Audio Research GSPre User manual

H I G H D E F I N I T I O N ®
GSPre
Stereo Preamplier
User Guide

Thank You.
Thank you for choosing the GSPre 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 preamplier. Once installed,
please allow an appropriate break-in
period to fully appreciate the benets this
preamplier will provide to your system.
After reading the user guide, if you have any
further questions regarding your preampli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
Operation
Front Panel Controls and Displays
Start-Up
Shut-Down
Break-in
Front Panel Controls
Remote Only Functions
Settings Menu
Auto Shutdown
Processor On/O
Tube Hours
10
11
11
11
12
13
15
16
16
17
Maintenance
Servicing
Cleaning
Disposal and Recycling
Guidelines
Warranty
Specications
18
18
18
19
20
5
6
7
8
9
9
9
9
9
9
Warnings
Installation
Before Operating the GSPre
In Your System
Connections
Back Panel Connections
Input Connectors
Output Connectors
A.C. Power Connection
RS-232 Control
IR Input
12V Trigger Jack

5
Warnings
To prevent re, or shock hazard, do not
expose your GSPre 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 GSPre 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 GSPre 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.
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.
The GSPre also has automatic muting to help protect
system components in the event of low line voltage.
When sensing low line voltage, the preamp displays ‘Low
Line’ and automatically goes into ‘Mute’. This condition
will persist until the line voltage returns to a safe
operating level; please note the unit will remain in ‘Mute’
even after ‘Low Line’ no longer appears.
Note that automatic muting is only designed to
protect against power line interruptions or severe
voltage drop. It will not mute in the event of
subsonic transmissions from a faulty input source,
amplier failure or speaker malfunction.
A note about packaging...
Save all packaging in a dry place away from re hazard.
Your GSPre preampli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 GSPre from unnecessary damage or delay.

6
Before operating the GSPre
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 6H30 tubes for the line stage, and one matched
pair of 6H30 tubes for the phono preamplier. Remove
the tubes carefully from the protective foam. Using
a phillips-head screwdriver to loosen the fastening
screws, remove the top cover and set aside.
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 GSPre 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
left channel right channel
phono stage

7
Installation
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 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.
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 preampli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.
Do not stack the preamplier on top of a power amplier:
not only could this cause overheating, but hum may be
introduced into the preamp from the proximity of the
amplier’s power transformer.
Do not stack components or other objects directly on top
of the GSPre.

8
Connections
Back Panel Connections
A.C. Power
Connector
IR Input
12V
Trigger
RS-232
Connector
Fuse
Holder
Inputs Main
Outputs

9
Connections
Input Connectors
The GSPre provides four pairs of single-ended input
connectors: SE1 - 3, and PHONO. 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. In addition, there are two pairs of balanced input
connectors: BAL1 and BAL2.
Note
The phono stage of the GSPre has a gain of 58 dB; please
keep this in mind when selecting a phono cartridge to pair
with your preamplier. Audio Research recommends a
phono cartridge within an output voltage range of 0.5 mV
to 2.5 mV.
Output Connectors
One pair of balanced and one pair of single-ended main
output connectors are provided.
A.C. Power Connection
It is important that the GSPre be connected via its
supplied 15 amp IEC 14-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 GSPre for On/O control of the preamplier,
or the IR input, RS232 or remote control.
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 GSPre to an IR repeater
system with a standard mono 1/8” connector.
12V Trigger Jack
The +12V DC output connector provides the ability to
remotely turn on and o other linked components such
as power ampliers having similar capabilities.

10
Operation
Input
Select
Volume
Control
Cartridge
Impedance
Front Panel Controls and Displays
Menu Button
Power
On/O
Function
Indicators
Function
Buttons
side panel
Headphone
Output

11
Operation
Start-Up
• Secure all rear-panel connections between GSPre,
power amplier(s) and input sources.
• Plug three-prong power cord from rear of chassis
into grounded A.C. wall outlet. The Power switch
defaults to ’o’ when the unit is plugged into a power
receptacle.
• Press power switch (either on the remote or front
panel). The preamplier will begin the warm-up
sequence, which lasts approximately 40 seconds,
during which ‘MUTE’ will ash on the display. After the
warm-up sequence is complete, the unit will be muted.
Depress the front panel ‘MUTE’ button or the Mute
button on the remote to initiate normal operation.
You may depress the Mute button prior to the unit
completing the warm-up cycle; ‘MUTE OFF’ will ash on
the display until the warm-up cycle is complete.
• Select input source and adjust the volume as necessary.
Shut-Down
• Activate ‘MUTE’ function.
• Turn o power amplier(s).
• Press Power switch to ‘o’.
• Turn o input sources.
Note
The GSPre should be turned on before the amplier
in your system. If the GSPre is turned on after the
amplier, it will amplify any extraneous turn-on
noises the preamplier or other source components
might generate, which could potentially damage
the loudspeakers. Good operating practice
dictates that the amplier should be turned on
last, and turned o rst in an audio system.
Break-in
All quality stereo equipment benets from a break-in
period; during this time, the various components, wiring
and solder connections change as electrical signals pass
through them. While your GSPre will sound fantastic
out of the box, it will only improve with continued use.
example of display after warm-up sequence is
complete.

