Where would you measure temp?

I second Herman's comment. The question is unanswerable without knowing what location on the particular amplifier the spec is defined for.

The only temperature specs for amplifiers that I can recall seeing are either for ambient temperature (i.e., the temperature of the surrounding environment), or for the heat sink temperatures in the specific case of some of the Pass Labs amps. The manuals for some of the Pass Labs amps talk about heat sink temperatures being about 25 degC above ambient (i.e., typically 50 degC or so), with thermal protection mechanisms kicking in at 75 degC.

Regards,
-- Al

Richard, I took a look at some pictures showing various Spectral amps with the top cover removed, including the DMA-360 which I suspect is what you've got, based on the current limit spec. There is a large, thick, light-colored rectangular metal plate (aluminum?) just inside the rear panel, adjacent to the heat sinks on the rear, which appears to be where the output transistors are mounted. I suspect that the thermal sensor(s) is/are mounted somewhere on that plate.

Taking the reading with the cover removed, though, would presumably lower the temperature somewhat. My guess would be that measuring from the outside instead, on the rear panel at the base of the heat sink fins, would provide a reasonably good approximation.

Keep in mind also that since this apparently is not a Class A design the temperature will rise considerably if music is played at high volume for a significant amount of time, compared to the temperature for no signal conditions.

Regards,
-- Al