Benchmark LA4 - Graph 7: FFT 1 kHz Tone (22 dBu Balanced)

Instruction Manual for LA4 with 1.0.X Firmware – REV A Page 35
Graph 7 - FFT 1 kHz Tone at 22 dBu - Line Amplifier - Balanced to Balanced
This plot shows that the THD produced by the line amplifier is extremely low, even when delivering
a very high 22 dBu output. The third harmonic measures better than -124 dB (0.00006%) on all
balanced outputs! The 5th harmonic measures better than -141 dB (0.000009%) on all balanced
outputs!
Notes:
• The scale on the left (dBr B) is dB relative to +22 dBu. This is the signal level required to
drive an external AHB2 power amplifier to full output power.
• Balanced inputs to balanced line outputs, volume control set at 0 dB.
• The 1 kHz fundamental has been removed using a notch filter. This filter increases the
resolution of the AP2722 test system.
Audio Precision
07/13/18 10:57:04
FFT_1kHz_Bal_Bal.at27
ColorSweep
Trace Line Style Thick Data Axis
Comment
Source 2 Cursor1
Cursor2
1
2
Green
Solid 4
Fft.Ch.1 Ampl Left Left Line Out
: 1.00000 =Swr.Ch. A Input -124.094 dBr B
-146.609 dBr B
2 2
Red Solid 4
Fft.Ch.1 Ampl Left Right Line Out
: 2.00000 =Swr.Ch. A Input -126.729 dBr B
-141.285 dBr B
3
2 Yellow Solid 4
Fft.Ch.1 Ampl Left Mono Line Out
: 3.00000 =Swr.Ch. A Input *-128.219 dBr *-144.566 dBr
-190
+0
-180
-170
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
-128.219
-144.566
d
B
r
B
2k 32k
4k 6k 8k 10k
12k 14k
16k
18k 20k
22k
24k 26k
28k 30k
3.01493k
5.01822k
Hz
dx=2.00329 kHz
dy=-16.347 dB