12
Operation
Front Panel Controls
The GSPre has two microprocessor-driven rotary controls
and ve buttons (Power, Menu, Mono, Speaker O, and
Mute).
Left Rotary control (Input Select)
Select input by rotating the control to the left or right. The
screen displays the current input at the top right.
Right Rotary control (Volume)
Adjust volume (output level) up or down for both L
and R channels. Volume control is also selectable via
VOL UP and VOL DN buttons on the remote control.
Volume adjustment is indicated in the display window by
numeric digits on 0–103 scale.
Do not turn volume up beyond normal listening levels
when ‘mute’ is engaged to avoid unexpected or possibly
damaging sound levels. Reduce volume level whenever
changing input sources, even when muted.
Power On/O
Supplies power from A.C. wall outlet to preamp;
indicated by active display window. The GSPre requires
approximately 40 seconds to warm up; this time is
required to stabilize the vacuum tubes. See ‘Start-Up
Procedure’ on page 11 for details.
Menu
The menu button enters the setup menu of the GSPre to
allow customizing certain settings of the preamplier.
See page 15 for further details about using the setup
menu.
Mono
Toggle between Stereo and Mono output.
Speaker O
Toggle between the main outputs on the rear panel and
the headphone jack, located on the right side of the unit.
Please note that the GSPre maintains individual volume
settings for the main and headphone outputs.
Mute
When activated, Mute electrically disables all output of
the preamplier; indicated by ‘MUTE’ in display window.
This control should be activated before switching inputs,
changing connections or shutting down your audio
system to help protect your amplier and speakers from
unexpected signal pulses. When deactivated, ‘MUTE’
disappears from the display window allowing normal
operation.

13
Operation
Invert
The invert button will change the polarity of the
output signal. This is useful for recordings that
may have been recorded with inverted phase.
Impedance
The impedance button allows you to change the input
impedance associated with the ‘Phono’ input; this
feature only operates when the ‘Phono’ input is selected.
To match the impedance of the GSPre with your
cartridge, refer to the specications included
with your phono cartridge. If no impedance
is indicated, contact the manufacturer.
If your cartridge impedance is dierent from the ve
settings oered on the GSPre, select the number
which is closest to that of your cartridge.
Note
Because it oers an additional gain stage, the Phono
input should only be used with a turntable. Connecting
another source, such as a CD player or TV to this
input, may cause signicant distortion which can
cause serious damage to your amplier or speakers.
Remote Only Functions
In addition to the controls found on the front
panel, the remote control oers access to the
following additional features of the GSPre.
Display Brightness Adjustment
The front panel display has six brightness settings, as
well as the ability to dim the display completely. To
change the brightness, use the ‘DSP UP’ or ‘DSP DN’
buttons on the remote. Note that when the display
is completely dimmed, a small square appears in the
middle of the display to indicate the unit is powered on.
Hours
Pressing the ‘HOURS’ button will display the total
accumulated hours of operation for the GSPre. This
is useful to determine the approximate number
of hours the vacuum tubes have been in use.
After ve seconds, the display will revert to the
normal operation screen. After replacing vacuum
tubes, the hours counter should be reset (see
instructions under ‘Settings Menu’ on page 17).
Note
The installed 6H30 vacuum tubes have an average
life span of approximately 4,000 hours. After this
time, we recommend replacing them to maintain
the best performance of your preamplier.

