Audio Research VSi75 User manual

VSi75
Integrated Amplifier
H I G H D E F I N I T I O N ®
User Guide

2Contents
Preface 3
Illustrations 4
Warnings 5
Installation
Vacuum Tubes 6
In your System 7
Connections
Rear Panel Connections 8
AC Power Connection 9
Operation
Power-up Procedure 10
General Notes about Usage 11
Resetting Controls 11
Automatic Mute Function 12
Front Panel Control Functions 13
Remote Control Functions 14
Maintenance
Adjusting Vacuum Tube Bias 15
Servicing 16
Cleaning 16
Disposal and Recycling Guidelines 16
Limited Warranty 17
Specications 18

3
Preface
Thank you for selecting the VSi75 as part of your music
listening system. The engineers and designers at Audio
Research have spent countless hours of listening and
testing to create an Integrated Amplier of the highest
caliber for music reproduction. The VSi75 has been
designed to provide you many years of playback.
Please take a few minutes to read through this guide
to help you better understand and optimize your new
integrated amplier. If you have any questions regarding
the operational functions, contact your dealer or
distributor for assistance.
Sit back and enjoy your new integrated amplier and the
enhancements it will bring to your system. The VSi75
will bring new life to your entire music collection.
Happy listening!

4Illustrations
POWER MUTE VOL DN VOL UP BIAS INPUT
CAUTION
FOR PROTECTION
AGAINST FIRE HAZARD
REPLACE FUSE ONLY WITH
SAME TYPE AND RATING
5A FUSE
SLO-BLO T4A (230V)
VSi75
INTEGRATED AMPLIFIER
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.
VOLTS
SERIAL
0
4
8
WARNING
RISK OF HAZARDOUS ENERGY!
MAKE PROPER SPEAKER CONNECTIONS
SEE OWNERS MANUAL.
PLYMOUTH, MINNESOTA
MADE IN U.S.A.
500W MAX 50/60 HZ
~
0
4
8
RISK OF ELECTRIC SHOCK
DO NOT OPEN
CAUTION
!
R
L
1
2
3
4
5
TAPE
OUT
WARNING
RISK OF HAZARDOUS ENERGY!
MAKE PROPER SPEAKER CONNECTIONS
SEE OWNERS MANUAL.
Front Panel
Rear Panel
BIAS
VSi75
1
DSP DN
DSP UP
MONO
2
3
4
5
POWER
VOL DN
VOL UP
MUTE
HOURS
H I G H D E F I N I T I O N ®
Remote

5
Warnings
Do not touch hot tubes. Keep away from children.
To prevent re, or shock hazard, do not expose your VSi75 to rain or
moisture.
This unit contains voltages which can cause serious injury or death. Do not
operate with top plate removed. Refer servicing to your authorized Audio
Research dealer or other qualied personnel.
The detachable power cord on your VSi75 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 VSi75 chassis to provide absolute protection
from electrical shock.
For continued protection against re hazard, replace the fuse only with the
same type and rating as specied at the fuse holder.
The appliance coupler at the rear of this unit must be accessible for
emergency power disconnect.
A note about packaging...
Save all packaging in a dry place away from re hazard. Your VSi75 Integrated
Amplier is a precision electronic instrument and should be properly cartoned
any time shipment is made. Because of its weight, it is highly probable that
the unit will be damaged during shipment if repackaged in cartoning other
than that designed for the unit. 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
VSi75 from unnecessary damage or delay.

6Installation
Vacuum Tubes
Before you operate the VSi75
Your VSi75 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 KT120 output tubes,
and two 6H30 dual triodes used in the input stage. Proceed according to
the following instructions.
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.
If you are using the optional tube cover, be sure the VSi75 is rst turned off.
Remove the top cover screws, and install the cover on top of the top plate.
Insert and retighten screws.
Note: double damping rings are installed at the factory on each 6H30 tube
for maximum sonic performance.
V5 V6
V2 V3V1 V4

7
Installation
In your System
To insure normal component life and safe operation this unit must be
operated only in a horizontal (upright) position. Adequate airow and proper
cooling thereby can occur only if there is no restriction below, behind and
above the unit.
The four special non-marring elastomer feet provide adequate spacing only
from a smooth, hard surface. Never operate the unit while it is sitting on a
surface such as a rug or carpet.
If the unit is to be operated in an enclosed equipment cabinet, an exhaust
fan is desirable so as not to operate the VSi75 in overheated ambient air.
The “ambient” operating temperature should never exceed 120° F or 49°
C. Improper installation will cause premature tube failure and will affect 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
affected thereby, providing the requirements outlined above are adhered to.

8Connections
Rear Panel Connections
All ve sets of Single-Ended inputs are clearly marked to indicate use.
6-Output binding posts (+) and (-), L & R, for 4 or 8 ohm speaker connection
1 - Power line cord inlet
1 - Power line fuseholder
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.
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 VSi75. Connect the red or”+” speaker
terminal to the wire that connects to the “4” or “8” terminal on the VSi75,
and tighten the speaker terminals securely to ensure best sonic results.
About cables:
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.
Connect the VSi75 input to the source components using only the highest
grade of audio interconnect cables. To avoid sonic degradation use the
shortest practical length of cables.

9
Connections
AC Power Connection
It is essential that the amplier be connected to a wall AC power receptacle,
or a similar heavy-duty source. If it is connected to convenience receptacles
on preampliers, etc., the full sonic capabilities of both the VSi75 and the
preamplier will be compromised.
For the very best sonic performance, the VSi75 should be connected to its
own AC power circuit branch, protected by a 15 or 20 amp breaker. The
other audio equipment should be connected to a different power circuit
and breaker. Avoid the use of extension cords. If they must be used on a
temporary basis, use 14-gauge or heavier cords.
The VSi75 utilizes a compatible grounding system that generally does not
require a “ground lifter” adapter plug on the AC power cord to minimize hum.
The 14-gauge power cord supplied with the VSi75 has a standard three-
prong grounding plug to provide maximum safety when it is connected to
a grounded wall receptacle. If there is any question regarding the safety
of grounding procedures, be certain to seek competent help with the
installation.
If electronic crossovers or other AC powered equipment are used with the
VSi75 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 preamplier, through its
grounded power cord. Other equipment in the system should have some
form of isolation to prevent ground loops and associated hum.

10 Operation
Power-up Procedure
Make sure you have read and complied with the Installation and Connection
instructions prior to attempting operation.
Press the “Power” switch. The Audio Research logo will appear for a few
seconds, then “Mute” will ash and a numeric countdown will show on the
LCD display while power supply stabilizes, indicating operation of automatic
muting circuit. After this automatic muting period the LCD display will show
the normal operating screen, and “Mute” will no longer be ashing. Adjust
the Volume control to the minimum level as indicated by the front panel LCD
display. When the “Mute” button is pressed, “Operate” will show on the
LCD display, indicating the VSi75 is ready for operation.
Note: If the LCD display does not illuminate after pressing the power
button, check the appropriate fuse for failure. An extra fuse for A.C. power
is included with your VSi75.
Press Input selector for desired source; set remaining switch options to
desired positions.
Activate selected input source, then deactivate Mute switch and adjust
Volume control as necessary.
Your VSi75 should now operate satisfactorily. However, a full stabilization or
warm-up time of approximately one hour is recommended for best sonic
performance.
Shut-Down
Set Mute switch to “Mute” position.
Adjust Volume control to minimum setting.
Press the “Power” button to shut unit off.

