Page 39
Macro-Tech 5002VZ
Power Amplifier
Reference Manual
7 AC Power Draw and
Thermal Dissipation
This section provides detailed information about the
amount of power and current drawn from the AC power
line by the Macro-Tech 5002VZ, and the amount of heat
produced under various conditions. The calculations
presented here are intended to provide a realistic and
reliable depiction of the amplifier. The following assump-
tions were made:
• The amplifier’s available channels are loaded, and full,
standard 1 kHz power is being delivered.
• Amplifier efficiency at standard 1kHz power is
estimated to be 73%.
• Quiescent power draw is 90 watts
• Quiescent heat dissipation equals 105 btu/hr at
90 watts.
• 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, short-duration paging is 1%.
8 Ohm Stereo / 4 Ohm Parallel-Mono
L O A D
50%
40%
30%
20%
10%
1,881
1,523
1,164
806
448
1,793
1,491
1,189
887
584
2,845
2,294
1,743
1,192
641
657
540
423
305
189
3,534
2,845
2,156
1,467
779
3,187
2,606
2,026
1,445
864
22.7
18.3
14.0
9.7
5.4
34.3
27.6
21.0
14.4
7.7
42.6
34.3
26.0
17.7
9.4
Duty
Cycle
AC Mains
Power
Draw
(Watts)
btu/hr
Current Draw (Amps)
10.3
8.3
6.4
4.4
2.5
15.6
12.6
9.5
6.5
3.4
19.4
15.6
11.8
8.0
4.3
4 Ohm Stereo / 8 Ohm Bridge-Mono / 2 Ohm Parallel-Mono 2 Ohm Stereo / 4 Ohm Bridge-Mono / 1 Ohm Parallel-Mono
Macro-Tech 5002VZ
452
376
300
224
147
kcal/hr
2,606
2,142
1,677
1,212
748
803
657
511
364
218
100-120 V 220-240 V
Thermal Dissipation
btu/hr
Current Draw (Amps)
kcal/hr
100-120 V 220-240 V
Thermal Dissipation
btu/hr
Current Draw (Amps)
kcal/hr
100-120 V 220-240 V
Thermal Dissipation
AC Mains
Power
Draw
(Watts)
AC Mains
Power
Draw
(Watts)
Fig. 7.1 Power Draw, Current Draw and Thermal Dissipation at Various Duty Cycles
Here are the equations used to calculate the data pre-
sented in Figure 7.1:
The following equation converts power draw in watts to
current draw in amperes:
The value used for Power Factor is 0.83. The Power
Factor variable is needed to compensate for the differ-
ence in phase between the AC mains voltage and cur-
rent.
The following equation is used to calculate thermal dis-
sipation.
The value used for Amplifier Inefficiency is 0.27 (1.00–
0.73). The factor 3.415 converts watts to btu/hr. Ther-
mal dissipation 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 also be helpful:
