Audio Research Reference 75 SE User manual

Reference 75 SE
H I G H D E F I N I T I O N ®

Thank You.
Thank you for choosing the
Reference 75 SE to be a part of
your high performance music
listening system. Since 1970,
Audio Research has been creating
some of the world’s nest
audio equipment. Each piece is
handcrafted in Minnesota, and has
been designed to provide many
years of listening enjoyment.
We understand you are eager
to begin listening; however,
please take a few minutes to
read through this guide for
useful information concerning
the operation of your new
amplier. Once installed, please
allow an appropriate break-
in period to fully appreciate
the benets this amplier will
provide to your system.
After reading the user guide, if
you have any further questions
regarding your amplier, contact
your dealer or Audio Research
customer service - they will be
happy to help you make the
most of your new component.
Happy Listening!

4
Contents
Warnings
Installation
Before Operating the Reference 75 SE
In Your System
Connections
Back Panel Controls and Connections
Input Connectors
Output Connectors
Matching
Remote Turn-on
A.C. Power Connection
5
6
7
8
9
9
9
10
11
Operation
Front Panel Controls and Displays
Start-Up
Shut-Down
Break-in
Display Brightness Adjustment
Output Tube Bias Adjust
12
13
13
13
13
14
Maintenance
Vacuum Tubes
Service
Cleaning
Disposal and Recycling Guidelines
Warranty
Specications
15
15
15
15
16
17

5
Warnings
To prevent re, or shock hazard,
do not expose your Reference
75 SE to rain or moisture.
Do not place objects containing
water on top of this unit.
This unit contains voltages which can cause
serious injury or death. Do not operate
with covers removed. Refer servicing
to your authorized Audio Research
dealer or other qualied personnel.
The detachable power cord on your
Reference 75 SE is equipped with a heavy
gauge, 3-conductor cable and a standard
three-prong grounding plug. For absolute
protection, do not defeat the ground power
plug. This provides power line grounding
of the Reference 75 SE chassis to provide
absolute protection from electrical shock.
The appliance coupler (a.c. power connector)
at the rear of this unit must be accessible
for emergency power disconnect.
For continued protection against re hazard,
replace the fuse only with the same type
and rating as specied at the fuse holder.
This unit is RoHS compliant.
A note about packaging...
Save all packaging in a dry place away from
re hazard. Your Reference 75 SE amplier
is a precision electronic instrument
and should be properly cartoned any
time shipment is made. You may not
have occasion to return your unit to the
factory for service, but if that should
prove necessary, or other occasion
requiring shipment occurs, the original
packaging will protect your Reference 75
SE from unnecessary damage or delay.

6
Before operating the Reference 75 SE
Your Reference 75 SE amplier is shipped
with the vacuum tubes packed in foam
blocks. These must be unpacked and
installed before you attempt to operate the
amplier. Included are two matched pair
of KT150 output tubes, and two 6H30 dual
triodes used in the input stage. Proceed
according to the following instructions.
Installation
Remove all screws fastening the top cover.
Carefully remove each vacuum tube
from its protective foam and match its
location ‘V’ number (written on the base
of the tube) to the ‘V’ number printed
next to each socket. Firmly seat each
tube in its matching socket, taking care
to ‘key’ the tube pins to the socket holes.
Retain the foam blocks with other packing
materials for possible future use.
Refasten top cover on amplier.
V2 V1 V4 V3
V5 V6
FRONT
REAR
TUBE LOCATIONS
TOP VIEW
4 KT150
2 6H30

7
In your system
To insure 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 ampli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 ampli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.
The ‘ambient’ operating temperature should
never exceed 120° F or 49° C. 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 power
amplier 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 aected
thereby, providing the requirements
outlined above are adhered to.
Installation