11
Operation
General Notes about Usage
If you turn off the VSi75 wait at least ve minutes before turning it on again.
This brief cool down period will reduce stress on the output tubes and
potential damage to them.
Audio Research does not recommend leaving your VSi75 on 24 hours a day
as is the custom of some listeners to achieve maximum sonic performance
on demand. While this is often recommended for solid-state equipment,
Audio Research does not recommend this procedure for vacuum tube
power ampliers. (2,000 hours of tube life will pass by in 84 days!)
CAUTION: Do not turn up the Volume control beyond normal listening
levels when the VSi75 is in the “mute” position. Always turn the Volume
control down when changing program sources, even when it is muted.
Resetting Controls
To avoid discharging static to the VSi75 controls, contact another surface
(such as a metal equipment rack) to drain away the charge before touching
the VSi75. If a static charge should “lock up” the microprocessor making the
front panel controls inoperable, unplug the VSi75 from its power receptacle.
After waiting two minutes, plug in the VSi75 and power it up with the rest
of the system; the controls should resume normal operation. If the problem
persists, contact your dealer or Audio Research Customer Service at 763-
577-9700.

12 Operation
Automatic Mute Function
The VSi75 has several provisions to help protect against misuse of the
exceptional dynamic range and wide band width that it offers. It is not
subject to damage itself, but some speakers are more limited in their
ability to with stand signal extremes. These provisions, both manual and
automatic, are designed not to interfere with the listening experience,
while giving reasonable protection against warm-up surges and power line
interruptions. However, for absolute protection of associated equipment,
some operator understanding and responsibility are required.
Initial “settling” time of all circuit parameters within the VSi75 requires
approximately 5 to 10 minutes. The automatic muting circuitry timer is
adjusted for about 40 seconds. (This is because recurrent interruption
“settling” time is much less. You would not want to wait for 5 to 10 minutes
each time such an interruption occurred.)
The Mute button allows manual disabling of the VSi75 inputs during the
switching of equipment. Use of this switch will minimize stress on your
VSi75 and other components. It is also highly recommended that manual
muting be employed during turn-off for maximum protection. The automatic
muting operates as follows:
1. The automatic muting always disables all inputs and overrides any manual
settings. (The “Operate” position of the manual Mute function is operational
only when the unit is not in the automatic mute mode.) Note: Power supply
regulation of the VSi75 is effective down to 100VAC (120V units) without
serious sonic degradation.
2. The automatic muting of the VSi75 is designed to be effective only against
power line interruptions and power line failures. It will not mute against
subsonic signal transmissions from your input source. Proper fusing of
speakers is essential to protect against excessive audio signal levels.

13
Operation
Front Panel Control Functions
VOLUME CONTROL: Pressing the down or up button decreases or
increases the volume level. Note that the VSi75 has 103 individual steps
across the volume control adjustment range. The corresponding level is
indicated on the LCD display.
INPUT: Allows selection of any of ve single-ended input sources 1, 2, 3,
4, and 5. Pressing the Input selector button steps through each input as
indicated on the LCD display.
POWER: Toggles power on and off from AC wall outlet to VSi75.
MUTE: Mute should always be activated between listening uses or before
switching inputs, in addition to turning the Volume control down. These
two simple precautions will prevent inadvertent misuse of your VSi75 and
help protect the amplier and speakers from unexpected transient signal
pulses. In “operate” position (indicated on the LCD display), the signal
passes normally to the outputs.
BIAS: Puts the VSi75 into bias mode for adjusting vacuum tube bias (see
page 15 for further details on adjusting bias).

14 Operation
Remote Control Functions
In addition to the functions on the front panel, the handheld remote also
offers the following functions:
MONO: Toggles the VSi75 between Stereo and Mono mode. “STEREO”
or “MONO” are displayed in the bottom right of the LCD display, indicating
mode.
1-5: Provides direct access to any of the ve single-ended inputs on the
VSi75.
DISP UP/DISP DOWN: Adjust the brightness of the backlighting on the
LCD display. Fifteen levels of illumination plus off are available. When off
is selected, the display will illuminate for ve seconds, after which there will
be only a green dot in the middle of the screen. Pressing any button on the
front panel or remote will reactivate the screen for another ve seconds.
HOURS: Toggles between main display screen and vacuum tube hours
meter. The hours meter can be reset to 0 after replacing the vacuum tubes;
to do so, remove the four screws on the top panel, and take the panel off.
At the front left of the circuit board, there is a small black “RESET” switch.
Press and hold this switch to reset the meter.

