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Saturday, March 24, 2012
Zhaolu D1.3 headphone amp section RMAA
Because why not.
Xonar DX @ 80/100
For unloaded and 300Ω load: Output volume = 1.85V
For 16Ω load: Output volume = 0.7V
Max output power into 16Ω = 30mW
Output impedance @ 0.7V into 16Ω: Less than 0.4Ω
The 7kHz and 21kHz noise of my setup is again present. Also present is 50Hz and 150Hz coming from my network switch's power adapter which I was too lazy to turn off. Also present is a ~80Hz and ~240Hz noise coming from I don't know where. All these noise contributed to the noise level and lowered the amp's measured performance, so please manually look at the graphs for a more accurate picture.
Detailed RMAA results
Zhaolu D1.3 amp unloaded
Zhaolu D1.3 amp 300 ohm
Zhaolu D1.3 amp 16 ohm
One thing I learnt from measuring different amplifiers, it is that it is common for properly-designed amps to have good performance. Here we are looking at <0.001% THD @ 1.85V into 300Ω and higher loads, and IMD that is pretty decent too and screwed by the noise, which from my experience adds to the IMD numbers (and THD if it is a multiple of 1kHz). If you compare the noise and THD graphs, you'll find that the tallest peaks share the same frequencies.
Noise level of -100dB. If you disregard the 50Hz/80Hz/7kHz noise and their harmonics we might be getting -110dB. Still, noise that exists is noise that exists, regardless of the setup. A good equipment should be more noise-immune. Plus I'm using the power supply that is supposed to be used with the amp so this is indeed the amp's performance.
Crosstalk into unloaded and 300Ω is good (relative to noise level) but IMO can be better. Crosstalk into 16Ω is relatively decent. Power into 16Ω is a tad low for a desktop amp but that is to be expected from an amp powered by NE5532 and nothing else.