Chapter 3 — Operation
Overload
BE 1300– 12 Dual Microphone Supply Type 5935 3–7
User Guide
creased by the required 26 dB. Note that the sensitivity control has a range of
±5 dB, so setting the gain to 20 dB and then trying to achieve a 26dB gain would
not succeed. Measurement of the 1V at the output of the Type 5935 could be done
using a measuring amplifier, for example Type 2636, using an oscilloscope, or using
metering on the equipment attached to the output.
The screwdriver sensitivity adjustments can also be used to accurately match the
levels of the two channels.
3.7 Overload
The overload warning LED lights when the output of the Type 5935 exceeds
5V rms. At this point non-linear distortions begin. If it is found that the overload
light frequently comes on during operation, the gain should be adjusted. In a meas-
urement situation changing the unit’s gain by 10 dB may be sufficient, and can
easily be accounted for in any calculation that has to be done.
If the gain is at –5 dB (the lowest gain) and overload still occurs, then the input
signal is too large. This should be attenuated in some way, for example by adding a
ZF 0020 20 dB passive attenuator just after the microphone capsule.
The overload circuitry comes before the A-weighting filter, so that overload indica-
tion is independent of frequency.
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