14
Operation
Balance
The Balance control adjusts the output from center
position to the left or right channels, which in
turn will shift the center point of the sonic image.
This is useful in the event the main listening
position is not centered between the speakers,
or can help with certain room anomalies.
To adjust the balance, press the ‘BAL L’ or ‘BAL
R’ button on the remote. The balance scale will
appear at the bottom the display, and the indicator
block will move in the selected direction:
After ve seconds of inactivity, the balance scale
will disappear from the screen. If the balance
has been shifted to the right or left, ‘R+’ or
‘L+’ will appear at the bottom left corner.
Balance scale in center position
Balance scale shifted right

15
Operation
Settings Menu
The GSPre has been designed with a simple, intuitive
menu to allow you adjustment of several features of
the preamplier. To enter the menu, press the ‘MENU’
button on the remote or front panel. If no further
interaction with the preamplier or remote is taken
for ve seconds, the GSPre reverts back to its normal
operation screen. Continuing to press the ‘Menu’ button
will toggle you through the dierent setting options:
While a menu item is displayed, rotating the volume
knob on the front panel, or using the volume up/down
buttons on the remote, will adjust the settings of
that particular selecton. After making the appropriate
change, pressing the ‘MUTE’ button will conrm the new
setting, and the display will show ‘OKAY’ for ve seconds
before reverting back to the normal operation screen.
For example:
Press ‘MENU’ until desired menu item is
displayed
Turn volume knob or use volume up/down
buttons on remote to make change
Press ‘MUTE’ button to conrm change
After ve seconds, display reverts to normal
operation screen
Pressing the ‘Menu’ button will enter the GSPre
into the Settings Menu. Pressing repeatedly will
toggle through the menu options.

16
Settings Menu continued...
Auto Shutdown
The GSPre is equipped with an auto shut o
feature, designed to turn the preamplier o
after a period of time during which it is not used.
The auto shut o feature senses any interaction
with the preamplier, such as button presses,
changing the volume, remote usage, etc.
To change/disengage the auto shutdown feature, press
the ‘MENU’ button until the ‘AUTO SHUTDOWN’
screen is displayed. Using the volume knob on the front
panel, or the volume up/down buttons on the remote,
you have the option for ‘o’ (no auto shutdown) or
1-8 hours. Once you have made a selection, press
‘MUTE’ to conrm. The display will show ‘OKAY’ before
reverting back to the normal operation screen.
Note
The auto shutdown feature is not in the
signal path of the preamplier and has no
deleterious sonic eect to music playback.
Processor On/O
The SE3 input of the GSPre can be selected as a standard,
volume-controlled input like the other inputs, or it
can be set as a ‘unity gain’ processor input. This is
useful when combining the GSPre with a multichannel
surround sound processor to maintain the same
speaker/amplier system for left and right channels.
To use SE3 as a processor input, connect the left and
right output channels from your surround sound
processor to the left and right SE3 inputs. Press the
‘MENU’ button until ‘PROCESSOR’ is displayed:
Turn the front panel volume knob, or press the
volume up/down buttons on the remote to
change the setting to ‘PROCESSOR ON’:

17
Conrm the setting by pressing the ‘MUTE’ button,
and the display will show ‘OKAY’ before reverting
back to the normal operation screen. Now when
SE3 is selected, it will display ‘PROCESSOR’ and
the volume control will be disengaged:
Tube Hours
The tube hours display shows the accumulated time
the GSPre has been powered on. This is useful for
determining the number of usage hours of the
installed vacuum tubes. After approximately 4,000
hours, the vacuum tubes should be replaced and
the tube hours counter should be reset to zero.
To reset the tube hours counter, press the ‘MENU’
button until ‘TUBE HOURS’ is shown.
Turn the front panel volume knob, or press the
volume up/down buttons on the remote until
the display reads ‘TUBE HOURS RESET’:
Press the ‘MUTE’ button to conrm, and
the display will read ‘CONFIRM?’:
Then press ‘MUTE’ a second time to reset the counter.
The display will show ‘OKAY’ for ve seconds before
returning to the normal operation screen.
Note
Once the hour counter has been reset, the total
accumulated hours can not be recalled.

18
Servicing
Because of its careful design and exacting standards
of manufacture, your GSPre preamplier
should normally require only minimal service
to maintain its high level of performance.
Caution
Your GSPre preamplier contains sucient levels of
voltage and current to be lethal. Do not tamper with a
component or part inside the unit. Even with the power
turned o, a charge remains in the energy storage
capacitors for some time. Refer any needed service to
your authorized Audio Research dealer or other
qualied technician. Additional questions regarding
the operation, maintenance or servicing of your
preamplier, please contact the Customer Support
Department of Audio Research Corporation at
[email protected] or call 763-577-9700.
You may also initiate a service request by
visiting the Audio Research website (www.
audioresearch.com) and selecting ‘Service
Repair’ at the top right of the home page.
Cleaning
To maintain the new appearance of this preamplier,
occasionally wipe the front panel and top cover
with a soft, damp (not wet) cloth to remove
dust. A mild, non-alkaline soap solution may be
used to remove ngerprints or similar smudges.
Cleaners containing abrasives should not be used
as they will damage the anodized nish of the
front panel. A small, soft paintbrush is eective
in removing dust from bevels, the recessed
nameplate and other features of the front panel.
Disposal and Recycling Guidelines
To dispose of this electronic product, do not place
in landll. In accordance with the European Union
Waste Electrical and Electronic Equipment (WEEE)
directive eective August 2005, this product may
contain regulated materials which upon disposal
require special reuse and recycling processing.
Please contact your dealer or importing distributor
for instructions on proper disposal of this product in
your country. Or, contact Audio Research Corporation
(763.577.9700) for the name of your importing distributor
and how to contact them. Packing and shipping
materials may be disposed of in a normal manner.
Maintenance

