nanaholic
Headphoneus Supremus
- Joined
- Sep 2, 2010
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Have a look at ifi micro iDSD BL various mode (eco, normal and turbo), the correlation between various power and impedance.
Look at turbo mode output - 4000mW@16ohm, when you increase the impedance of the load by 4 (ie to 64ohm), the power output didn't drop by 4 times to 1000mW, instead it is 1560mW. Also for 600ohm using a linear correlation assumption the power output should be 106.67, but the actual output is 166mW, so obviously that's not a linear correlation when operating in turbo mode.
Normal and eco mode seems to have a linear correlation, but since the turbo mode doesn't exhibit a linear relationship thus you can't use that to infer a general law regarding power/impedance calculations. Rather this shows that you need more measurements to understand the actual behaviour of the device itself - because who knows, maybe the Walkman's Class D amp is more like turbo mode where efficiency gets better as load increases, but you can never know unless you measure it or when the manufacturer gives out more numbers.