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Amplifier load

  • This is an 8 ohm load to test power amplifiers. The goal is to automate THD+N calculations using REW and a big resistor block.

    I have been using a pair of 200W, 8ohm, resistors that were sourced from eBay.

    resistor block resized.jpg

    This project will move forward in three steps. First, will be a cooling enclosure with a switchable fan and banana jack test points. The second step will add an MCU fan controller with over-heat warning, etc. The third step (stretch goal) will calculate dissipated power using the MCU. I have a 16 bit ADC that I plan to use for the purpose of creating an active power display.

    Long term, I may add relays to disconnect the resistors if they overheat.

    The case is designed to be 1/2 rack width and generally match the dimensions of a 1/2 rack piece of test equipment, like a multimeter, arb gen, etc. It will be 3d printed.

    Rear fan mounted.

    resized_rear panel on tube.jpg

    Front view. The load fits in the lower chamber. The upper chamber is for the MCU and wiring.

    resized_rear panel installed front view.jpg

    The enclosure is designed in FreeCAD. I'm happy to share the source, if anyone is interested.

    This project is about to stall because I will be away for a few months but I will circle back next spring and post further updates.
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