Benchmark DAC3 HGC - Page 48

Instruction Manual for DAC3 HGC and DAC3 L with 2.X Firmware Page 48
Graph 2 - Low Frequency FFT - AC Line-Related Hum
The DAC3 shows no evidence of AC line-related hum to a measurement limit of about -160 dBFS.
The cursors are placed at 60 Hz and 180 Hz (frequencies where we would expect to see
interference from the 60 Hz AC input. In the idle channel noise spectrum there is absolutely no sign
of any AC hum! At full output, these line-related frequencies still measure better than -133 dB (see
Graph 4
).
This graph demonstrates one of the advantages of switching power supplies. The switching power
supplies in the DAC3 operate at frequencies above the audio band and this eliminates the strong
line-frequency magnetic fields that would have been created by line-frequency power transformers.
Audio Precision
DAC3 - FFT Idle Channel Noise - Low Frequency, 0 dBr = 0 dBFS = 27.5 dBu
DAC3 - FFT Idle Channel Noise - Low Frequency.at27
Color
Sweep Trace Line Style
Thick Data Axis
Comment Cursor1 Cursor2
1 1 Green Solid 4 Fft.Ch.1 Ampl Left
Left Channel *-160.182 dBr *-158.092 dBr
1 2 Red Solid 4 Fft.Ch.2 Ampl Right Right Channel -159.850 dBr A -160.611 dBr A
-160
+0
-140
-120
-100
-80
-60
-40
-20
d
B
r
A
-160
+0
-140
-120
-100
-80
-60
-40
-20
-160.182
-158.092
d
B
r
A
25
400
50 75
100
125 150
175
200
225
250
275 300
325
350
375
59.4129
180.626
Hz
dx=121.213 Hz
dy=+2.090 dB