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Power amp power consumption question...
Old 30th January 2009
  #1
Lives for gear
 
soundawg's Avatar
 
๐ŸŽง 10 years
Power amp power consumption question...

When a power amp has no audio going through it, does it use no power? Does it draw its full amount from the wall all the time regardless? Or somewhere in the middle for some reason?

My uneducated guess is it might draw as much as the waveform asks it to by a factor of what the preamp is set at... which would mean next to nothing when no signal is present?



Can someone please explain/set me straight?

Regards,

Soundawg
Old 30th January 2009
  #2
Gear Maniac
 
stuntbutt's Avatar
 
๐ŸŽง 15 years
Power amps will always draw less at idle. How much less depends on the design of the amp.

For example. the Crown Macrotech 2400 draws 100w at idle and up to 1800w full-tilt. Average use would be around 1000w, or 8 amps at 120 volts.
Old 30th January 2009
  #3
Gear Nut
 
๐ŸŽง 15 years
I believe you're correct. If the amp is distributing its full potential, it draws much more power than if it is sitting idly by.

When I was younger & I ran sound for a band & we sometimes played in venues w/ no PA. I'd bring my own rig. I knew my systems limitations based on the power I was able to pull (how many circuits at how many amsp) from experience & a couple times at a certain venue, I was begged to turn the sound up just a smidge more (hitting about +3 on my boards output meters) - that's when the circuit would innevitably trip But only then. Therefore more input to the amps drew more pull from the power source - enough to pop the circuit.
Old 30th January 2009 | Show parent
  #4
Gear Nut
 
๐ŸŽง 15 years
Also, an amp draws a ton of power upon power-up, I believe its called the in-rush. Therefore, if power is at a question, power your amps up one @ a time & let them go through their powerup seqeunce before turning on the next one (about 5-10 seconds each).

I've seen people pop a circuit by turning on their power conditioners & having like 5-6 amps all powering up simultaneously.
Old 30th January 2009 | Show parent
  #5
ark
Lives for gear
 
๐ŸŽง 10 years
Also, some power amps draw as much or more power when they're running at about 1/3 capacity than they do at full capacity. They also get very hot.

The Federal Trade Commission caused a lot of trouble (probably by accident) because of this behavior. When they set advertising standards for consumer amplifiers, they wanted to be sure that an amplifier could deliver a realistic amount of power without overheating. So they required that in order to claim a particular power output, the amplifier had to be run at 1/3 power for an hour before testing.

What they did not realize was that for many amplifiers, running it at 1/3 power was actually a much more severe test than running it at full power, and many amplifiers would overheat at 1/3 power even though they would have run just fine at full power.

They finally changed the rule to say that an amplifier was allowed to overheat during this test, provided that it shut itself down safely and was not damanged.
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