It was time to take the 814 SE Class A2 amplifier measurements. The challenge though, is that the amp is so heavy that I will never take it up to the workshop. Therefore, I decided to take my workshop PC down from the loft this time to see how the 814 really responded.
First test was to do a THD analysis as a function of the total output power. As you don’t want to do this with your speakers, and also the classic wire wound resistors (Alu-clad) are inductive, you want to use non-inductive resistors like this test jig:
I bolted on to a large heat-sink an array of resistors to form 8Ω in value by using a pair of 10Ω in parallel and three 1Ω in series. I added a set of binding posts and connectors for the speaker cables. this way you can easily wire your speakers and connect your audio test set to take the measurements.