VISTEK V1638 analogue audio
distribution amplifier
10
Issue 8
3.3
Gain Adjustment
The V1638 has two rotary panel switches for adjusting the gain of each channel. These panel switches only
have effect when the
REM
/
LOCAL
switch is in the
LOCAL
position. The
COARSE
switch adjusts the gain in 8dB
steps from -96dB (mute) to +24dB. The
FINE
switch adjusts the gain in 0.5 dB steps from coarse setting dB
to coarse s 7.5dB. The table below shows the correspondence between the 16 switch positions
and the gain setting for both coarse and fine controls.
Coarse switch
Fine switch
Switch
Gain value
Switch
Gain value
setting
(dB)
setting
(dB)
0
-96 (mute)
0
0
1
-88
1
+0.5
2
-80
2
+1.0
3
-72
3
+1.5
4
-64
4
+2.0
5
-56
5
+2.5
6
-48
6
+3.0
7
-40
7
+3.5
8
-32
8
+4.0
9
-24
9
+4.5
A
-16
A
+5.0
B
-8
B
+5.5
C
0
C
+6.0
D
+8
D
+6.5
E
+16
E
+7.0
F
+24
F
+7.5
It can be seen from the table that the gain applied is the sum of the settings of the
COARSE
switch and
the
FINE
switch. Care should be taken when setting the gains in an application to allow sufficient
headroom so that the V1638 does not clip on peaks. Remember that the maximum output of the V1638
is +28dBu. The V1638 circuitry updates the gain setting from the panel switches every 50 ms. When
the rem/local switch is set to the rem position, the gain set on the front panel switches is ignored and
the gain is set from the DART interface. On the standard version, gain resolution from the remote
interface is 0.5dB, and on the high resolution version it is 0.25dB.
