calculating power loadsm uk/13amp plugs

Discussion:

(too old to reply)

lewdslewrate

2011-09-13 11:01:48 UTC

Hi...any help on this? We are calculating the power consumption of
our equipment. very often we are in venues with a domestic 13amp
supply only.
We have x8 La-24 power amplifiers (rebadged lab gruppen?) (x4 driving
FOH 4-way l-acoustics mtd 115a/SB/118 speakers & x4 running x4 mtd
115a monitors....sometimes a Camco DL1500 adds an extra 115B for kick
monitor)
Consumption for la-24 amp is given as 4kw for a 2x 1400 watt output.
Can/how can?.... this information be safely used in power amp case for
usual consumption calculations. We have been running x8 amps plus all
the other FOH gear off x3 13 amp wall sockets. This is extra to the
associated x-overs and other gear etc!

A lot of people are saying it's fine...but i am not so sure....it
seems to break the math rules i am working on regarding 13amp supply.
any guidance appreciated.

Arny Krueger

2011-09-13 11:56:23 UTC

Permalink

Post by lewdslewrate
Hi...any help on this? We are calculating the power consumption of
our equipment. very often we are in venues with a domestic 13amp
supply only.
We have x8 La-24 power amplifiers (rebadged lab gruppen?) (x4 driving
FOH 4-way l-acoustics mtd 115a/SB/118 speakers & x4 running x4 mtd
115a monitors....sometimes a Camco DL1500 adds an extra 115B for kick
monitor)
Consumption for la-24 amp is given as 4kw for a 2x 1400 watt output.
Can/how can?.... this information be safely used in power amp case for
usual consumption calculations. We have been running x8 amps plus all
the other FOH gear off x3 13 amp wall sockets. This is extra to the
associated x-overs and other gear etc!
A lot of people are saying it's fine...but i am not so sure....it
seems to break the math rules i am working on regarding 13amp supply.
any guidance appreciated.

Depending on what country you are in, the name plate current draw of
equipment is determined based on rules set up by some safety board. In the
US it is Underwriter's labs. They have their own standard for coming up
with the maximum specified current draw of each piece of equipment.

In the case of power amps, the maximum current draw specification is a true
worst-worst-case number, but is usually somewhat less than what the amp
would draw at maximum output with a sine wave into a resistor that
represented the lowest rated speaker load impedance. Obviously nobody but
you have the resources to determine the current draw of your equipment as
you use it since that depends on your equipment, how loudly you play it, and
how much clipping you tolerate.

Current and power measuring equipment is now cheap and readily available. In
the US there is an inexpensive little plug in device called a Kill-A-Watt
that gives accurate average numbers. It gives averaged readings and ignored
short term peaks, but it is probably fast enough to predict whether or not a
circuit breaker will trip and dump your show.

Joe Kotroczo

2011-09-13 12:33:26 UTC

Permalink

On 13/09/2011 12:01, lewdslewrate wrote:
(...)

Post by lewdslewrate
Consumption for la-24 amp is given as 4kw for a 2x 1400 watt output.
Can/how can?.... this information be safely used in power amp case for
usual consumption calculations. We have been running x8 amps plus all
the other FOH gear off x3 13 amp wall sockets. This is extra to the
associated x-overs and other gear etc!
A lot of people are saying it's fine...but i am not so sure....it
seems to break the math rules i am working on regarding 13amp supply.
any guidance appreciated.

You may want to to look up the term "crest factor".

If you drive a single LA-24 hard enough I'm sure you'll be able to knock
out a 13amp fuse. Sound like you're driving your amps fairly mildly if
you get away with having more than one per 13amp fuse.

The question that comes to mind is why do you need this much power
(11.200 Watts into 4 Ohms) anyway in venues that only have domestic power.

--
Illegitimi non carborundum

Phil Allison

2011-09-14 08:39:59 UTC

Permalink

"lewdslewrate"

** Wattage consumption is 100% irrelevant.

The only thing that matters is the RMS amp draw that occurs on music
programme.

Easily measured, but not always specified, it is NOT related to the power
output in any simple way.

