Lab.gruppen fP 6400 - Manual (Page 12)

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WARNING!
A label just below the mains cable on the rear of the amplifier indicates the AC mains voltage for
which the amplifier is wired. Connect the power cable only to the AC source referred to on the
label. The warranty will not cover damage caused by connecting to the wrong type of AC mains.
Lab.gruppen switch mode amplifiers use primary switching. The mains power is being rectified directly
in front of the transformer, meaning that the power supply is insensitive to the mains frequency and will
operate from DC to 400 Hz.
If the power plug is not appropriate for your country, it can be cut off and wired to a suitable connector in
the following way:
BLACK or BROWN
LIVE
WHITE or BLUE
NEUTRAL
GREEN or GREEN/YELLOW
EARTH
Once the AC connector is connected to a suitable AC supply, the amplifier can be started with the power
switch. When you power up the amplifier it takes a couple of seconds to check its circuits (this is known
as the "soft start" or "slow start" sequence), the fans then blow at high speed before going into "idle", and
the two bottom green LED’s come on to show the output circuits are receiving the correct rail voltage.
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There is no ground lift switch or terminal on this amplifier. The signal ground is always floating via a
resistor to chassis, and the grounding system is automatic. If a potential above 0.6V is presents in between
signal ground and chassis ground, a short circuit is introduced between the two, thereby enabling electrical
protection. If a unit in the system is faulty, its mains fuse will blow due to this automatic ground system.
If however you wish to tie the signal ground to chassis, connect the XLR-connector’s shell lug to pin 1. In
the interest of safety never disconnect the earth pin on the AC power cord.
For all units that are FCC approved (radio interference), there is an AC mains filter. This filter needs the
chassis ground for reference, otherwise a current loop is formed via the signal ground.
Use the balanced input to avoid hum and interference.
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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 will blow the mains
breaker within 30 seconds, or the amplifier will operate for less than 2 minutes before thermally
limiting. Therefore it is meaningless to state the input power at full power. The heat power at full power
will anyway be limited by the protection circuits. There is no audio program material producing steadily
full output power; it would be only sine wave for test purposes.
In case of the amplifier being operated at sustained full power (such as sine wave) into low impedances,
the fP 6400 offers a mains current limiter called AFS
TM (Automatic Fuse Saver), which will limit the
long-term current draw. Read more about the AFS limiter under “Protection” on page 16 . There is also a
Technical Note on our website www.labgruppen.com : AFS limiting and power consumption.
It is more useful to state the current draw in different loads and output power levels. These figures can
be found on the specification sheet. The current draw is measured in Ampere rms. This figure
corresponds to the minimum value of the mains fuse needed.
We recommend you to design the power distribution at least for the current at 1/8 power, and for 1/3
power for heavy-duty demands like discotheques, etc.
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
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