Power output estimation of an Amplifier

[Efthimios]

The power of amplifiers is given in relation to the impedance of the
speakers ( 200W @ 8 ohms).

Since I want to bye an amplifier and connected to a coil with grater
impendence I will need the following info:

Does any of you know how to estimate the power output for grater
impendence of a commercial amplifier.

Is the relation between Ohms and Watts linear so I can extrapolate to
the required impendence from the data given from the manufacturers?

Brgds

Efthimios

 

[John Popelish]

The power of amplifiers is given in relation to the impedance of the
speakers ( 200W @ 8 ohms).

Since I want to bye an amplifier and connected to a coil with grater
impendence I will need the following info:

Does any of you know how to estimate the power output for grater
impendence of a commercial amplifier.

Is the relation between Ohms and Watts linear so I can extrapolate to
the required impendence from the data given from the manufacturers?

The first order (simple approximation) rule is that if you
double the load resistance, the power falls by half, or that
the output power is inverse to the load resistance. In
reality, if you buy an amplifier rated at 200 watts into an
8 ohm load and you use it on a 16 ohm load, you might get a
little more than 100 watts out of it.

The inverse resistance rule assumes that the power supply
voltage sets a pretty strict limit on the output voltage the
amplifier can deliver. So if you double the load
resistance, that same voltage will produce only half the
load current, so about half the power. What this misses is
that the supply voltage sags as it is loaded, and driving
higher resistance loads, it will sag less.

 

[Eeyore]

The power of amplifiers is given in relation to the impedance of the
speakers ( 200W @ 8 ohms).

Since I want to bye an amplifier and connected to a coil with grater
impendence I will need the following info:

Does any of you know how to estimate the power output for grater
impendence of a commercial amplifier.

Is the relation between Ohms and Watts linear so I can extrapolate to
the required impendence from the data given from the manufacturers?

Yes, the watts reduce almost linearly with the increase in impedance when
it's above 8 ohms.

So if the amp is 200W into 8 ohms, it'll be typically about 120W into 16
ohms. It's not usually quite as bad as half the power since the lightly
loaded power supply won't 'droop' so much on load as with 8 ohms.

Graham