Also, amps with active PFC draw way less RMS amps from the outlet.

Also, 3 "wall sockets" may or may not equate to three circuits.

You need to get a clue and some expert help with your rig.

Wot a noob.

.... Phil

lewdslewrate

2011-09-14 08:46:44 UTC

Permalink

Post by Phil Allison
"lewdslewrate"

Hi...any help on this? We are calculating the power consumption of
our equipment. very often we are in venues with a domestic 13amp
supply only.
We have x8 La-24 power amplifiers (rebadged lab gruppen?) (x4 driving
FOH 4-way l-acoustics mtd 115a/SB/118 speakers & x4 running x4 mtd
115a monitors....sometimes a Camco DL1500 adds an extra 115B for kick
monitor)
Consumption for la-24 amp is given as 4kw for a 2x 1400 watt output.
Can/how can?.... this information be safely used in power amp case for
usual consumption calculations. We have been running x8 amps plus all
the other FOH gear off x3 13 amp wall sockets. This is extra to the
associated x-overs and other gear etc!
A lot of people are saying it's fine...but i am not so sure....it
seems to break the math rules i am working on regarding 13amp supply.
any guidance appreciated.

** Wattage consumption is 100% irrelevant.
The only thing that matters is the RMS amp draw that occurs on music
programme.
Easily measured, but not always specified, it is NOT related to the power
output in any simple way.
Also, amps with active PFC draw way less RMS amps from the outlet.
Also, 3 "wall sockets" may or may not equate to three circuits.
You need to get a clue and some expert help with your rig.
Wot a noob.
.... Phil

You are right. We have engaged an electrian to talk to us and our
local venue.

The rig had a spell around various festivals (UK Folk). Locally it
gets in to 2 large converted church halls and occassional marquees.
More frequently now, part is used in dance events where x4 115a/
SB115's are used in corners with x2 SB118's sometimes.

These are typically/often Generic '5 rhythms/Gabriel Roth' events
where the dynamic range of the programme and consequent power draw is
wide, with a lot of quiet/moderate levels. But when it rocks..it
rocks.

The original concern was to find a rig that had power and quality at
'low' (relatively) volume but with headroom when events demanded more.
It is rare now for the full rig to be pushed hard in the 13amp venues
but it did and can happen.

Sometimes the only option is to find a number of wall
outlets.....points taken about the ring main capacity......and so far
no ground loops.

We will get some of these gadgets and get some measurements.....but
what i glean from replies is.....caution...in fact...maybe don't do it
in some cases.

oh...and whats a "noob". ?

Phil Allison

2011-09-14 09:16:03 UTC

Permalink

"lewdslewrate"

Post by Phil Allison
** Wattage consumption is 100% irrelevant.
The only thing that matters is the RMS amp draw that occurs on music
programme.
Easily measured, but not always specified, it is NOT related to the power
output in any simple way.
Also, amps with active PFC draw way less RMS amps from the outlet.
Also, 3 "wall sockets" may or may not equate to three circuits.
You need to get a clue and some expert help with your rig.
Wot a noob.

You are right. We have engaged an electrian to talk to us and our
local venue.

** ROTFLMAO.

Sparkies have NO FUCKING IDEA on this one.

Post by Phil Allison
oh...and whats a "noob". ?

** Please, that is too much for me.......

... Phil

Bob Howes

2011-09-14 10:25:44 UTC

Permalink

Working out the ACTUAL power consumption of an audio amplifier can be very
difficult--because your 1400 watt amp is rarely putting out 1400 watts.
What's it actually putting out? Well, it depends on a lot of things,
including the musical style. For example, some electronic music or heavily
compressed CDs played by a DJ will use a lot more of that 1400 watts than a
live band with instruments. Beyond that, you have to factor in the amp
design--a lot of modern amps use "clever" (or is it "cheating") circuits
that store up some energy for brief transients but the standard circuitry is
capable of a lot less.

Frankly, rather than guessing, my recommendation for most gigging bands is
to go to your local Maplins and buy their El Cheapo power metre to put in
circuit and see what you're drawing and how near the edge you are.

