power equal to 1/8 of full power. The one-eighth power is the maximum
volume music can be re-played without continuous amplifier clipping.
It also corresponds to headroom of 9dB, which is very low for normal
program material.
If operating the amplifier into a sustained 2 ohm load, protection circuits
within the amplifier will limit the long-term current draw, and thermal
protection may occur.
Table 1.
The current draw can be calculated by dividing the mains input power by
the mains voltage. We recommend that you design the power distribution
for at least the current at 1/8 power or 1/3 power for heavy duty demand
like discos etc.
The heat power can be calculated as the following example:
If we consider a headroom of at least 9dB and a 4 ohm load on an amplifier
producing 2100 watts per channel. The 1/8 power per channel is then;
2100 ÷ 8 = 263 watts, total output; 2 x 263 = 525 watts.
The power consumption according to the chart above is then 1300 watts.
The heat power produced is the difference between the power
consumption and power output; 1300 - 525 = 775 watts per amplifier.
Martin Audio – MA4.2 Power Amplifier
E
NGLISH
8
MAX OUTPUT POWER
MAINS INPUT POWER
Power
Full Power
1/3 Power
1/8 Power
Idle
sine wave
note 1
note 2
MA4.2
8 ohms
2X
1300
3500
1400
800
130
4 ohms
2X
2100
6000
2300
1300
130
2 ohms
2X
3600
10300*
4300
2300
130
* Will be reduced by AFS protection.
note 1 Average power with music as program
note 2 Normal music power with 9dB headroom,
source. The amplifier driven to clip level.
IEC standard power rating.
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