So, this is very odd. I received a dummy load in the mail today. Measuring output impedance seems pretty straightforward. Use my multimeter to measure output voltage, attach dummy load, repeat, calculate. To test how easy this was, I used my Clip+, and consistently get the same measurements. I calculated a 1.06 ohm output impedance, improved my connection and got 1 on the dot. Pretty much right on where you would expect. Output voltage is low, as you'd expect. But it's plenty high enough to get a reliable measurement, exactly what I would expect from something putting out 10mW.
So I moved on to the ZX1, and it's output voltage is just vanishingly low. I'm using a 1000Hz test signal, and I just can't get a measurement that's worth noting. It's so damn low I can't reliably calculate the output impedance. I can tell you that it's between 0 and 8 ohms. Every measurement has been one or the other. Loaded, I basically get .0001V and I get .0001 or .0002V with no load. Is there something about a class D amp that might lead to what I'm seeing? Any way, knowing that the wattage is about the same as the Clip+, if the voltage is much lower, there must be a lot more current, but I also measure more current from the clip+. So I thought, maybe the headphone jack isn't outputting anything, so I plugged in some headphones, and that's not the case. None of this makes any sense.
I've used the multimeter enough to know what I'm doing, but this is the first time I've used a dummy load. But again, I've not had trouble with the aforementioned Clip+, or my E18 (which I measured at 1.78 ohm output impedance when set to low gain, if anyone's interested.)
Edited by reginalb - 3/18/14 at 2:46pm