Tesira Operation Manual

11. Operation and performance
24
D SERIES Tesira Operation Manual rev 1.0.0
11.3. Amplifier and Load Protection Systems
The D Series is equipped with a comprehensive set of protection circuits. If operating conditions become
sufciently extreme that any of these circuits become active, indication is provided by amber or red LEDs on the
front panel, and by text notications in the Tesira software and CAFÉ software. Refer to Section 14.1 for more
information on warnings and faults.
11.3.1. Inter–Sample Voltage Peak Limiter (ISVPL)
The ISVPL is a high quality voltage limiter that can deliver seamless limitation to any desired level. It ensures that
the voltage at the output terminals never exceeds the dened threshold. It operates on these principles:
• The signal is delayed slightly to allow the ISVPL to look–ahead and reduce the gain before voltage in excess
of the threshold can appear at the output. This results in zero voltage overshoot at the output with a rounded
limitation up to the threshold.
• The amplitude of the output signal between digital samples is predicted which permits the ISVPL to respond to
analog peaks that may occur at the digital to analog converter.
• The release time of gain reduction is adaptive depending on the dynamics of the signal. It is possible to select
different ISVPL proles for limiting optimization for a specic frequency band and personal preference. The
proles are divided into two categories, with one category optimized for low distortion and the other focusing
on producing high sound pressure level (SPL). Within each category there are proles optimized for the different
frequency bands.
11.3.1.1. Low Distortion Profiles
• Universal – The universal prole is a soft limiter that can be used for all frequencies and is conservative in its
action upon VCL and CPL.
• Sub/LF – The Sub/LF prole is tuned for frequency bands below 600 Hz. It has longer attack and release times
and is less conservative when it comes to acting upon VCL and CPL.
11.3.1.2. High SPL Profiles
High SPL proles do not use the adaptive release time feature. High SPL proles optimized for high frequencies
use less of the look–ahead delay peak–rounding feature; this feature is used most in the Sub prole and least the
HF prole.
• Sub – The Sub prole is optimized for frequencies between 20 – 200 Hz
• LF – The LF prole is optimized for frequencies between 20 – 1200 Hz
• MF – The MF prole is optimized for frequencies between 300 – 6000 Hz
• HF – The HF prole is optimized for frequencies above 1 kHz
Table 11.3 shows the theoretical maximum output power for a given load impedance and ISVPL setting.