Owner’s Manual
Model LS26
STEREO PREAMPLIFIER
3900 ANNAPOLIS LANE NORTH / PLYMOUTH, MINNESOTA 55447-5447 / PHONE: 763-577-9700 FAX: 763-577-0323
Model LS26
Model LS26
Section
Page No.
Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Installation of Vacuum Tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Description of Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1, 2, 3
Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Installation Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Operating Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Tape Recording Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Disposal and Recycling Guidelines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Limited Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Model LS26
DISPLAY
VACUUM TUBE PRE AM PLI FI ER
MOD EL LS2 6 HIGH DEFINITION
POWER
MONO
BAL/SE
PROC
MONITOR
®
MUTE
MODEL LS26
TUNER
PHONO
CD
VIDEO
AUX 1
AUX 2
MONITOR
PROCESSOR RECORD OUT
MAIN OUT 1
STEREO PREAMPLIFIER
MAIN OUT 2
RIGHT
PLYMOUTH, MINNESOTA
MADE IN U. S. A.
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.
SERIAL
+12V
OUT
VOLTS
CAUTION
FOR PROTECTION AGAINST FIRE HAZARD
REPLACE ONLY WITH SAME RATING FUSES.
3A SLO-BLO
T2A (230V)
LEFT
TUNER
PHONO
CD
VIDEO
AUX 1
AUX 2
MONITOR
PROCESSOR RECORD OUT
MAIN OUT 1
MAIN OUT 2
50 W MAX
50/ 60 HZ ˜
Model LS26
Adjusts illumination of display to
eight levels plus off.
DISPLAY
POWER
Turns power on/off.
CD
TUNER
VIDEO
Select one of six available audio inputs.
PHONO
AUX1
AUX2
Routes the monitor input signal to
the main outputs.
BAL L
MON
BAL R
Adjusts balance left. Bar graph
indicates balance in display window.
Mutes output of the LS26.
n l
VOL DN
Adjusts volume down. Visible as
numeric readout in display window.
Select as appropriate for Balanced (BAL)
or Single-Ended (SE) input for each source.
Inverts absolute phase of all outputs.
MUTE
VOL UP
BAL/SE
MONO
HOURS
INVERT
GAIN
PROC
MODEL LS26
PLYMOUTH MINNESOTA U.S.A.
Adjusts balance right. Bar graph
indicates balance in display window.
Adjusts volume up. Visible as numeric
readout in display window.
Sums L and R input for mono output
from any source selected.
Displays number of operating hours
vacuum tubes have been in service.
Input for external A–V processor. Provides
unity gain, disabling volume controls. NA
appears in display window.
Selects low, medium or high output gain
settings for each input source.
NOTE: All LS26 functions are available on the LS26R hand held
remote controller. All functions are
indicated in the display window as
they are selected. See “Description
of Controls” in this manual for more
information.
1
Model LS26
Preface
Warning!
Please take time to carefully read and understand the
following instructions before you install or attempt to operate your Audio Research LS26 preamplifier. Becoming
familiar with the product and its correct operating procedures will help assure you of maximum musical enjoyment
and reliable operation. The effort you invest now will be
well rewarded in the years ahead.
Do not attempt to install or replace vacuum tubes
unless this unit is first turned off and disconnected
from A.C. power outlet. Unit should be connected to
A.C. outlet and turned on only after all vacuum tubes
have been installed and appropriate panels
replaced and fastened. See owner's manual for
installation details.
Warnings
Before replacing vacuum tubes, turn off unit, disconnect from A.C. outlet and allow existing tubes to cool
before attempting to remove and replace with new
tubes. Hot tubes may cause burns or other injury if
not first allowed to cool.
1. To prevent fire or shock hazard, do not expose this
product to rain or moisture.
2. This unit operates on voltages which can cause serious
injury or death. Do not operate with covers removed.
Any necessary servicing should be carried out by your
authorized Audio Research dealer or other qualified
electronics technician.
