Lab.gruppen LAB 500 User Manual

Page 10

Design features

Cooling
The LAB.GRUPPEN amplifier runs very cool due
to a patented heat sink called Intercooler

. The

output devices (bi-polar) are mounted directly on a
copper heat sink thereby avoiding thermal losses
normally found when using mica washers (the heat
sink is mounted horizontally in front of a pressure
chamber) The air flow is constant along the whole
heat sink, thanks to a horizontal pressure chamber in
front of it, (in a conventional tunnel design the end of
the heat sink opposite to the fan invariably gets hotter
than that directly in front of the fan). When cool air
hits the geometric fins of the Intercooler

turbulence is produced thereby enabling efficient
cooling.

Safety approvals
Lab.Gruppen amplifiers are designed to meet the
IEC65, a stringent electrical safety approval from the
International Electro-technical Commission. The
IEC65 is recognized world-wide with most countries
having an equivalent.

EMC approvals
EMC stands for Electro Magnetic Compatibility. This
implies that the equipment should have low emission
of radio frequencies, directly as electromagnetic fields
in the air, and as conducted from the cables from and
to the unit. The unit should also be able to handle
electromagnetic fields, high voltage flashes, and radio
interference, coming into the unit via the air or cables.
Emission
The regulation now cover the frequency range from
150 kHz to 300 MHz. The maximum level radiated
from a unit has to be below 100

µV, ( 0.0001 V ).

Immunity
The equipment should be able to handle three
different types of interference:
• Electrostatic discharges up to 8 kV, hitting the

chassis or cables.

• Transients and bursts up to 1 kV, conducted

through the cables to the unit.

• Electromagnetic fields up to 3 V/m, radiated on

the unit and the cables in the frequency range of

27 - 500 MHz.
We have extended the tests in two cases and chosen a
standard used for heavy industrial situations. First, we
have tested conducted disturbances in the frequency
range 150 kHz - 80 MHz, by injecting 3V amplitude
modulated (80%) signals into all the cables ( inputs,
outputs and mains ). This covers noise from AM
transmitters, which are still in use in some areas.
Secondly, we have extended the range for
electromagnetic fields to 26 - 1000 MHz, with a level
of 6 V/m and 80% AM modulated.
In the range 895 - 905 MHz, we test with a field
strength of 35 V/m and 100% pulse modulation. This
emulate the signals from a mobile phone close to the
unit. In all cases the noise plus distortion is below 1%,
at normal operation level, ( normal operation level is
1/8 of full power or -9 dB under clip point according
to IEC 65).

EMC-declaration

This audio power amplifier conforms with the
EMC-directive 89/336/EEC and relates to the
following standards:
EN 55013:1990
EN 50 082-1

IEC 801-2, ed.1(1984)
IEC 801-3, ed.1(1988)
IEC 801-4, ed.1(1984)
SS-ENV 50 141 ed.1 (1994)