guy who knew a lot more than I about electricity came along and told us we were using too light a gauge extension cord to run from the stage area to the only power source about 50 feet away. Something about drawing too much power over a too thin cable increasing hte load on the source... I showed up the next time with a 10 gauge cord that was almost twice as thick as the one we had been using and we never tripped the breaker again...
 
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#12
RyanOh said:
I've used a Kill A Watt plug to check power usage for all sorts of things. There are $20-25. Good to know what uses power, and even when something is "turned off".

For SS amps, crank it up and play low notes. Seems to be the biggest draw. Never tested a tube amp with it.

View attachment 3538311
Click to expand...

+1 on a simple watt meter like this!

Some of the more expensive watt meters have data logging now with timestamps.
You can see what lead up to a power incident.
More expensive ones also have bluetooth.
Some of the internet of things controlled outlets also have built in watt meters where the log usage into apps. These outlet adapters are cheaper than standalone watt meters but often need a hub. I have one that runs wifi and has a REST api for logging.

Every so called "power conditioner" should have these built in with data logging so they could show when they actually did anything. I don't understand why the power conditioner market resists actual data logging. My only guess is that it would show they actually hardly do anything useful.
 
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#14
More often than not, when I have power problems it’s because the “Dedicated Circiuts” that are for the band are actually shared with other devices that you don’t know about. Coffee makers, coolers, Pop Corn popper, etc in an alcove or something. These are high draw items that don’t run continuously, but seem to pop on at the worst time. The big problem with this is you have no idea these loads are there or how much they are effecting the circuit until it’s a problem. All the metering you want to put on your gear will never see these loads.

Outdoors is always a crap shoot. Long runs, and undersized wire are the usual suspects.

Another common issue is Neutral / Phase reversal and lack of grounding in “house” venue wiring.

Most of the time if we play outdoors we just automatically provide our own power, this has been great for us. Small stages (2- 12” Hi Pack, 2 subs, mixer, Backline for 2 guitar, bass, 2 keys) is easily covered with a little EU2000 Honda generator. Big stages with 2 hangs of line array, subs, FOH, Backline, and LED Lights we cover with a Honda EU7000is Usually.

We have even provided our own power on some indoor jobs where power was very shoddy or suspect.

Most gear is much more efficient than people realize. We still run minimum 12ga cables for
everything just to eliminate voltage drop issues during high current demand.

While all of these “Power Conditioners” and Protection systems look pretty. I’ve found most to be basically useless overpriced power strips. So I just don’t even bother with them. I do have metering on my main power distro though for load balancing across phases as needed.

YMMV
 
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#16
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#17
Steve Keele said:
Long time looker, first time poster.
I was doing a small corporate gig yesterday with my classic rodk band (guitar, keys, electronic drums, lead vocal and me, bass) at a park pavilion. We used the power from a few outlets at the pavilion. Half way through the 2nd song my Markbass 121p amp died. That never happened before. The keyboard player and I tried a different cords and finally a different outlet before we get it working. I was back in business. Unfortunately, it was in the same outlet as his keyboard and it kept powering off. We made it through the gig but it got me thinking about power usage.
The question is, is there any way to tell how much power an amp uses? I'm thinking of getting one that may use less power as a back up, if that is even possible. Any ideas are useful.
Click to expand...


This is a fairly common problem at locations where the wiring is not adequate for music performance. My brother had the exact same problem a few weeks ago. He brought out a nice PA for a gazebo gig in the town square that was sponsored by the city. His mixer and power amps would not even turn on, so he wound up doing the gig through an ancient powered mixer that worked on low voltage.

Since your amp wouldn't even power up, it wasn't the primary cause of the problem. Lights tend to draw constant current which can pull the voltage way down. If the voltage gets low enough, digital equipment will begin to malfunction, and equipment with protection circuitry will go into protect mode or refuse to turn on at all.

FYI the label on the back of your 121p should say 600W. I believe this is the maximum power the amp is expected to pull from the AC source.

My brother's solution was to buy a Honda generator. Hopefully he bought a big one because he runs a huge amplifier on his EAW SB850 subs.
 

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