L-Acoustics LA48A, Руководство пользователя

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L-ACOUSTICS LA48a Manual V1.0 27/01/2003 12
5.5 POWER CONSUMPTION
There are three ways to define the power/current consumption of a power amplifier:
First , the peak current draw at full output power. Under this condition the power amplifier will trip
the mains breaker within 30 seconds and the amplifier will operate for less than 2 minutes before
thermally limiting. It is therefore meaningless to state the input power at full power since the heat
power at full power will be limited by the protection circuits. In practice, there are no audio program
materials which produce sustained full output power (only sine wave signals for test purposes).
However, if the amplifier is operated at sustained full power (using a sine wave signal) into low
impedances, the LA48a has a mains current limiter called
AFS (Automatic Fuse Saver), which will
limit the long-term current draw. Please see Section 8.5 for more detail concerning the AFS-limiter.
It is more useful to state the
current draw for different loads and output power levels. The current
draw is stated in Amperes (rms) and this figure corresponds to the value of the mains fuse required.
Table 3: LA48a Current Draw @ 4 ohms
Operating Condition Current Draw in Amperes (rms)
Idle state (no load) 1 A (rms)
1/8 of full power (- 9 dB) 6 A (rms)
1/3 of full power (-5 dB) 14 A (rms)
Full power (0 dB) at 1 kHz, 1% THD 20 A (rms), AFS limited
Second, the maximum expected average current under worst case conditions, corresponding to 1/3
full power program material 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 one can obtain without completely obliterating
the program material.
Third , the normal operating power, as defined by the safety standard IEC 65/ANSI/UL 6500 and used
by a majority of safety agencies. The normal operating power is measured using pink noise, with an
average output power equal to 1/8 of full power. The 1/8 full power specification is as loud as you can
play music while making some attempt to avoid obvious clipping and corresponds to 9 dB of
headroom (which is very low for normal audio program).
Table 4: LA48a Maximum Output Power versus Mains Input Power
MAXIMUM OUTPUT POWER MAINS INPUT POWER
Load # of ch Power AFS activated 1/3 Power 1/8 Power Idle
(watts) (watts) (see note 1) (see note 2)
8 ohms 2X 1300 1300 1230 575 105
4 ohms 2X 2300* 1450 1975 900 105
2 ohms 2X 2900* 1850 2950 1290 105
* Will be reduced by AFS protection
note 1 Mean power with music as program source (amplifier driven to clip level)
note 2
Normal music power with 9 dB headroom (IEC standard power rating)
It is recommended that you specify your power distribution service to ensure sufficient current for at
least 1/8 power operation and to upgrade service to meet 1/3 power requirements for heavy duty
demands like discos etc.