PLM Series Operation Manual rev 1.1.3
7. Operation and Performance
27
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
2.67
4
8
16
ISVPL SETTING (V
peak)
193
9312
6984
4656
2328
1164
181
8190
6143
4095
2048
1024
167
6972
5229
3486
1743
872
153
5852
4389
2926
1463
732
121
3660
2745
1830
915
458
101
2550
1913
1275
638
319
83
1722
1292
861
431
215
70
1225
919
613
306
153
56
784
588
392
196
98
47
552
414
276
138
69
38
361
271
181
90
45
17.8
79
59
40
20
10
Table 7.3.1: ISVPL-to-output examples
