Martin Audio – MA1.6s Amplifier
E
NGLISH
11
6.7 Power
consumption
There are three ways to determine the power/current consumption of the amplifier:
First
, the peak current draw at full output power. Under this condition the power amplifier will operate for less than
2 minutes before thermally limiting or blowing the mains fuse, and is an unrealistic ënormalí use condition. To
design a mains distribution system based on the current draw at full power would result in an over specified
system. No programme material requires the full steady state continuous power of an amplifier, this operating
condition is only used for amplifier bench testing.
Second,
the maximum expected average current under worst-case program material, which is 1/3 of full power
according to the FTC-standard. At this level the music will be in a state of constant clip and is therefore the highest
power level that can be obtained without completely obliterating the program material.
Last
, the "normal operating power", as defined by EN 60065, IEC 65/ANSI/UL 6500 as a measurement level for
approval and testing to these standards. The normal operating power is measured using pink noise, with an
average output power equal to 1/8 of full power. The one-eighth power is the maximum level music can be re-
played without continuous amplifier clipping; this corresponds to headroom of only 9dBs, which is very low for
normal program material.
6.7.1
Calculation
The current draw
can be calculated by dividing the mains input power by the mains voltage.
We recommend you to design the power distribution for at least the current at 1/8 power, and 1/3 power for heavy-
duty demands such as concert touring and industrial music etc.
The heat power
can be calculated as follows:
If a headroom figure of 5dB (1/3 of full power) is used, with a 4 ohms load on each output of the amplifier. The
power per channel is 840 / 3 = 280 watts, and the total output power = 2 x 280 = 560 watts.
The power consumption according to the chart above is then 1330watts.
The heat power produced
is the difference between the power consumption and output power;
1330 - 560 = 770 watts total for the amplifier.
MA1.6s HEAT POWER
1/3 POWER
1/8 POWER
1/3 POWER
1/8 POWER
1/3 POWER
1/8 POWER
WATTS
Kcal/hour
BTU/hour
8 Ohm
443
373
380
320
1510
1270
4 Ohm
770
630
660
540
2630
2150
2 Ohm
1400
1100
1200
950
4780
3750
1/3 Power level = Average power with music as programme source. The amplifier driven to clip level
1/8 Power level = Normal operating power with music as programme source, 9dB headroom
Power
1/3 Power
1/8 Power
Idle
[W]
note 1
note 2
8 ohms
2x
430
730
480
115
4 ohms
2x
840
1330
840
115
2 ohms
2x
1200
2200
1400
115
Average power with music as program source. The amplifier driven to clip level.
Normal music power with 9dB headroom, IEC standard power rating.
MAX OUTPUT POWER
All material © 2007. Martin Audio Ltd. Subject to change without notice.