8
Connections
5A FUSE
SLO-BLO
T4A (230V)
IN OUT
+12V REMOTE
TURN ON
REFERENCE 75
STEREO AMPLIFIER
VOLTS
SERIAL
048
LEFT INPUT
PLYMOUTH, MINNESOTA
MADE IN U.S.A.
500W MAX 50/60 HZ ~
RIGHT INPUT
048
RISK OF ELECTRIC SHOCK
DO NOT OPEN
CAUTION
!
METER LIGHTS
OFF
ON
WARNING
RISK OF HAZARDOUS ENERGY!
MAKE PROPER SPEAKER CONNECTIONS
SEE OWNERS MANUAL
WARNING
RISK OF HAZARDOUS ENERGY!
MAKE PROPER SPEAKER CONNECTIONS
SEE OWNERS MANUAL
WARNING
TO PREVENT FIRE AND SHOCK HAZARD, DO NOT
EXPOSE THIS DEVICE TO RAIN OR MOISTURE.
UNIT MUST BE OPERATED IN A HORIZONTAL POSITION.
-DO NOT OPERATE WITH COVERS REMOVED-
UNIT CONTAINS VOLTAGES WHICH MAY BE HAZARDOUS.
CAUTION
FOR CONTINUED PROTECTION AGAINST
FIRE HAZARD REPLACE FUSE ONLY
WITH SAME TYPE AND RATING
Left and Right XLR inputs
Meter Lights on/o
12V remote trigger
Speaker connections
Fuse holder
A.C. Mains connector
Back Panel Controls and Connections

9
Connections
Input Connectors
The Reference 75 SE uses a fully balanced
circuit topology and has a pair of balanced
XLR input connectors on the rear panel. It
therefore requires a balanced preamplier
output, as provided by most Audio
Research preampliers. Connect your
preamplier’s output to the Reference
75 SE before turning on the amplier.
Output Connectors
Heavy-duty output terminals are provided
on the rear panel for 4 or 8-ohm speaker
impedance loads. Using high-quality
speaker cables, securely fasten the (-)
speaker lead to the appropriate (black)
terminal, then the (+) lead to the matching
(red) terminal. Follow your speaker
manufacturer’s impedance specication.
The Reference 75 SE puts out the
same amount of power whether the
4 or 8-ohm terminals are used.
Matching
It is important to use as close as possible an
impedance match between the amplier
and speaker for optimum transfer of
power to the speaker with minimum
distortion. In the case of speaker systems
with signicant variations in impedance
throughout the frequency spectrum,
such as most electrostatic types,
determine the best impedance match
empirically for best overall sonic results.
Connect the Reference 75 SE input
to the preamplier or electronic
crossover, using only the highest
grade of audio interconnect cables.
To avoid sonic degradation use the
shortest practical length of cables.
Important
Use the best available speaker wires
and interconnects. Audio Research
cannot emphasize this enough. As
better components and systems are
developed, it becomes increasingly
important to avoid the limitations of
inferior system interconnections.
It is important sonically that your entire
system be connected so that the audio
signal arriving at the speakers has
correct, or ‘absolute’ polarity (i.e., non-
inverted). Connect the black or ‘–‘ speaker
terminal to the wire that connects
to the ‘0’ terminal on the Reference
75 SE. Connect the red or ‘+’ speaker
terminal to the wire that connects to
the ‘4’ or ‘8’ terminal on the Reference
75 SE and tighten the speaker terminals
securely to ensure best sonic results.

10
Connections
Remote Turn-on
The Reference 75 SE has a built-in 12V DC
remote turn-on/o circuit for operation
by a master control system in a home
theater or large audio system. Use a
3.5mm (.140”) diameter mono mini
plug to connect to the +12V IN jack
on the rear of the Reference 75 SE.
The +12V IN jack should be connected to
the +12V DC output of the master control
system, using a continuous +12V DC
signal at 12mA per Reference 75 SE for the
duration of amplier on-time. Do not use
a momentary or data pulse control signal.
The +12V DC remote jacks have polarity
protection, so they will not operate if a
-12V DC signal is accidentally connected,
or if the control wires are reversed.
When the 12V DC remote turn-on/o
circuit is used, the power switch on the
front panel should be turned o.