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Load Monitoring – What For and How
Overview
Ti Series
All the
amplifiers incorporate sophisticated load monitoring facilities
that may be used for general feedback of the connected load conditions, or
programmed to provide simple go/no-go status.
The system has been optimised to work with steady state stimuli – that is either a
continuous tone, or pink noise.
The real time monitoring of load impedances using program material (either voice
or music) is inadvisable due to the great variability of driver impedance with
frequency.
Rather than specify nominal impedance for a driver for the amplifier to compare
against, the amplifier continuously measures the connected load and the user
specifies the value when happy with the value. In this way, when a specific test
tone is used, the actual impedance of the driver can be captured at this frequency
without needing to know the impedance response of the speaker.
The system is designed to work with output levels in the region of 1V and 100mA,
equating to an output power of approximately 100mW. This value has been
chosen to facilitate both continuous monitoring (traditionally using a very high
frequency low level tone > 17kHz) or sequenced burst testing using spot
frequencies (chosen depending on the driver/system connected) or pink noise.
Also note that, in order to stabilise the impedance readings sufficiently, there will
be approximately 5 seconds of delay between load changes showing up in the
software and these changes triggering a load error.
Amplifier Operator's Manual
The impedance plot shown
here is that of a typical
low frequency driver with
a specified nominal
impedance of 8 ohms.
At the driver's main
resonant frequency, shown
by the red line, the
impedance rises to over
17.5 ohms, whilst the
minimum impedance is
4.95 ohms.
Page 45
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