Testing an amplifier

[Martin vd Ban]

Hi there,

 

I've got an amplifier but I'm a bit suspicious of it not delivering the power it is supposed to give. How can I check this?

 

Greetings,

Martin vd Ban

[j_b]

Using Ohms law,

 

Power = Volts * Volts / Resistance

 

So, a 1kW amplifier, into 8 ohms

 

1kW = ? * ? / 8

 

or ? * ? = 8000

 

therefore

 

at 1kW, expect to see about 90 volts across the load.

 

Of course, remember that this is constant - i.e. a 1kHz sinewave into the load (speaker) which is pretty darned loud if it's 1kW.

 

I use a suitable dummy load (made of resistors) when testing amplifiers, rather than loadspeakers, as it's a little more sociable. Make sure that whatever you use to measure the voltage across the load is suitable for the frequency that you use to test at. Some cheap multimeters are designed for 50-60Hz operation, and not much cop at 1kHz say.

 

Hope this helps