For benefit of non UK people, the situation with power there can be a bit
confusing for outsiders. What's commonly referred to as a "13 amp socket"
has a 13 amp (or less) fuse actually in the PLUG. This fuse tends to be a
slow blow device that can take over current conditions for brief periods
without blowing. However, said 13 amp socket is NOT limited to 13 amps.
Typically, they are on a ring main with a 32 amp capacity. Of course, this
is where it gets messy in a bar situation--you may have all 32 amps to play
with--or the pub kitchen may be on the same circuit. If you have the local
knowledge, you may be able to draw all 32 amps or the circuit may be near
the limit before you plug in any gear. A good, well designed bar stage will
have a dedicated 32 amp circuit split into a bunch of sockets for
bands...but how many are good and well designed?

Phil Allison

2011-09-14 10:41:49 UTC

Permalink

"Bob Howes"

Post by Bob Howes
Working out the ACTUAL power consumption of an audio amplifier can be very
difficult-

** Its irrelevant to the problem of circuit capacity.

Cos that depends of RMS amp draw ALONE !!!!!!!!!!!!!

Post by Bob Howes
Frankly, rather than guessing, my recommendation for most gigging bands is
to go to your local Maplins and buy their El Cheapo power metre to put in
circuit and see what you're drawing and how near the edge you are.

** Its TOTALLY irrelevant to the problem of circuit capacity.

Cos that depends of RMS amp draw ALONE !!!!!!!!!!!!!

Post by Bob Howes
For benefit of non UK people, the situation with power there can be a bit
confusing for outsiders. What's commonly referred to as a "13 amp socket"
has a 13 amp (or less) fuse actually in the PLUG. This fuse tends to be a
slow blow device that can take over current conditions for brief periods
without blowing. However, said 13 amp socket is NOT limited to 13 amps.
Typically, they are on a ring main with a 32 amp capacity. Of course,
this is where it gets messy in a bar situation--you may have all 32 amps
to play with--or the pub kitchen may be on the same circuit. If you have
the local knowledge, you may be able to draw all 32 amps or the circuit
may be near the limit before you plug in any gear. A good, well designed
bar stage will have a dedicated 32 amp circuit split into a bunch of
sockets for bands...but how many are good and well designed?

** A sparkie MIGHT be able to say what amp load is already on the same ring
mains circuit.

But he would have NO CLUE as to the RMS amp draw of a bunch of audio power
amps.

.... Phil

Bob Howes

2011-09-14 10:52:26 UTC

Permalink

Post by Phil Allison
"Bob Howes"

Post by Bob Howes
Working out the ACTUAL power consumption of an audio amplifier can be
very difficult-

** Its irrelevant to the problem of circuit capacity.
Cos that depends of RMS amp draw ALONE !!!!!!!!!!!!!

Post by Bob Howes
Frankly, rather than guessing, my recommendation for most gigging bands
is to go to your local Maplins and buy their El Cheapo power metre to put
in circuit and see what you're drawing and how near the edge you are.

** Its TOTALLY irrelevant to the problem of circuit capacity.
Cos that depends of RMS amp draw ALONE !!!!!!!!!!!!!

Post by Bob Howes
For benefit of non UK people, the situation with power there can be a bit
confusing for outsiders. What's commonly referred to as a "13 amp
socket" has a 13 amp (or less) fuse actually in the PLUG. This fuse
tends to be a slow blow device that can take over current conditions for
brief periods without blowing. However, said 13 amp socket is NOT
limited to 13 amps. Typically, they are on a ring main with a 32 amp
capacity. Of course, this is where it gets messy in a bar situation--you
may have all 32 amps to play with--or the pub kitchen may be on the same
circuit. If you have the local knowledge, you may be able to draw all 32
amps or the circuit may be near the limit before you plug in any gear. A
good, well designed bar stage will have a dedicated 32 amp circuit split
into a bunch of sockets for bands...but how many are good and well
designed?

