Audio Research GSi75 User manual
H I G H D E F I N I T I O N ®
GSi75
Stereo Integrated Amplier
User Guide
H I G H D E F I N I T I O N ®
Thank You.
Thank you for choosing the GSi75 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 integrated amplier. Once
installed, please allow an appropriate break-
in period to fully appreciate the benets
this amplier will provide to your system.
After reading the user guide, if you have any
further questions regarding your integrated
amplier, 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 GSi75
To Remove the Top Cover
In Your System
Connections
Back Panel Controls and Connections
Input Connectors
Output Connectors
IR Input
12 volt Trigger
RS-232 Control
Matching
A.C. Power Connection
5
6
6
7
9
9
9
9
9
9
9
10
Operation
Front Panel Controls and Displays
Start-Up
Shut-Down
Break-in
Front Panel Controls
Remote-only Controls
Settings Menu
Using the Headphone Output
Output Tube Bias
Using a Turntable
Using the Digital-to-Analog Converter
Windows Software Installation
Conguring the DAC for Windows
Conguring JRiver Media Center for Windows
Conguring the DAC for Mac OS
Conguring JRiver Media Center for Mac
Conguring Signalyst HQPlayer for Mac
12
13
13
13
14
15
17
20
21
22
23
24
26
28
29
30
30
Maintenance
Servicing
Cleaning
Disposal and Recycling Guidelines
Warranty
Specications
32
32
32
33
34
5
Warnings
To prevent re, or shock hazard, do not
expose your GSi75 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. Aside from the tube cover, do not operate
with covers removed. Refer servicing to your authorized
Audio Research dealer or other qualied personnel.
The detachable power cord on your GSi75 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 GSi75 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.
The GSi75 is shipped with a protective, ventilated
cover. While the cover may be removed, its
use is recommended to prevent accidental
contact with the hot vacuum tubes.
For continued protection against re hazard,
replace the fuse only with the same type and
rating as specied at the fuse holder.
The power button on the front of this unit, when
o, does not disconnect all power from this
unit. This unit is in sleep mode when not on.
This unit is RoHS compliant.
A note about packaging...
Save all packaging in a dry place away from re hazard.
Your GSi75 integrated amplier 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 GSi75 from unnecessary damage or delay.
6
Before operating the GSi75
This unit has been shipped with the vacuum tubes
installed in protective foam in separate boxes packed
inside the shipping carton. Included are two matched
pairs of KT150 power output tubes and two 6H30 tubes.
Remove the tubes carefully from the protective foam.
To remove the top cover
Use a phillips-head screwdriver to remove the fastening
screws from the front and back edges of the tube cover
(you do not need to remove any screws from the side
panels of the cover). Note that the screws between
the tube cover and transformer cover can be dicult
to reach; the included screwdriver will reach them as
well as provide a magnetic tip to remove the screws.
Once all of the screws have been removed, carefully
lift the cover away from the chassis making
sure not to scratch the other surfaces.
After removing the top cover and the vacuum tubes
packed in protective foam, see the accompanying
illustration for instructions on installing the tubes for
your GSi75 in their proper locations in the chassis. Note
that the numbers written on each tube correspond
to a ‘V’ number etched on the chassis next to each
tube socket. Insert each tube rmly, carefully aligning
the tube pins with the corresponding socket holes.
Installation
Note
Double damping rings are installed at the factory and
positioned on each 6H30 tube for maximum sonic
performance.
7
Installation
In your system
To insure normal component life and safe operation
this unit must be operated only in an upright
position. Adequate airow 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 amplier
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 amplier must be supported
on a surface specically 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 airow
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 aect your
warranty, as well as the service life of the unit.
It is normal for a vacuum tube power amplier 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 aected thereby, providing the
requirements outlined above are adhered to.
Do not stack components or other objects directly on top
of the GSi75.
8
Connections
Phono and
Analog Inputs
Digital
Inputs
Speaker
Terminals
(right channel)
Speaker
Terminals
(left channel)
A.C. Mains
Connector
Fuse
RS-232
Connector
IR
Input
Back Panel Connections
9
Connections
Input Connectors
The GSi75 provides four pairs of single-ended, analog input
connectors: SE1 - 3, and PHONO, and three digital input
connectors: USB, TOS, and RCA. Please note that input
SE3 can be selected as a unity gain ‘processor’ input; in
this case, SE3 should only be connected to a component
with a volume control (such as a home theater
processor). For further information about the SE3
processor mode, see the section ‘Processor’ on page 16.
Note
The phono stage of the GSi75 has two gain settings
of 45 and 62 dB; please keep this in mind when
selecting a phono cartridge to pair with your
preamplier. For further information about
connecting a turntable, please see page 22.
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 ‘0’ (black) terminal, then the
(+) lead to the ‘4’ or ‘8’ (red) terminal. Follow your
speaker manufacturer’s impedance specication to
determine if you should use the 4 - or 8 - Ohm tap.
The GSi75 puts out the same amount of power
whether the 4 or 8-ohm terminals are used.
RS-232 Connection
The RS-232 connection allows for remote control via
systems such as Creston or other automation systems.
IR Input
The IR input can be used to link the GSi75 to an IR repeater
system with a standard mono 1/8” connector.
Matching
It is important to use as close as possible an
impedance match between the amplier and speaker
for optimum transfer of power to the speaker
with minimum distortion. In the case of speaker
systems with signicant variations in impedance
throughout the frequency spectrum, such as most
electrostatic types, determine the best impedance
match empirically for best overall sonic results.
10
Connections
A.C. Power Connection
It is important that the GSi75 be connected via its
supplied 20 amp IEC 12-gauge power cord to a
secure, dedicated A.C. power receptacle. Never
connect to convenience power receptacles on other
equipment. Only use the power switch on the front
of the GSi75 for On/O control of the amplier.
The AC power source for the GSi75 amplier should
be capable of supplying 10 amperes for 100 or 120
volt units, or 5 amperes for 220 or 240 volt units.
For the very best performance on 100 or 120 volt
circuits, the GSi75 should be connected to its own
AC power circuit branch, protected by a 15 amp
breaker. The other audio equipment should be
connected to a dierent power circuit and breaker.
The GSi75 should be turned on after the other
components of your system. If the GSi75 is turned
on before other components, the amplier will
amplify any extraneous turn-on noises those
components might generate, which could potentially
damage the loudspeakers. Good operating practice
dictates that the amplier should be turned on
last, and turned o rst in an audio system.
The GSi75 uses a grounding system that does not require
a ground-lifter adapter plug on the A.C. power cord to
minimize hum. The power cord supplied with the GSi75
has a standard grounding plug to provide maximum
safety when properly connected to a grounded wall
receptacle. If there is any question regarding proper
grounding procedures in your installation, seek help
from a qualied technician. Caution should be taken
before using custom after-market power cords: they
must be at least 12-gauge and have a standard grounding
plug properly installed. These power cords are to be
used with caution, at the sole risk of the owner.
If other AC powered equipment is used with the GSi75
it may be necessary to use ‘ground lifter’ adapters
on the power plugs of that equipment to minimize
system hum. Generally, the lowest hum is achieved
when the only direct connection between audio
common ‘ground’ and true earth ground occurs in the
preamplier, through its grounded power cord. Other
equipment in the system should have some form of
isolation to prevent ground loops and associated hum.
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