Headroom, Sensitivity And Vpl / Gain Settings - Lab.gruppen C 68:4 Operation Manual

7.3. headroom, sensitivity and VPL / Gain
settings
The input amplifier and limiter system is designed to
accommodate extremes of performance. Typically,
exceeding maximum input by much as +10 dB will
only result in a 1% increase in distortion. The
following schematics illustrate how the adjusable
VPL and Gain circuitry affect input sensitivity and
output power:
The tables to the left of the drawing below, show
input sensitivity for C 68:4 with an 8 ohm load and
141 Vpeak (max.) and 42 Vpeak (min.) respectively
for the eightdifferent gain stages between +23 dB
and +44 dB. The resulting output power is displayed
in dBu, Vrms and Watt in the tables to the far right.
Complete input sensitivity tables for all VPL and
Gain settings for all C Series models, can be found
at www.labgruppen.com.
The headroom available through the input stage to
the clip limiter is shown by the dotted lines as +10
dB at 141 Vpeak and +20.4 dB at 42 Vpeak. These
lines illustrate the additional signal level that can be
accepted at the input before any significant distortion
will appear at the input stage.
Input Amplifier
Gain select switches
VPL set to 141 V
peak
Input
sensitivity Gain set to:
(DIP-switches)
dBu / V
rms
+ 44 dB
-2,0 / 0,6
+ 41 dB
1,0 / 0,9
4,0 / 1,2 + 38 dB
7,0 / 1,7 + 35 dB
10,0 / 2,5 + 32 dB
+ 29 dB
13,0 / 3,5
+ 26 dB
16,0 / 4,9
+ 23 dB
19,0 / 6,9
VPL set to 42 V
peak
Input
sensitivity Gain set to:
(DIP-switches)
dBu / V
rms
+ 44 dB
-12,3 / 0,2
+ 41 dB
-9,3 / 0,3
+ 38 dB
-6,3 / 0,4
+ 35 dB
-3,3 / 0,5
+ 32 dB
-0,3 / 0,7
+ 29 dB
2,7 / 1,1
+ 26 dB
5,7 / 1,5
+ 23 dB
8,7 / 2,1
Level control Clip Limiter
Dynamic
Front panel
potentiometer Gain reduction
+10 dB headroom to clip,
relative to input sensitivity *)
Complete tables for all VPL
settings can be found at:
www.labgruppen.com
+20,4 dB headroom to clip,
relative to input sensitivity *)
*) Headrom limited to +8dB at Gain set to +23 dB at Max. VPL
OPERATION AND PERFORMANCE 7
The headroom available through the input stage to
the clip limiter is shown by the dotted lines as +10
dB at 141 Vpeak and +20.4 dB at 42 Vpeak. These
lines illustrate the additional signal level that can be
accepted at the input before any significant distortion
will appear at the input stage.
If you use the level potentiometer in the
signal chain to reduce the level by an amount
greater than the headroom relative to input
sensitivity, AND you drive the amplifier to
clip level, you are in danger of clipping the input stage
before the current or voltage peak limiters are
activated.
When bridging two channels, you must ad
+6 dB to the input sensitivity to achieve
maximum output voltage due to the
automatic - 6 dB gain compensation
inserted by the amplifier.
Voltage Peak Limiter
VPL select switches
Hard/Soft switch
Voltage Clip sensing
Current clip sensing
Voltage Peak
Limiter set to:
(DIP-switches)
141 V
peak
118 V
peak
100 V
peak
85 V
peak
71 V
peak
59 V
peak
50 V
peak
42 V
peak
C Series Operation Manual 15
Output Power Amplifier
Class TD
Control Mute
Monitoring Level
Temperature
Fault/Warning
Output Output
power power
Watt
dBu / V
rms
42,2 / 100 1200 W
40,7 / 84 880 W
39,2 / 71 630 W
37,8 / 60 440 W
36,2 / 50 310 W
34,7 / 42 220 W
33,1 / 35 160 W
31,8 / 30 110 W