Lab.gruppen LAB 300 User Manual

USER MANUAL HEADLINES

Unpacking 2

Warnings 2

User responsibility 2

1. Speaker damage

2. Speaker output hazard.

3. Radio interference.

Introduction 3

1. Front panel

2. Rear panel

Installation 4

1. Mounting

2. Cooling

3. Operating voltage

4. Grounding

5. Power consumption

6. Input connections

7. Connecting speakers

Operation modes 6

1. Stereo

2. Tandem mono

3. Bridged mono

4. Stereo reverse

Operation 7

1. Operation precautions

2. Input attenuators

3. Gain switch

4. Indicators

Protections 8

1. Clip-limiter

2. Thermal protection

3. VHF protection

4. Short circuit protection

5. D.C. protection

USER MANUAL

LAB 300

Design features 9

•

Safety approvals

• EMC approvals

Specifications 9

•

EMC-declaration

Appendix A 10

•

Mains voltage selection

Troubleshooting 10

Warranty and disclaimers 11

• General

• International

Technical assistance and services 11

• International

• Factory services

1

Unpacking

Carefully open the shipping carton and check for
any noticeable damage. Every LAB.GRUPPEN
amplifier is tested and inspected before leaving the
factory and should arrive in perfect condition. If
found to be damaged, notify the shipping company
immediately. Only the consignee may institute a
claim with the carrier, for damage incurred during
shipping. Be sure to save the carton and packing
materials for the carrier's inspection.
It is also advisable, to save the carton and packing
material, even if the amplifier is undamaged.
Should you ever need to ship the amplifier, use the
original packing.

Warnings

Read this before you are operating your amplifier:

• Do not use this amplifier if the power cord is
broken or frayed.

• Always operate the unit with the chassis
ground wire connected to the electrical safety
earth.

• Do not parallel or series connect an amplifier
output, with any other amplifier output. Do not
connect the amplifier output to any other
voltage source, such as battery, mains source,
or power supply, regardless of whether the
amplifier is turned on or off.

• Do not run the output of any amplifier back
into another channel's input.

• Do not block the air intake or exhaust ports.
Do not operate the amplifier near heat
producing devices such as radiators, stoves etc.

• Do not spill water or other liquids into or on
the unit. Do not operate the amplifier if
suspected or standing in liquid.

• Do not remove top or bottom covers. Removal
of the cover will expose hazardous voltages.
There is no serviceable parts inside and
removal may void warranty.

• Keep this manual for future reference.

User responsibility

1. Speaker damage
Your amplifier is very powerful and can be
potentially dangerous to both loudspeakers and
humans alike. Many loudspeakers can be easily
damaged or destroyed by overpowering, especially
with the high power available from a bridged
amplifier. Always check the speakers continuous
and peak power capabilities.
Even if the gain is reduced by using the amplifier's
front panel attenuator, it is still possible to reach
full output power, if the input signal level is high
enough.

2. Speaker output hazard
Power amplifiers are capable of producing
hazardous output voltages. To avoid electrical
shock, do not touch any exposed speaker wiring,
while the amplifier is operating. See page 6 about
outputs for proper connection of speakers.

3. Radio interference

This product has been tested, and complies with the
limits for the European Electro Magnetic
Compatibility (EMC) directive. These limits are
designed to provide reasonable protection against
harmful interference between electrical equipment.
However, there is no guarantee for no interference
even if the amplifier is EMC approved.
If the amplifier cause interference, which can be
easily determined by turning the amplifier on and
off, the user can correct the interference by one or
more of the following steps:

1. Increase the proximity between the equipment.

2. Connect the AC cord to an outlet on a different
circuit from that to which the affected unit is
connected.

3. If a radio receiver is interfered (normally
amplitude modulation); reorient the antenna.

4. Check if the affected unit complies with the
EMC limits for immunity, (CE-labelled).

If not, address the problem with the manufacturer
or supplier. All electrical products sold in the EC
must be approved for immunity against
electromagnetic fields, high voltage flashes, and
radio interference.

