6
CHAPTER 2
NOTE: Refer to Appendix B for details
on the MICA loudspeaker’s AC voltage
requirements.
After applying AC power, the proper operating voltage is
automatically selected, but the system is muted. During the
next three seconds the following events occur:
1. The primary fans turn on.
2. The main power supply slowly ramps on.
3. The green Active LED on the user panel lights up,
indicating that the system is enabled and ready to pass
audio signals.
CAUTION: If the Active LED does not
illuminate or the system does not respond
to audio input after ten seconds, remove AC power
immediately. Verify that the voltage is within the
proper range. If the problem persists, please contact
Meyer Sound or an authorized service center.
If voltage drops below the low boundary of either safe
operating range (brownout), MICA uses stored energy to
continue functioning briefly, and shuts down only if voltage
does not rise above the low boundary before MICA’s
storage circuits are depleted. How long MICA will continue
to function during brownout depends on the amount of
voltage drop and the audio source level during the drop.
If the voltage increases above the upper boundary of
either range, the power supply rapidly turns off, preventing
damage to the unit.
NOTE: If voltage fluctuates within either
operating range, automatic tap selection
stabilizes the internal operating voltage. This tap
selection is instantaneous, and there are no audible
artifacts.
If MICA shuts down due to either low or high voltage, its
power supply automatically turns on again after three
seconds if the voltage has returned to either normal
operating window. If the MICA loudspeaker does not turn
back on after 10 seconds, remove AC power immediately
(see previous Caution).
NOTE: It is recommended that the supply be
operated in the rated voltage windows at least
a few volts away from the turn on/off points. This
ensures that AC voltage variations from the service
entry — or peak voltage drops due to cable runs
— do not cause the amplifier to cycle on and off.
CURRENT REQUIREMENTS
The MICA loudspeaker presents a dynamic load to the AC
mains, which causes the amount of current to fluctuate
between quiet and loud operating levels. Since different
cables and circuit breakers heat up at varying rates, it is
essential to understand the types of current ratings and how
they correspond to circuit breaker and cable specifications.
The maximum long-term continuous current is the
maximum rms current during a period of at least ten
seconds. It is used to calculate the temperature increase
in cables, in order to select a cable size and gauge that
conforms to electrical code standards. It is also used to
select the rating for slow-reacting thermal breakers.
The burst current is the maximum rms current during a
period of approximately one second, used to select the
rating of most magnetic breakers and to calculate the peak
voltage drop in long AC cables according to the formula:
V pk (drop) = I pk x R (cable total)
The ultimate short-term peak current is used to select the
rating of fast-reacting magnetic breakers.
Use Table 2.1 below as a guide when selecting cable gauge
size and circuit breaker ratings for your operating voltage.
Table 2.1: MICA Current Ratings
Current Draw 115 V AC 230 V AC 100 V AC
Idle current 1.1 A rms 0.55 A rms 1.3 A rms
Max. long-term
continuous
5.4 A rms 2.7 A rms 6.2 A rms
Burst current 8.7 A rms 4.3 A rms 10.0 A rms
Ultimate short-
term peak
24.6 A pk 12.3 A pk 28.3 A pk
NOTE: For best performance, the AC cable
voltage drop should not exceed 10 volts, or
10 percent at 115 volts and 5 percent at 230 volts.
Make sure that even with the AC voltage drop the
AC voltage always stays in the operating windows.
The minimum electrical service amperage required by a
MICA system is the sum of each loudspeaker’s maximum
long-term continuous current. An additional 30 percent
above the minimum amperage is recommended to prevent
peak voltage drops at the service entry.
CAUTION: In the unlikely event that the
circuit breakers on MICA’s user panel trip
(the white center buttons pop out), disconnect the
AC power cable. Do not reset the breakers with
the AC connected. Contact Meyer Sound for repair
information.
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