3. The power cord supplied with this unit is safety-tested
and is equipped with a proper grounding plug. If used
normally, it will provide a safe earth ground connection
of the chassis. Defeat of the grounding plug or use
of a power cord without a grounding plug, or any
unauthorized modification of the active circuitry or
controls of this unit, automatically voids warranty
coverage, and could cause injury or death.
4. For safe operation and protection against fire hazard,
replace fuses only with those of the same type and
rating as those supplied with this unit.
When replacing tubes, do not touch other components, as the circuit may retain sufficient levels of
voltage and current to cause injury or death.
Co ntact Audio Resear ch Customer Service
(763-577-9700) if you have any questions about
installing or replacing vacuum tubes in this unit.
DO NOT ATTEMPT TO OPERATE THIS
EQUIPMENT BEFORE INSTALLING THE NUMBERED
VACUUM TUBES IN THEIR RESPECTIVE SOCKETS.
REAR
Packaging
Save all packaging accompanying this product. You have
purchased a precision electronic instrument, and it should
be properly cartoned any time shipment becomes necessary. It is very possible that this unit could be damaged
during shipment if repackaged in cartoning other than that
designed for it. The original packaging materials help protect your investment from unnecessary damage, delay and
added expense whenever shipment of this unit is required.
TUBE LOCATIONS
TOP VIEW
V2
V1
FRONT
Installation of Vacuum Tubes
Note: This unit has been shipped with the vacuum tubes
installed in a protective foam block under the top cover.
Using a phillips-head screwdriver to loosen the fastening
screws, remove the top cover and set aside. Remove the
tubes carefully from the protective foam block and store
the foam block with the carton.
Diagram indicates relative positions of two 6H30 tubes
located on circuit board as viewed from the front and looking
down from above the preamplifier.
Description of Controls
F ront Panel Rotary Contro l s
The LS26 has two microprocessor-driven rotary
controls.
The rotary control on the left adjusts Volume (output level)
up or down for both R and L channels. Volume control is
also selectable via Vol DN and Vol UP buttons on the
remote control. Volume adjustment is indicated in the
display window by numeric digits on 0 –103 scale.
1
Model LS26
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.
When engaged, “PROC” and “UNITY GAIN” will appear in
the display, and the volume control is not adjustable
because gain is fixed. The preamp will also mute the input
after “PROC” is engaged.
The rotary control on the right selects any of six input
sources connected to the preamp: CD, Video, Aux 1, Aux 2,
tuner and phono. Each of these sources may also be selected via direct access buttons on the remote control. The
selected source is indicated in the display window.
WARNING: Before unmuting the “PROC” input, be sure
to turn the volume down on the home-theater processor.
Never connect a source with a fixed level output (DVD
player, tuner, CD, etc.) to the PROC input or the
amplifier(s) and speaker system could be damaged when
the LS26 is unmuted.
F ront Panel and LS26R Remote
Control Buttons
POWER ON/OFF: Supplies power from A.C. wall outlet to
preamp; indicated by active display window. Function
also on remote control.
For approximately 50 seconds after start up, “Mute”
appears in the display window and flashes until the automatic muting cycle is completed. This also occurs in the
event of power interruption. Upon completing the cycle,
“Mute” will cease flashing. The preamp will remain muted
until normal operation is selected by pressing the “Mute”
button.
MUTE: When activated, electrically mutes all output of the
preamplifier; 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 amplifier and speakers from unexpected
signal pulses. When deactivated, “Mute” disappears from
the display window allowing normal operation. Function
also on remote control.
The LS26 also has automatic muting to help protect system
components during A.C. power interruptions or low line
voltage. When sensing these conditions, the preamp
automatically goes into “Mute” and disables all outputs.
The 50-second warm-up timer will restart and “Mute” will
flash in the display window when normal power conditions have been restored.
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, amplifier failure or speaker
malfunction.
PROCESSOR (PROC): May be selected by button on front
panel or on remote control. Selects external A-V (home
theater) processor as input source and controller of volume
level for R and L channels. LS26 provides Unity Gain when
this input is selected.