2

Introduction

Thank you for purchasing a LAB.GRUPPEN power amplifier. This manual contains important information on
operating your amplifier correctly and safely. Please take some time and read this manual to familiarize yourself
with the amplifier.

The front panel

Figure 1. Front panel

1. Carry/protection handle

Both handles can be used to carry the amplifier, they
also act as protection for the front panel. If so desired
they can be removed (by removing the screws behind
the front panel and replacing the handles with nuts)
for fixed installations, or racks where the front
covers are to shallow.

2. Input level attenuators

These controls are used to alter the signal level
entering the amplifier. They are calibrated in dB to
help set up active loudspeaker systems or cut down
unwanted noise from the input signal.
(See page 7).

3. Protect indicator (Temperature and VHF)

This indicator is lit if the amplifier tries to operate
above its maximum operating temperature (90
The indicator first comes on as a warning, to either
turn down the input level, or check the cooling
arrangements after what point

o

C).

The rear panel

the amplifier will mute the input signal. When the
cooling has returned the output heat sinks to the
normal operating temperature, the input signal is
unmuted.
This indicator also lights when constant signals,
above 20 kHz at full power, are present at the output
terminals. When this happens the input signal is
muted and the process cycles until the VHF signal is
no longer present. (See page 8).

4. Clip/limit indicator

This indicator tells when the amplifier output is
clipping or limiting. The two different states can be
told apart:

• When the clip limiter is engaged it flickers
briefly. (See page 8).

• When the clip limiter is not engaged it lights for
a longer period.

5. Power actuator

This is used to start the amplifier. (See page 4 and 7).

Figure 2. Rear panel

3

Please refer to diagram on page 3

1. Speaker connector

This type of speaker connector may be unfamiliar to
some users. A full description is found in the
operation section. (See page 6).

2. AC line cord (See page 5).

3. Clip limiter switch

Turns the clip limiter on and off. (See page 8).

4. Input jack

Alternative to using input XLR or for linking inputs
with other amplifiers. (See page 5).

Installation

1. Mounting

The amplifier is one rack unit high (1U) and will
mount in a standard EIA 19 inch rack. Amplifiers
may be stacked directly on top of each other. There
is no need for spacing between units. If it is the
intention to fill a rack with amplifiers, we
recommend racking is started from the bottom of
the rack. It is also recommended that rear supports
are used for amplifiers mounted in the middle of the
rack, especially if used as part of a portable system.

2. Cooling

Should a heat sink get too hot, its sensing circuit
will mute the hot channel. If the power supply
overheats, another sensing circuit will mute both
output channels, until it cools down to a safe
operation temperature.
Make sure that there is adequate air supply in the
rack and that the space at the rear allows the
exhaust to escape.
For fixed installations with a central cooling
system, usually found in fixed installations with a
dedicated rack room, it may be necessary to
calculate the maximum heat emission. Refer to
Power consumption on page 5.

3. Operating voltage

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.
For converting a 230 volt amplifier to 115 volt or
vice-versa, see Appendix A.

5. Input signal XLR (See page 5).

6. Phase reverse switch for channel B

For reversing the input signal phase of channel B to
allow bridged operation. (See page 7).

7. Link switch

Allows a single input to drive both channels
simultaneously. (See page 6).

8. Gain select switch

Allows amplifier gain to be switched between 23dB
and its normal gain at 0.775mV input sensitivity.
(See page 7).

The amplifier is supplied with an approved European
AC line connector. If this connector is not
appropriate for your country, it can be cut off and
wired to a suitable connector in the following way :

BROWN LIVE

BLUE NEUTRAL

GREEN/YELLOW EARTH

Once the AC connector is connected to a suitable AC
supply, the amplifier can be started with the AC
actuator.

4. Grounding

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 presents itself
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 cord.
For all units that are EMC 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.

5. Power consumption

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 trip the

4