hi,

Q: What should be the correct power transformer rating for 100watt 4 ohm amplifier? FORMULA.

Q: 2x18" 1000watt loudspeaker, what should be the correct power amplifier in order to drive those speakers. FORMULA.


thanks

 

http://forum.allaboutcircuits.com/showthread.php?t=3002

 

hi,

Q: What should be the correct power transformer rating for 100watt 4 ohm amplifier? FORMULA.

Q: 2x18" 1000watt loudspeaker, what should be the correct power amplifier in order to drive those speakers. FORMULA.


thanks

you can use OHM's LAW and POWER LAW.

 

Also use some common sense.
Nobody plays an amplifier at full blast all the time. If the amplifier has its volume control turned up so that the peaks are barely clipped then the average output power is 1/10th to 1/5th of the power at clipping.

You need to know the efficiency of the amplifier to be able to calculate how much more power is needed from the transformer to heat it.

There is no correct amplifier. A 20W amplifier, a 200W amplifier or a 2000W amplifier will power the two 1000W speakers very well. A 10W, 100W or 1000W amplifier will also work well. It depends on how loud you want it to play.

 

As audioguru mentioned, consider the efficiency.

up to 50% of your power rating will be lost in biasing if it is a class A amplifier.

 

As audioguru mentioned, consider the efficiency.

up to 50% of your power rating will be lost in biasing if it is a class A amplifier.

No.
A class-A amplifier wastes 500% of its output power at clipping.
A class-AB amplifier wastes 50% of its output power at clipping.

A class-A amplifier wastes 500% of its max output power when it is idle.
A class-AB amplifier wastes a small amount of power when it is idle.

 

No.
A class-A amplifier wastes 500% of its output power at clipping.
A class-AB amplifier wastes 50% of its output power at clipping.

A class-A amplifier wastes 500% of its max output power when it is idle.
A class-AB amplifier wastes a small amount of power when it is idle.

Are you sure?
A class A amplifier dissipating 100W at idle should ideally deliver 50W to the speaker at full volume, which is only 100% 'wastage'.

 

I use an old Southwest Technical class A headphone amp. It dissipates 45 watts a side for less than 2 watts out. They sound great, but are very inefficient.

 

Elliot Sound Products have a class-A amplifier project that dissipates 5 times as much power as its output power.

 

Elliot Sound Products have a class-A amplifier project that dissipates 5 times as much power as its output power.

500% seems a bit harsh:

http://sound.westhost.com/efficiency.htm#classa

 

Elliot Sound Products have a class-A amplifier project that dissipates 5 times as much power as its output power.

Could it be that valve amps are ridiculously inefficient? I've only been thinking of transistor types.