Operation Manual
5. Operation and performance
16
C SERIES Operation Manual rev 3.0.0
adjust system settings and thereby avoid problems. In the rare event that conditions are extraordinarily severe, the
amplier will shut down until the fault or problem setting has been rectied or adjusted. These sensing circuits are
also employed to feed back voltage and current level information, via a side chain, to the limiters. Sensing circuits
also transmit local amplier module temperature and power supply temperature to the appropriate protection
mechanisms. Read the Protection, Faults and Warnings section for further details.
5.3.2. Headroom, sensitivity and VPL / Gain settings
The input amplier 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 a C 68:4 with an 8 ohm load and 141 V peak
(max.) and 42 V peak (min.) respectively for the eight different gain stages between +23 dB and +44 dB. The
resulting output power is displayed in dBu, Vrms and Watts in the tables to the far right. Complete input sensitivity
tables for all VPL and Gain settings for as applicable to 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 V
peak and +20.4 dB at 42 V peak. These lines illustrate the additional signal level that can be accepted at the input
before any signicant distortion will appear at the input stage.
NOTE: 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 amplier to clip level, you are in
danger of clipping the input stage before the current or voltage peak limiters are activated.
NOTE: When bridging two channels, you must add +6 dB to the input sensitivity to achieve maximum
output voltage due to the automatic -6 dB gain compensation inserted by the amplier.