Benchmark HPA4 - Page 34

Instruction Manual for HPA4 with 1.0.X Firmware – REV B Page 34
Graph 3 - THD vs. Output Power - Headphone Amplifier - 0 to 6 W into 16-Ohms
The THX-888 headphone amplifier is designed to drive heavy loads at high levels without an
increase in THD. It is also virtually distortion-free at low signal levels and/or light loads.
This output power sweep shows that THD does not increase with output power. The THX-888
headphone amplifier stays extremely clean as the output power is swept from 60 mWatts to 6
Watts. Over this 100:1 range of power, the THD is virtually unchanged! The THD measures better
than about -125 dB (0.000056%) over this wide range of output power into a 16-Ohm load. At the
maximum rated output power or 6 Watts, THD measures about -127 dB (0.00004%).
This test demonstrates the effectiveness of the THX AAA™ technology in the THX-888 amplifier.
Notes:
• The scale on the left is dB THD relative to the output level.
• The test tone is 1 kHz. The test tone level was varied to sweep the output power from 0.06
Watts to 6 Watts.
• Balanced inputs to headphone outputs, volume control set at 0 dB.
Audio Precision
07/16/18 09:26:27
THDvsPowerl_BAL_IN_HPA_Out_16_Ohms.at27
ColorSweep Trace
Line Style Thick Data
Axis Comment
1
1 Green Solid
4
Distortion.Ch.1 Harm Sum1 Ratio Left
-130
-100
-128
-126
-124
-122
-120
-118
-116
-114
-112
-110
-108
-106
-104
-102
d
B
0
6 500m
1
1.5 2 2.5 3 3.5
4
4.5 5
5.5
W