Here are THD and SINAD measurements from three recent reviews, each of these three headphone amplifiers was tested using a different signal level; the Topping L30 at 2V, the Topping A90 at 4V, and the THX AAA 789 at 6V.
This represents as much as 12dB difference in input signal level between the L30 test and the AAA 789 test.
In the Topping L30 review it states that the gain was set to Unity (2V in / 2V out), but it is unclear if the A90 was adjusted to produce 4V out and the AAA789 to produce 6V out.
Are the output levels of each DUT normalized to "0dBA" as shown in the FFT?
How would these measurements compare if fed from the same signal level?
TOPPING L30:
Headphone Amplifier Audio Measurements
As usual, I feed the amp a superbly high quality analog 1 kHz tone at 2 volts, set the volume/gain to output 2 volts ("unity gain") and see how much distortion and noise we get:
TOPPING A90:
Headphone Amplifier Audio Measurements
With a million headphone amplifiers out there, measurements is the only way to find the good from bad. So let's start with our usual dashboard of unity gain (same voltage output as input). Connection is XLR input and unbalanced 1/4 headphone out unless said otherwise:
DROP THX AAA 789:
Measurements
For consistency with my last couple of headphone amplifier reviews, I set the output at about 5.7 volts:
This represents as much as 12dB difference in input signal level between the L30 test and the AAA 789 test.
In the Topping L30 review it states that the gain was set to Unity (2V in / 2V out), but it is unclear if the A90 was adjusted to produce 4V out and the AAA789 to produce 6V out.
Are the output levels of each DUT normalized to "0dBA" as shown in the FFT?
How would these measurements compare if fed from the same signal level?
TOPPING L30:
Headphone Amplifier Audio Measurements
As usual, I feed the amp a superbly high quality analog 1 kHz tone at 2 volts, set the volume/gain to output 2 volts ("unity gain") and see how much distortion and noise we get:
TOPPING A90:
Headphone Amplifier Audio Measurements
With a million headphone amplifiers out there, measurements is the only way to find the good from bad. So let's start with our usual dashboard of unity gain (same voltage output as input). Connection is XLR input and unbalanced 1/4 headphone out unless said otherwise:
DROP THX AAA 789:
Measurements
For consistency with my last couple of headphone amplifier reviews, I set the output at about 5.7 volts: