Audio Research LS28 - In Your System; A Note about Vacuum Tubes

7
Installation
In your system
• To ensure normal component life and
safe operation this unit must be operated
only in an upright position. Adequate
airow and proper cooling can occur
only if there is no restriction above and
behind the unit and on either side.
• The special non-marring elastomer feet
provide adequate spacing and stability
only on a smooth, hard surface, and also
assist to isolate the preamplier from
spurious vibrations. For upright stability
and best performance, never operate
the unit while it is sitting on a soft
surface such as a thick rug or carpet.
• Due to its weight, this preamplier must
be supported on a surface specically
rated for such a load. Check with the
manufacturer of your support system to
be sure it is rated to handle this weight.
• If the unit is to be operated in an
enclosure such as an equipment rack,
make certain that adequate airow
above and to each side of the unit is
provided. Audio Research recommends
a minimum of 6-8 inches (15-20 cm) of
clearance above the LS28 to maintain
proper ambient operating temperature.
• The ‘ambient’ operating temperature
should never exceed 30° C, 86° F.
Improper installation will cause premature
tube failure and will aect your warranty,
as well as the service life of the unit.
• It is normal for a vacuum tube preamplier
to run quite warm, and if used for
prolonged periods, hot to the touch. All
components within are operated at safe,
conservative levels well within tolerances.
A Note about Vacuum Tubes
The vacuum tubes in your LS28 have
been burned in, tested and electrically
matched to provide the best performance
and reliability of your preamplier. That
said, vacuum tubes must be replaced
from time to time. The 6H30 tubes in
the LS28 should have an expected life
of approximately 4,000 hours. This
life expectancy is only approximate.