# How would I test the output wattage of a reciever?

Discussion in 'Home Theater Projects' started by Aaron_Morris, Mar 24, 2003.

1. ### Aaron_Morris Well-Known Member

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I have an older model Kenwood receiver (model number KRA-4010) that I have had no luck finding wattage info (or any other info for that matter). I was curious if anyone has had any luck with estimated output of an amplifier, and if so how was it done?
I was considering using some test tones I have collected, sine waves of differant frequencies and pink noise, and a DMM to try and get a rough estiamte of the voltage output on AC. Is my thinking right here, or will this simply not work.

Thanks for any help.

2. ### Janne Ahonen Member

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Janne Ahonen
Aaron,

Assuming your multimeter frequency response is flat, then you can measure maximum output voltage from the amplifier. Outputs are connected into desired load, and then the output level is increased until desired distortion level occurs at the amplifier output(s). Then, the output voltage is measured, and power is calculated based on that voltage. Assuming sine signal input, power can be calculated using P = U^2/Z, where P is power in watts, U is RMS voltage measured across the load and Z is the load impedance (modulus, if using reactive load).

Loading of the amplifier during measurement is important, because power supply is one of the reasons which limit maximum power when the load impedance is lowered.

Greatest difficulty here is finding when distortion has reached some level. Simplest criteria is to measure output voltage just before output signal clips at top or bottom. But this requires oscilloscope or similar equipment.

Regards,
Janne

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4. ### Aaron_Morris Well-Known Member

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Thanks for the info about the MM measuring method.

And as for Brian Foley, that is not the one that I have. Missing an "A" in the model number. The unit that I have is a decently modern looking unit. All black with one jog dial on the left hand side and a small LCD screen with no other gauges.

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