Audio Research High Definition Reference 80S User Manual page 18

Operation
Power
Turns power of Reference 80S on or off.
GhostMeter™ Light
Adjusts meter light LED display brightness
to one of four levels of brightness
including "off".
Tube Monitor
Allows checking the operation of each of
the four KT 150 output tubes (V1-V4). The
LED associated with each output tube will
illuminate when operating properly. See
Auto Bias section under Operation for
further explanation of its operation.
Pentode/Triode
Allows selecting pentode (approximately
70 watts per channel) operation –
indicated by green color of LED
above this function button, or triode
(approximately 35 watts per channel)
operation – indicated by blue white color
of the power-on LED.
Auto Bias
The Reference 80S incorporates a highly
sophisticated auto-bias circuit. There
are no user-adjustable bias controls.
There should never be a need to check
or adjust the auto-bias circuit: once it is
factory set, no additional adjustment is
required. The auto-bias circuit will 'lock in'
the idle current of each bank of two KT150
output tubes approximately two minutes
after the Reference 80S is turned on, and
continually compensates to maintain the
proper bias as the tubes age. Auto-bias
sets the idle current at 65mA per tube.
18
It is always recommended owners
purchase replacement tubes from Audio
Research Corp. While the auto bias
adjusts the idle current of each of the four
KT150 output tubes, matched tube sets
will provide optimum performance and
longest tube life.
The auto bias circuit will not
accommodate output tubes with
extremely high or low plate current
readings. Aftermarket tubes may not be
tested to the same rigorous standards
as Audio Research tests, so care must
be exercised when installing aftermarket
tubes. If uncertain about aftermarket tube
requirements, please contact service@
audioresearch.com for recommendations.
Audio Research supplies the KT150 output
tube in the Reference 80S, providing the
highest power and best sound possible in
this amplifier design.
Audio Research has tested the Reference
80S with KT120, KT88 and 6550WE
output tubes. The Reference 80S will
produce less power with any of these
tubes and the sound will be degraded.
Under no circumstances should any tube
not electrically equivelant to the KT150,
KT88 or 6550WE be installed. Tubes
such as the EL34, KT77, 6L6 should never
be installed. Installing tubes such as
these will void the factory warranty and
Audio Research will not be liable for any
damage. Contact service@audioresearch.
com if you have questions regarding tube
compatability.