Audio Research Reference 250, Руководство пользователя

Страница: 5 / 9

5
If the unit is to be operated in an enclosure
such as an equipment rack, make certain
that adequate air flow above and to each
side of the unit is provided. The “ambient”
operating
temperature should never
exceed 120º F or 49º C. Improper installation
will cause premature tube failure and will
affect your warranty, as well as the service
life of the unit.
It is normal for a vacuum tube power
amplifier to run quite “warm”, and if used for
prolonged periods, “hot” to the touch. All
components within are, however, operated
at safe, conservative levels and will not be
improperly affected thereby, providing the
requirements outlined above are adhered
to.
Warnings
1. To prevent fire or shock
hazard, do not expose this
product to rain or moisture.
2. This unit operates on voltages which can
cause serious injury or death. Do not
operate with cover removed. Any
necessary servicing should be carried out
by your authorized Audio Research dealer
or other qualified electronics technician.
3 . Use only the plastic insulated screwdriver
included with this unit when making front
panel bias adjustments.
4. The power cord on this unit is safety-tested
and is equipped with a proper grounding
plug. If used normally, it will provide a safe
earth ground connection of the chassis.
Defeat of the grounding plug, or any
unauthorized modification of the active
circuitry
or controls of this unit,
automatically voids warranty coverage,
5. For safe operation and protection against
fire hazard, replace fuses only with those
of the same type and rating as those
supplied with this unit.
6. At 73 lbs. (33 kg) net weight per chassis,
the Reference 250 amplifier is too heavy
for one person to lift. To avoid injury, do
not attempt to unpack, lift or move the
unit without the help of at least one other
person.
7. Always mute the preamplifier when
cueing a phono cartridge stylus up or
down.
Due to the immense power supply reserves,
high power output, and wide bandwidth of
the Reference 250, added emphasis must
be placed on use of your preamplifier's
mute switch from a safety standpoint. A
transient signal burst or “pop” such as
caused by tonearm cueing, accidental
dropping or brushing of the phono cartridge
stylus–even at a normal listening level–could
cause an instantaneous peak power
demand on the amplifier of up to 1000 watts
(which the Reference 250 will try to deliver).
The importance of lowering the preamplifier
volume level to a minimum setting and
activating the mute switch whenever
cueing the tonearm or making contact with
the phono cartridge stylus cannot be
overemphasized.
Adhering to this
precautionary muting procedure is equally
important when turning your system on or
off, and when connecting or disconnecting
any cables in the system. Carefully following
this recommendation will minimize the
chance of causing undue stress and
potential damage to your amplifiers and
loudspeakers. (See your preamplifier
Owner's
Manual for more detailed
instructions on use of muting provisions.)
Description of Controls
Front Panel Control
POWER: Press the POWER switch to turn the
unit on, indicated by a lit green LED directly
above the switch. When turned on, there is
an automatic warm-up sequence which
lasts for approximately 45 seconds before
the unit is operational.
FAN: Press the FAN switch to select low (dim
Power LED) or high (bright Power LED) for fan
speed setting.
LIGHT: Press the LIGHT switch to select high,
low, or no meter illumination.
BIAS (Adjustment Procedure):
NOTE: Amplifier should be turned on and
operating for at least 30 minutes prior to
adjusting bias of the output tubes.
Press BIAS switch once and the V1 output
tube LED is illuminated with its bias level
indicated on the front panel meter. Adjust
V1 tube bias level with the plastic flat-
bladed bias tool (provided), inserted in the