Amplifier And Load Protection Systems; Inter-Sample Voltage Peak Limiter (Isvpl) - Lab.gruppen PLM series Operation Manual

7.3 Amplifier and Load Protection Systems

The PLM is equipped with a comprehensive set of protection circuits. If operating conditions become suf-
ficiently extreme that any of these circuits become active, indication is provided by LEDs in one or more soft
function buttons 5-8, together with adjacent warning text. In addition to this, notification is also presented
within the Lake Controller software and within system log files.

7.3.1 Inter-Sample Voltage Peak Limiter (ISVPL)

The ISVPL is a high quality voltage limiter. Its purpose is to ensure that the voltage at the output terminals never
exceeds the threshold which has been set. It operates on these fundamental principles:
▸ The signal is delayed slightly in order to allow the ISVPL to "look ahead" and reduce the gain before any
voltage in excess of the threshold can appear at the output. This results in zero voltage overshoot at the
output.
▸ The amplitude of the output signal "between" digital samples is predicted. This permits the ISVPL to
respond to analog peaks that may occur at the digital to analog converter.
▸ The release time of any gain reduction is adaptive and is dependant on the dynamics of the signal. It
is also possible to select between different profiles, so that the limiting can be optimized for a specific
frequency band. The profiles are Sub/LF and Universal.
The table below represents the theoretical maximum output power for a given ISVPL setting and impedance
shown.
An ISVPL-to-load calculator that will assist in
generating the appropriate ISVPL setting for a
desired power load is available at
www.labgruppen.com/plm
MAX. SINEWAVE BURST POWER (Watts)
Load Impedance (ohms)
2
ISVPL SETTING (V peak)
193 9312
181 8190
167 6972
153 5852
121 3660
101 2550
83 1722
70 1225
56 784
47 552
38 361
17.8 79
Table 7.3.1: ISVPL-to-output examples
2.67 4 8 16
6984 4656 2328 1164
6143 4095 2048 1024
5229 3486 1743 872
4389 2926 1463 732
2745 1830 915 458
1913 1275 638 319
1292 861 431 215
919 613 306 153
588 392 196 98
414 276 138 69
271 181 90 45
59 40 20 10
7. Operation and Performance
PLM Series Operation Manual rev 1.1.3
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