Theoretical maximum watts from amp on 240 volts?

[blakey72]

So just thinking about this this afternoon. What is that maximum number of watts (roughly) an amp could put out on a standard 240 volt household plug? I've seen 1.5kW amps, could these run on standard power?

[sakabatou]

I'm no expert, but on a standard household 10A circuit, theoretically it could draw 2400W.

some appliances do (eg vaccuum cleaner)

[stereo coffee]

It is a strange question, as to correlate AC mains to amplifier power, you are forgetting that semiconductor devices are usually used 

to amplify and  DC power supplies derived with losses from AC mains are involved. If you study semiconductor devices they will

have an upper limit of DC voltage,  with most manufacturers working within safe limits of these devices. 

 

Efficiency of amplifier classes further complicates such correlation. Suggest you study some electronics books dedicated to amplifier

design to get a grasp on what amplifiers do.  Doug Selfs series of articles are a good place to start   http://douglas-self.com/ampins/ampins.htm

as well some articles on power supplies.  

 

 

 

[Ittaku]

Depending on the class of amplifier (A, B, AB, D and other rarer) there are practical limits on efficiency of power out versus power in. Most amplifiers are class AB (though subwoofer amps tend to be class D) and practical limits are about 70% for those meaning regular 10A 240V outlets which can draw up to 2400W power are likely to give a max of about 1600-1700W. My subwoofer has a class D amp of 1500W RMS which is about the most you can realistically get, and 5000W peak - the peak is basically stored energy from charging up capacitors and cannot be sustained.

For more info on power amplifier class types see:

https://en.wikipedia.org/wiki/Power_amplifier_classes

Edited April 6, 2018 by Ittaku

[blakey72]

2 hours ago, stereo coffee said:

It is a strange question, as to correlate AC mains to amplifier power, you are forgetting that semiconductor devices are usually used 

to amplify and  DC power supplies derived with losses from AC mains are involved. If you study semiconductor devices they will

have an upper limit of DC voltage,  with most manufacturers working within safe limits of these devices. 

 

Efficiency of amplifier classes further complicates such correlation. Suggest you study some electronics books dedicated to amplifier

design to get a grasp on what amplifiers do.  Doug Selfs series of articles are a good place to start   http://douglas-self.com/ampins/ampins.htm

as well some articles on power supplies.  

 

 

 

Yeah I realize it is a strange question. I really don't know enough about amplifiers but am very interested. So I'm guessing the class of amp makes a difference to how much power it draws?

[stereo coffee]

6 hours ago, blakey72 said:

Yeah I realize it is a strange question. I really don't know enough about amplifiers but am very interested. So I'm guessing the class of amp makes a difference to how much power it draws?

Yes, the semiconductor used in amplifying audio signal with class A biasing for instance is very inefficient,

drawing lots of continuous current and produces a lot of heat in the process. It is though the most linear of

all the classes. As we go down the list, other classes of bias start to partially engage the transistor. 

 http://www.learnabout-electronics.org/Amplifiers/amplifiers56.php   producing small non linearity

in the process, and Yes you are right - using less power. 

 

Amongst the most clever of these audio amplifier types are those that have a low powered Class A stage, only

calling upon a lower class stage to supply the current, which is then filled in by the class A  stage.

Invented by Harold Black in 1936  it is seen as feedforward error correction in Quads current dumping amplifiers.

http://quad-hifi.co.uk/our-story.php?id=23

 

Whilst the current dumping models achieve very low distortion there is further opportunity for

improvement with power supplies. Whilst a zener diode   https://en.wikipedia.org/wiki/Clarence_Zener  and a

resistor satisfying bias looks simple ( see last paragraph ) , it also creates small unneeded noise which has

opportunity for amplification . Instead if we turn to devices like the LM329   http://www.ti.com/lit/ds/symlink/lm329.pdf 

we can access up to 15ma of current with little, noise added.  

 

It boils down to to mainly measurements, but also listening.

 

If we move away from discussion of audio briefly the same efficiency problems occur with radio frequency amplifiers.

Class C for instance is almost always used in FM transmitters as it preserves just enough linearity to still be usable,

and provide needed amplification.  

 

The emphasis with audio amplifiers is to have extremely low distortion, and the ability to drive a load. Almost all power

amps are voltage drive devices rather than current driven.  A forum discussing everything related to amplifiers is here:   http://www.diyaudio.com/forums/amplifiers/  

 

Commercial amplifier manufacture achieves advancement when physics or mathematics gives up new exciting

explanation, that simultaneously  satisfies the accountants calculating the wages of the staff involved. 

As you can gather, it is rare moment indeed where everyone is happy - but occasionally it happens. 

 

 

 

 

 

Edited April 6, 2018 by stereo coffee