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Operation Manual
Micro-Tech Series Power Amplifiers
page 22
This section provides detailed information
about the amount of power and current drawn
from the AC mains by Micro-Tech amplifiers
and the amount of heat produced under various
conditions. The calculations presented here are
intended to provide a realistic and reliable
depiction of the amplifiers. The following
assumptions or approximations were made:
• The amplifier’s available channels are loaded,
and full power is being delivered.
• Amplifier efficiency at standard 1 kHz power
is estimated to be 65%.
• Typical quiescent power draw for the Micro-
Tech 600 is 65 watts; typical quiescent power
draw for the Micro-Tech 1200 and 2400 is 80
watts.
• Quiescent thermal dissipation equals 222
btu/hr at 65 watts and 273 btu/hr at 80 watts.
• The estimated duty cycles take into account
the typical crest factor for each type of source
material.
• Duty cycle of pink noise is 50%.
• Duty cycle of highly compressed rock ‘n’ roll
midrange is 40%.
• Duty cycle of rock ‘n’ roll is 30%.
• Duty cycle of background music is 20%.
• Duty cycle of continuous speech is 10%.
• Duty cycle of infrequent paging is 1%.
Here are the equations used to calculate the
data presented in Figures 9.1, 9.2 and 9.3:
The quiescent power draw figures provided in
the opposite column are typical and include
power drawn by the fan. The following equation
converts power draw in watts to current draw in
amperes:
The power factor of 0.83 is needed to compen-
sate for the difference in phase between the AC
mains voltage and current. The following equa-
tion is used to calculate thermal dissipation:
The constant 0.35 is inefficiency (1.00–0.65)
and the factor 3.415 converts watts to btu/hr.
Thermal dissipation in btu is divided by the
constant 3.968 to get kcal. If you plan to mea-
sure output power under real-world conditions,
the following equation may also be helpful:
9 AC Power Draw and
Thermal Dissipation
AC Mains Power
Draw (watts)
=
Total output power with all
channels driven (watts)
x
Duty
Cycle
Amplifier Efficiency (.65)
+
Quiescent Power
Draw (watts)
Current Draw
(amperes)
=
AC Mains Power
Draw (watts)
x
AC Mains
Volta
g
e
Power
Factor
(
.83
)
Total output power with all
channels driven (watts)
Thermal
Dissipation
(btu/hr)
=
+
Quiescent Power
Draw (watts)
x
Duty
Cycle
Amplifier Efficiency (.65)
()
x
3.415
.35
x
Total measured output power
from all channels (watts)
Thermal
Dissipation
(btu/hr)
=
+
Quiescent Power
Draw (watts)
.35
x
Amplifier Efficienc
y
(.65)
()
x
3.415