Lab.gruppen fP 3400 - Manual (Page 13)

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 the state of constant clip and is
therefore the highest power level one can obtain without completely obliterating the program.
Last, the "regular operating power" as defined by the safety standard IEC 65/ANSI/UL 6500 and used
by a majority of safety agencies. The regular operating power is measured by using pink noise, and with
an average output power equal to 1/8 of full power. The one eighth of the total power is as loud as you
can play music while making some attempt to avoid obvious clipping. It also corresponds to a headroom
of 9dB, which is very low for regular audio program.
Power 1/3 Power 1/8 Power Idle
[W] note 1 note 2
fP 3400 8 ohms 2x 1100 1060 530 115
4 ohms 2x 1500 1440 685 115
2 ohms 2x 1700 1720 845 115
note 1 Average power with music as program source. The amplifier driven to clip level.
note 2 Normal music power with 9dB headroom, IEC standard power rating.
MAINS INPUT POWER MAX OUTPUT POWER
Table 3
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The heat power can be calculated as in the following example:
We consider a headroom of at least 5dB (1/3 of full power) and a 4 ohms load on an amplifier
producing 1500 watts per channel. The 1/3 power per channel is accordingly 1500 / 3 = 500 watts, and
total output 2 x 500 = 1000 watts.
The power consumption according to the chart above is then 1975 watts. This chart shows the active
power consumption of the amplifier with different loads and power levels.
The heat power produced is the difference between the power consumption and output power:
1440 - 1000 = 440 watts per amplifier.
The chart below shows the heat power produced in watts, in kcal per hour, and also in BTU per hour.
1/3 Power(1)1/8 Power (2) 1/3 Power(1) 1/8 Power (2)1/3 Power(1)1/8 Power (2)
[W] [W] kcal / h kcal / h BTU / h BTU / h
fP 3400 8 ohms 327 255 280 220 1120 870
4 ohms 440 310 380 270 1500 1060
2 ohms 587 420 500 360 2000 1430
note 1 Average power with music as program source. The amplifier driven to clip level.
note 2 Normal music power with 9dB headroom, IEC standard power rating.
HEAT POWER
The efficiency can also be calculated, it being the output-power divided by the input-power:
1000 watts / 1440 watts= 69%.
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