Decided I needed a better test load, so I built one.
A bit more versatile than just a big resistor on some binding posts, it has a few features:
- Two completely independent channels, optionally paralleled with a switch
- Each channel switchable between 3.75, 7.5, 15 and 30 ohms
- BNC outputs for monitoring as well as 10:1 attenuated BNCs for all outputs
- Outputs include a direct singled ended monitor, as well as two separately earthed outputs to monitor bridged amplifiers or perform impedance measurements with the load in series with the DUT.
- Chassis earth brought out to a post to earth to where is strategic for the particular testing situation if noise issues crop up.
Each resistor is 50W rated and the heatsinks were salvaged from an old MOSFET PA amp. I don't intend to run the resistors near their power rating, if I did I would probably point a big fan at the thing.
The attenuated outputs have an output-Z of approx 900 ohms but this shouldn't pose an issue with a short run of coax to a scope or audio interface.