9 AC Power Draw and Thermal Dissipation; Operation Manual; Thermal Dissipation- Page 21

Micro-Tech Series

 Power Amplifiers

page 21

Operation Manual

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

Voltage

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 Efficiency (.65)

(

)

x 3.415