19
Warranty
Audio Research Corporation products are covered by a
3-Year Limited Warranty or a 90-Day Limited Warranty
(vacuum tubes). This Limited Warranty initiates from
the date of purchase, and is limited to the original
purchaser, or in the case of demonstration equipment,
limited to the balance of warranty remaining after
original shipment to the retailer or importer.
In the United States, the specic terms, conditions
and remedies for fulllment of this Limited Warranty
are listed on the warranty card accompanying the
product in its shipping carton. The warranty terms are
also available on the internet at www.audioresearch.
com/en-us/company/warranty-statement. Outside
the United States, the authorized importing retailer
or distributor has accepted the responsibility for
warranty of Audio Research products sold by them.
The specic terms and remedies for fulllment of
the Limited Warranty may vary from country to
country. Warranty service should normally be
obtained from the importing retailer or distributor
from whom the product was purchased.
In the unlikely event that technical service beyond the
ability of the importer is required, Audio Research
will fulll the terms and conditions of the Limited
Warranty. Such product must be returned at the
purchaser’s expense to the Audio Research factory,
along with a photocopy of the dated purchase
receipt for the product, a written description of
the problem(s) encountered, and any information
necessary for return shipment. The cost of return
shipment is the responsibility of the purchaser.

20
Specications
Frequency Response:
Line: ±0.3dB 2Hz to 80kHz; : -3dB 0.8Hz to 220kHz
Phono: ±0.1dB of RIAA 10Hz to 20kHz, ±0.4dB 5Hz to 80kHz
Headphone: ±0.05dB 20Hz to 20kHz; : -3dB 0.8Hz to 220kHz
THD+N @ 1kHz:
Line: <0.002% at 2V RMS, Bal output
Phono: <0.005% at 3V RMS output, to Record output
Headphone: <0.009% at 1V RMS output
Gain @ 1kHz:
Line: 13.8 dB, Processor: 0dB
Phono: 58dB @ 1kHz to Record output
Headphone: 11.3dB
Noise (A-weighted):
Line: <-101dBV volume at max.
Phono: <-77dBV to Record output
Headphone: <-88dBV volume at max.
Channel Separation @ 1kHz:
Line: > 75dB Balanced output
Phono: >70dB to Record output
Headphone: >60dB
Signal to Noise Ratio @ 1kHz, A-weighted:
Line: >125dB Balanced output
Phono: >94dB to Record output
Headphone: >110dB
Input Impedance: 150kΩ Balanced, 75kΩ SE; Phono impedance
programmable (100, 200, 500, 1000 or 47kΩ w/200pF unbalanced)
Output Impedance @ 1kHz: 500Ω Balanced,
250Ω SE; <0.05Ω Headphone SE.
Maximum Input:
Line: 12V RMS Balanced, 6.0V RMS SE.
Phono: 11mV RMS at 1KHz.
Rated Output:
Line: 2V RMS (1V RMS SE) into 200kΩ balanced
load (maximum balanced output capability is 15V
RMS at less than 0.5% THD+N at 1KHz.)
Phono: 0.5V RMS into 200k load, Max output same as Line stage.
Headphone: 6V RMS maximum into 30Ω to 300Ω load.
Controls:
Volume, Input Selector. 5 Push Buttons: Power,
Mute, SPKR O, Mono, Menu. Rear: RS-232 control,
Remote IR input & Remote Trigger out.
Power Supplies: Electronically regulated low and high
voltage supplies. Automatic 45 sec. warm-up & brown-
out mute. Line regulation better than .01%.
Tube Complement: (6) 6H30P dual triodes.
Power Requirements: 100-125VAC 60HZ (200-250VAC
50/60Hz) 105 Watts. Standby: 1.5 Watts.
Dimensions:
width 19” (483 mm)
height 7 ¾” (197 mm)
depth 17 ¼” (438 mm)
Weight: 25 lbs. (11.3 kg)