Benchmark HPA4 - Page 42

Instruction Manual for HPA4 with 1.0.X Firmware – REV B Page 42
Graph 11 - FFT Idle Channel Noise - Balanced In to Headphone Out
This graph shows the noise performance of the HPA4 from the balanced inputs to the output of the
THX-888 headphone amplifier. This extraordinary performance keeps noise at inaudible levels,
even when using high-efficiency headphones.
Notes:
• The scale on the left (dBr A) is dB relative to +28 dBu. This is the maximum input and
output level supported by the HPA4 line stage.
• The scale on the right (dBr B) is dB relative to +22 dBu. This is the input level required to
drive an external AHB2 power amplifier to full output power. It is also the level required to
drive the internal THX-888 to full output power.
• Balanced inputs to headphone outputs, volume control set at 0 dB.
Audio Precision
07/13/18 10:03:10
FFT_Idle_Unity_Gain_Bal_HPA.at27
Color
Sweep
Trace Line Style Thick
Data Axis Comment
Source 2
1 2 Green Solid 4
Fft.Ch.1 Ampl Left Left HP Output : 7.00000 =Swr.Ch. A Input
1
3 Green
Solid 4
Fft.Ch.1 Ampl Right
: 7.00000 =Swr.Ch. A Input
2 2
Red Solid 4
Fft.Ch.1 Ampl Left Right HP Output
: 8.00000 =Swr.Ch. A Input
2
3 Red Solid
4 Fft.Ch.1 Ampl Right
: 8.00000 =Swr.Ch. A Input
-170
+0
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
d
B
r
B
-180
+0
-170
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
d
B
r
A
2.5k 47.5k 5k 7.5k
10k
12.5k 15k
17.5k 20k
22.5k 25k
27.5k
30k 32.5k
35k 37.5k 40k 42.5k 45k
Hz