** A sparkie MIGHT be able to say what amp load is already on the same
ring mains circuit.
But he would have NO CLUE as to the RMS amp draw of a bunch of audio
power amps.
.... Phil

And the only way to know the draw on your amp is to MEASURE it, hence my
suggestion of buying a cheap power meter. The rated RMS output of the amp
is, as you say, meaningless when trying to figure out the RMS draw.

Buy a meter and know what you're using (or trying to use).

Phil Allison

2011-09-14 11:12:25 UTC

Permalink

"Bob Howes is an IDIOT "

Post by Bob Howes

Post by Phil Allison
** A sparkie MIGHT be able to say what amp load is already on the same
ring mains circuit.
But he would have NO CLUE as to the RMS amp draw of a bunch of audio
power amps.

And the only way to know the draw on your amp is to MEASURE it, hence my
suggestion of buying a cheap power meter.

** FFS how many times do you have to be told you are WRONG !!!!!!!!!!

AC power circuits have an *** RMS amp draw ** limit - this IS what heats
cables and make fuses and breakers trip.

The power consumption figure is not in any simple way related to the RMS
amps draw and hence IRRELEVANT !!!!!!!!

.... Phil

Bob Howes

2011-09-14 11:45:24 UTC

Permalink

Post by Phil Allison
"Bob Howes is an IDIOT "

Post by Bob Howes

Post by Phil Allison
** A sparkie MIGHT be able to say what amp load is already on the same
ring mains circuit.
But he would have NO CLUE as to the RMS amp draw of a bunch of audio
power amps.

And the only way to know the draw on your amp is to MEASURE it, hence my
suggestion of buying a cheap power meter.

** FFS how many times do you have to be told you are WRONG !!!!!!!!!!
AC power circuits have an *** RMS amp draw ** limit - this IS what
heats cables and make fuses and breakers trip.
The power consumption figure is not in any simple way related to the RMS
amps draw and hence IRRELEVANT !!!!!!!!
.... Phil

Bob Howes is not an idiot. He has real world experience. Your method of
sitting in your workshop dealing in theories would mean that you'd
practically never hear live music in any pub because your theory will say
that it would be impossible to provide enough power. The information
provided in any amplifier spec is insufficient to decide what you can and
cannot do with the mains available.

However, even the original question shows that it IS possible to run a
typical band from a few 13 amp sockets (misnomer).

The ONLY way to know for sure what you need to draw is to MEASURE what you
do draw. The Maplin meter I mentioned is designed to do exactly that--and
an awful lot of UK gigging bands use them.

Call names all you want...in terms of real world experience, you are the one
lacking and just trying to show off your supposedly superior (but in this
case useless) knowledge).

Phil Allison

2011-09-14 12:41:44 UTC

Permalink

"Bob Hows is an UTTER IDIOT "

Post by Bob Howes

Post by Phil Allison

Post by Bob Howes
And the only way to know the draw on your amp is to MEASURE it, hence my
suggestion of buying a cheap power meter.

** FFS how many times do you have to be told you are WRONG !!!!!!!!!!
AC power circuits have an *** RMS amp draw ** limit - this IS what
heats cables and make fuses and breakers trip.
The power consumption figure is not in any simple way related to the RMS
amps draw and hence IRRELEVANT !!!!!!!!

Bob Howes is not an idiot.

** He is a fucking ostrich - cos it he totally ignoring the issue.

Post by Bob Howes
He has real world experience.

** ROTFL !!!

All the know nothings on the planet say that.

Post by Bob Howes
Your method of sitting in your workshop dealing in theories

** This fool has no idea how circuit breakers operate.

Funny how they all at have AMP ratings on them - not power ratings.

And those AMPs are all RMS amps too.

Post by Bob Howes
The information provided in any amplifier spec is insufficient to decide
what you can and cannot do with the mains available.

** Now the fool is belatedly parroting me.

Post by Bob Howes
However, even the original question shows that it IS possible to run a
typical band from a few 13 amp sockets (misnomer).

** The OP claims he has a circa 30kW PA system - not a band.

Post by Bob Howes
The ONLY way to know for sure what you need to draw is to MEASURE what you
do draw.

** But measure WHAT ????????????????

YOU BULLSHITTING NUT CASE

.... Phil