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Propeller Head Plaza: RE: Amplifier power meter? by psn

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RE: Amplifier power meter?

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Get a bare meter
Look up its reference current (the max current to present full scale deflection (FSD))
Determine its connection polarity (so it does not move the wrong way)
Use a terminal strip with screw connections
Use resistor (appropriate for your amp's power)
Use a diode oriented so it prevents the signal polarity from driving the meter backwards

Experiment with very low power while confirming that only the unblocked polarity of the signal through the diode drives the meter in the full scale deflection direction.

Experiment with resistor values or do the math with the FSD current in mind - gradually increasing power

Use smart phone SPL measure and rated speaker sensitivity to approximate amp power output against meter deflection - adjust amp volume and resistor until deflection registration on face is near FSD at very loud or rated power - if printed scale figures don't match calculated power levels, print your own meter face scale or just live with it

Make copy for other channel


*** Cautions***

Start off with large value resistors and work down
The meters I used were scaled for 250W at "full 0dB" with the red zone extending to 300W, but they had a secondary scale maxing to 30W with 1W about dead center... that was the useful scale for my amp
I connected my meters to the "B" set of speaker outputs (so they were in parallel with the "A" set of main speakers), and set the speaker selection to "A+B" when I wanted to view the meter

No guarantees that you won't find a fire extinguisher to come in handy :)



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Topic - Amplifier power meter? - Mike K 11:14:31 06/30/20 ( 23)