15
Maintenance
Adjusting Vacuum Tube Bias
As shipped from the factory, the output “bias” adjustments are set for a
nominal 65mA per KT120 tube. Under these idle conditions the tubes are
each dissipating a conservative amount of power of their total capacity.
This point of operation provides “enriched” Class AB 1, and will satisfy the
most critical listener.
For best results, operate and adjust the VSi75 at 120V AC. Adjustment
must be made under zero-signal conditions after at least 15-20 minutes of
uninterrupted stabilization time.
Pressing the “BIAS” button on the remote or front panel enters the VSi75 into
bias mode, beginning with tube V1. Using the included plastic alignment
tool, adjust the bias via the labeled adjustment port located in front of each
tube which corresponds with the “V” number shown on the LCD display
until the bias reads 65mA. Pressing the “BIAS” button again will advance
the unit to V2, V3, V4 and back to the main operation screen.

16 Maintenance
Servicing
CAUTION: Your VSi75 contains sufcient levels of voltage and current to
be lethal. Do not tamper with a component or parts inside the unit. Refer
any needed service to your authorized Audio Research dealer or other
qualied technician. Should service be necessary, please contact your
Audio Research dealer, or Audio Research Customer Service (763) 577-
9700.
Cleaning
To maintain the visual appearance of your VSi75, occasionally wipe the front
panel and top cover surfaces 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 brushed grain of the front panel nish, as well as the
LED display window. A dry 2-inch pure bristle paint brush works well to
remove dust from bevels, reliefs and switches.
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 effective 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.

17
Limited Warranty
Audio Research Corporation products are covered by a 3-Year Limited
Warranty, or a 90-Day Limited Warranty on 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, or may be obtained from the authorized retailer
or from the Audio Research Customer Service Department. 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.

18 Specications
Power Output: 75 watts per channel continuous from 20Hz to 20kHz. 1 kHz total harmonic distortion typically 1.5% at 75
watts, .05% at 1 watt.
Approximate actual power available at “clipping” 80 watts (1kHz). (Note that actual power output is dependent upon both line
voltage and “condition” i.e.: if power line has high distortion, maximum power will be affected adversely, although from a listening
standpoint this is not very critical.)
Power Bandwidth: (-3dB points) 12Hz to 70kHz.
Frequency Response: (-3dB points at 1 watt) 1.0Hz to 70 kHz.
Input Sensitivity: 0.55V RMS Single-ended for rated output. (32.5dB gain into 8 ohms.)
Input Impedance: 52.5K ohms Single-ended.
Inputs (5): 1, 2, 3, 4, 5 (Single Ended RCA connectors).
Maximum Input: 10V RMS (any input).
Output Polarity: Non-Inverting (any input).
Push Buttons: Volume up, Volume down (103 steps), Power, Input, Mute, Bias. All functions on IR remote control.
Output Taps: 8 ohms, 4 ohms.
Output Regulation: Approximately 2dB 8 ohm load to open circuit (Damping factor approximately 4).
Overall Negative Feedback: 4dB.
Slew Rate: 10 volts/microsecond.
Rise Time: 4 microseconds.
Hum & Noise: Less than 1.0 mV RMS -88dB below rated output (IHF weighted, Vol down).
Power Supplies: Electronically regulated Low and High voltage supplies for input stages. Automatic 40 sec. warm-up/brown-
out mute.
Power Supply Energy Storage: Approximately 350 joules.
Power Requirements: 100-125VAC 60Hz (200-250VAC 50Hz) 400 watts at rated output, 600 watts maximum, 210 watts at
“idle’: 1.0 watt power off.
Tubes Required: 2-Matched pair KT120-Power Output; 2 -6H30 driver.
Dimensions: Width 14.5” (36.8 cm)
Height 9.25” (23.5 cm)
Depth 16.25” (41.3 cm)
Rear connectors extend .88” beyond chassis.
Weight: 36.4 lbs. (16.5 kg) Net; 49.3 lbs. (22.4 kg) Shipping.
This unit is RoHS compliant
Specications subject to change without notice.
©2013 Audio Research Corporation.
H I G H D E F I N I T I O N ®