In a past post, I’ve attached a picture of the load I was using for speaker amplifier testing. I have a box full of these 50W wire-wound resistors and a heatsink (HS) I’ve tapped to be able to attach these resistors easily. I was simply connecting as needed for the specific case. In practice, I rarely change the default 8×2-ohm resistors which are split into 2 loads of 8-ohm each. When I needed to dissipate significant power I would normally point a fan at that HS and be done with it. However, this wasn’t very convenient, and I wanted something more “user friendly” to replace it, this is what will be described in this post.
One tool I use quite often when testing amplifier is a dummy load. Because of that I have a large box of high power (50W) resistors, and a large heat-sink that is tapped for easy attachment of the resistors to it. I typically have 8 resistors of 2ohm each, connected according to the requirement of the measurement i’m doing at the moment. More often than not, they are wired as 2 independent 8ohm resistors to measure speaker amplifiers (see Fig. 1). However, when I need to measure headphone amplifiers, I typically only need lower power loads, and therefore use a couple of resistors from the spare parts box. This got frustrating over time, soldering the resistors to a TRS plug, then soldering/clipping on a couple of wires to the scope/other test instrument. Therefore I’ve decided to do a small side-project of building a simple dummy load box for headphone amplifiers testing.