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Power Calculations - No Clipping

Posted by Satelliteman (A) on September 17, 2006 at 15:06:26

Can anyone advise me how , or what method is used to establish the Power rating of the amplifiers ( specifically the Mk60 breed )
I have used two meters measuring both P/P & RMS waveform on a back to back large wirewound resistive load . Load resistance is 8 ohms ..., ( ie ...two resistors 4 ohm each , wired opposite directions ..so to hopefully cancel the inductance of the load . ( hope I have got that correct for starters )
Next , I biased the amps to 500mA only ( clamped input / 0 mV ) ...then passed a 1kHz sinewave to the input ...whilst watching the output waveform on the Scope . I noted the point at which clipping occurs , then backed off until a perfect waveform is present , ,then measured the P/P from the scope , and also the RMS VAC values from the Fluke meter . I measured a value of 18 volts AC RMS ...from the Fluke , also I measure the P/P and divided it by 0.707 ...which equalled a similiar value . The Voltage RMS is approx 18 VAC RMS ...so then I did a equation of IxI / R ....or I squared divided by Resistance ...this gave me 40 watts rms . This seems well off from the 60 Watts I was expecting . Not that I need 60 watts - but what frequency is used for this measurements , and how are they done ??
Can anyone explain - I would like to do it properly .
Stu

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