PRE420 Instruction Manual – rev. E
Page 21
Wideband THD+N vs. Frequency
Measurement Bandwidth = 10 Hz to 500 kHz, Gain = 30 to 60 dB, Output Level = +4 dBu
Audio Precision
02/19/07 16:16:11
PRE420 - Wideband THD+N vs Frequency, BW=500 kHz
Color
Sweep
Trace
Line Style
Thick
Data
Axis
Comment
1
1
Red
Solid
4
Anlr.THD+N Ratio
Left
60 dB Gain (top trace)
2
1
Magenta
Solid
4
Anlr.THD+N Ratio
Left
50 dB Gain
3
1
Blue
Solid
4
Anlr.THD+N Ratio
Left
40 dB Gain
4
1
Green
Solid
4
Anlr.THD+N Ratio
Left
30 dB Gain (bottom trace)
0.001
0.1
0.002
0.005
0.01
0.02
0.05
%
-100
-60
-98
-96
-94
-92
-90
-88
-86
-84
-82
-80
-78
-76
-74
-72
-70
-68
-66
-64
-62
d
B
20
200k
50
100
200
500
1k
2k
5k
10k
20k
50k
100k
Hz
This graph shows that THD+N does not rise above noise – even at very high frequencies. The 500
kHz measurement bandwidth elevates the noise by 28 dB relative to a 20 kHz measurement
bandwidth.
