Technical information

Macro-Tech 3600VZ Power Amplifier
Page 35
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 the Macro-Tech 3600VZ , 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 amplifier. The following as-
sumptions were made:
• The amplifier’s available channels are loaded, and full,
standard 1 kHz power is being delivered.
• Quiescent power draw is 90 watts (an almost
negligible amount for full-power calculations).
• 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%.
Here are the equations used to calculate the data pre-
sented in Figure 7.1:
AC Mains Power
Draw (watts)
=
Total output power with all
channels driven (watts)
x
Duty
Cycle
Amplifier Efficiency
+
Quiescent Power
Draw (watts)
The quiescent power draw of 90 watts is typical, and
assumes the cooling fans are not running.
Thermal
Dissipation
(btu/hr)
=
Quiescent Power
Draw (watts)
[]
x
3.415
( 1 – Power to Load ) +
or
Total output power with all
channels driven (watts)
Thermal
Dissipation
(btu/hr)
=
+
Quiescent Power
Draw (watts)
x
Duty
Cycle
x
Amplifier Efficiency
()
x
3.415
Amplifier
Inefficiency
The constant 3.415 converts watts to btu/hr. Thermal
dissipation in btu is divided by the constant 3.968 to
get kcal.
To convert the power draw in watts to current draw in
amperes, use the following equation:
Current Draw
(amperes)
=
AC Mains Power
Draw (watts)
x
AC Mains
Volta
g
e
Power
Factor
(
.83
)
The current draw values shown in Figure 7.1 depend
on the AC mains voltage (power draw and thermal dis-
sipation are typical for any AC power voltage).
*BM=Brid
g
e-Mono
,
PM=Parallel-Mono
Macro-Tech 3600VZ
8 Ohm Stereo
L O A D
50%
40%
30%
20%
10%
1545
1255
965
675
380
1300
1105
905
705
505
2160
1745
1330
920
505
435
365
295
225
150
2340
1890
1440
990
540
1845
1535
1230
920
615
15.5
12.6
9.6
6.7
3.8
21.6
17.5
13.3
9.2
5.0
23.4
18.9
14.4
9.9
5.4
Duty
Cycle
AC Mains
Power
Draw
(Watts)
btu/hr
Current Draw (Amps)
7.8
6.3
4.8
3.4
1.9
10.8
8.8
6.7
4.6
2.5
11.7
9.5
7.2
5.0
2.7
4 Ohm Stereo / 8 Ohm BM / 2 Ohm PM* 2 Ohm Stereo / 4 Ohm BM / 1 Ohm PM*
330
280
230
180
130
kcal/hr
1720
1440
1155
875
590
465
390
310
235
155
100-120 V 220-240 V
Thermal Dissipation
btu/hr
Current Draw (Amps)
kcal/hr100-120 V 220-240 V
Thermal Dissipation
btu/hr
Current Draw (Amps)
kcal/hr100-120 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