recommended Poweramp alpha 703/704 settings for V20, for now:
1. Audio/Output: native OpenSL ES or java AudioTrack, no difference, they all work at 16/48.
2. Audio/Advanced Tweaks: enable Direct Volume Control, it seems DVC can move digital volume control before resampler, instead of after resampler if you use system volume control. this makes following settings effective, and yields much better result than system volume control.
3. Audio/Resampler/Resampler Type: use SoX.
4. Audio/Resampler/Dither: this is tricky, you can choose between 2 options...
Shibata noise shaping: very clean sound. but noise gate on DAC does kick in frequently when signal is very weak at low volumes, resulting in slight gliches/pops.
Triangular with high pass: noise gate seldom activates in this mode. the downside is that you get a consistent white noise, not unlike some analog recordings.
RMAA test results:
20 ohms dummy load test at 45 to 75 volume levels (75 is the maximum volume on V20)
V20's distortion start to rise above volume level 50 on 20 ohms load, looks like being soft-clipped, maybe due to current limit.
crosstalk:
sweep frequency IMD:
10 ohms dummy load test at 35 to 75 volume levels
wow! it is massively overloaded at volume 75, spectacular!
100 ohms (detected as high impedance deivce) dummy load test at 35 to 75 volume levels.
10 ohms (in high impedance mode by hot swap) dummy load test at 15 to 75 volume levels.
it doesn't look like a good idea to override the auto detection...
summary of output voltage levels at different gain modes, measured by -3dB 1k tone with 10 ohms load
summary of distortion performance in low gain mode
(i tried to include high gain/aux mode in the same graph, but it seems high gain mode performs significantly worse than low gain mode for low impedance load even at the same output voltage level)
output impedance:
2.3 ohms for ESS ES9218 in all gain modes
3.8 ohms for Qualcomm WCD9335
just for fun, V20 in non-hifi mode into 10 ohms load
this time i want to learn about the differences between gain modes (other than gain factor, which is already measured above), and to determine what are the best gain modes for various loads.
each load is tested in all three gain modes, and all tests are voltage matched.
10 ohm load:
100 ohm load:
unloaded:
low impedance load works best in low impedance mode.
high impedance load works best in high impedance mode.
unloaded works best in line out mode.
1. Audio/Output: native OpenSL ES or java AudioTrack, no difference, they all work at 16/48.
2. Audio/Advanced Tweaks: enable Direct Volume Control, it seems DVC can move digital volume control before resampler, instead of after resampler if you use system volume control. this makes following settings effective, and yields much better result than system volume control.
3. Audio/Resampler/Resampler Type: use SoX.
4. Audio/Resampler/Dither: this is tricky, you can choose between 2 options...
Shibata noise shaping: very clean sound. but noise gate on DAC does kick in frequently when signal is very weak at low volumes, resulting in slight gliches/pops.
Triangular with high pass: noise gate seldom activates in this mode. the downside is that you get a consistent white noise, not unlike some analog recordings.
RMAA test results:
20 ohms dummy load test at 45 to 75 volume levels (75 is the maximum volume on V20)
V20's distortion start to rise above volume level 50 on 20 ohms load, looks like being soft-clipped, maybe due to current limit.
crosstalk:
sweep frequency IMD:
10 ohms dummy load test at 35 to 75 volume levels
wow! it is massively overloaded at volume 75, spectacular!
100 ohms (detected as high impedance deivce) dummy load test at 35 to 75 volume levels.
10 ohms (in high impedance mode by hot swap) dummy load test at 15 to 75 volume levels.
it doesn't look like a good idea to override the auto detection...
summary of output voltage levels at different gain modes, measured by -3dB 1k tone with 10 ohms load
summary of distortion performance in low gain mode
(i tried to include high gain/aux mode in the same graph, but it seems high gain mode performs significantly worse than low gain mode for low impedance load even at the same output voltage level)
output impedance:
2.3 ohms for ESS ES9218 in all gain modes
3.8 ohms for Qualcomm WCD9335
just for fun, V20 in non-hifi mode into 10 ohms load
this time i want to learn about the differences between gain modes (other than gain factor, which is already measured above), and to determine what are the best gain modes for various loads.
each load is tested in all three gain modes, and all tests are voltage matched.
10 ohm load:
100 ohm load:
unloaded:
low impedance load works best in low impedance mode.
high impedance load works best in high impedance mode.
unloaded works best in line out mode.
