Studio Reference I Power Draw, Current Draw And Thermal Dissipation At Various Duty Cycles - Crown STUDIO AMPLIFIER Owner's Manual

7 AC Power Draw and
Thermal Dissipation
This section provides detailed information about the
amount of power and current drawn from the AC mains
by Studio Reference amplifiers and the amount of heat
produced under various conditions. The calculations
presented here are intended to provide a very realistic
and reliable depiction of the amplifiers. The following
assumptions were made:
• The amplifier's available channels are loaded, and
full, standard 1 kHz power is being delivered.
• Amplifier efficiency at standard 1 kHz power is
estimated to be 65%.
• Quiescent power draw is 90 watts (an almost
negligible amount for full-power calculations).
• Quiescent thermal dissipation equals 307 btu/hr at
90 watts.
• Duty cycle takes into account the typical crest factor
for a particular 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 uncompressed 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%.
8 Ohm Stereo / 16 Ohm Bridge-Mono / 4 Ohm Parallel-Mono
AC Mains
Duty
Cycle
Current Draw (Amps) Thermal Dissipation
Power
Draw
100-120 V 220-240 V btu/hr
(Watts)
Fig. 7.1 Studio Reference I Power Draw, Current Draw and
Thermal Dissipation at Various Duty Cycles
I I I I I
Here are the equations used to calculate the data pre-
sented in Figures 7.1 and 7.2:
The estimated quiescent power draw of 90 watts is a
maximum figure, and assumes the fan is running at
high speed. The following equation converts power
draw in watts to current draw in amperes:
The power factor constant of 0.83 is needed to
compensate for the difference in phase between in the
AC mains voltage and current. The following equation
was 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 dissipa-
tion in btu is divided by the constant 3.968 to get kcal. If
you plan to measure output power under real-world
conditions, the following equation may be helpful:
I
L O A D
4 Ohm Stereo / 8 Ohm Bridge-Mono / 2 Ohm Parallel-Mono
AC Mains
Current Draw (Amps)
Power
Draw
kcal/hr 100-120 V 220-240 V
(Watts)
II II II II II
Professional Studio Amplifiers
Thermal Dissipation
btu/hr kcal/hr