VOLUME UP/ DOWN: Increases/decreases overall volume
level of both channels equally for whichever input has been
selected. Caution: do not turn up volume beyond normal
listening levels when “Mute” is engaged to avoid unexpected or possibly damaging sound levels. It is a good idea to
reduce volume whenever changing program sources, even
when muted. Function available on remote control buttons
and front panel rotary control on left. .
B A L / S E: Select as appropriate for each input. For source
components having balanced (XLR) connections to the
LS26, select BAL. For single-ended (RCA) sources,
select SE. Once selected for an input source, the setting is
memorized.
MONO: Sums L and R input for mono output from any
source selected. Remembers setting for each input.
MONITOR (MON): Selecting MONITOR (“MONITOR”
appears on display) routes Monitor input signal to the Main
outputs.
The Input Selector indicates what is routed to the Record
out. To exit the monitor position and return to program
source controlled by input selector (CD, Tuner, Phono, etc.),
press monitor switch again.
Note: The gain of the LS26 through the monitor input is
not adjustable by gain selector button (on the remote), and
is fixed at “High” gain (the gain setting on the display is
unlit in the “Monitor” position).
LS26R Remote Control Only
DISPLAY: Selects one of nine display illumination levels,
including off. When off, the display can be reactivated for
10 seconds at a low level by pressing any button
(except Power) on remote or control on front panel.
BAL L / B AL R: Adjusts balance left or right. Adjustment
appears in display window as movable marker on bar
graph. Useful for compensating for uneven speaker placement or imbalanced output from a phono cartridge.
2
Model LS26
H O U R S : When pressed, displays number of operating
hours vacuum tubes have been in service. WARNING: after
replacing tubes, this function should be reset to “0” only by
a qualified technician. Hours display can be reset to “0” by
pressing black button labeled “Reset Hours” located on
lower right corner of circuit board directly behind display
window. The preamp must be “On” to reset function–the
service technician must be careful to avoid any contact with
other circuit components during reset operation. Contact
Audio Research customer service (763-577-9700) for information regarding this procedure.
It is possible to dub or copy from one recorder to another
by connecting the output of the source recorder to an
unused set of stereo inputs (Aux 1, Aux 2). The signal
will then be routed to the Record Out connectors when
that input source is selected.
GAIN: The Gain selector limits the input level to the LS26,
with resulting Low, Medium and High labeled gain option
settings to the outputs. Note that the gain to the single
ended outputs at each of the three settings is half of the
gain to the balanced outputs at the same setting. The gain
options allow limiting the output of “hot” high-gain signal
sources to the preamplifier's input circuitry and prevents
potential overloading. Properly used, this results in extremely wide signal input range capability while preserving
optimum use of the Volume control. For each input source,
simply set the Gain selector at the highest of the three gain
settings viewed on the display that allows you to use the
Volume control over the desired range without audible
distortion on peak levels from your program source. Once
you have selected the optimum gain setting for a given
input, the LS26 will “memorize” it and return to that gain
setting each time you select that input. Note that the Gain
selector defaults to the “High” setting for each input unless
another is selected.
While the LS26 does not dissipate an unusual amount of
heat, it is important that it be provided with
reasonable airflow to assure long, trouble-free operation.
In addition, the following installation guidelines will help
insure maximum sonic performance as well as reliable
service:
1. Operate unit in upright and horizontal position, preferably on solid, non-metal shelving.
2. Do not stack the preamp on top of a power amplifier: not
only could this cause overheating, but hum may be
introduced into the preamp from the proximity of the
amplifier's power transformer. Do not stack components
or other objects directly on top of the LS26.
3. Do not place or operate your preamp on a soft or
irregular surface such as a rug. This will prevent proper
ventilation.
4. Do not operate your preamp without the top and bottom
covers installed. These are required both for
safety as well as shielding from interference (except in
service operations by qualified personnel).
12V IN/OUT REMOTE START JACKS: The +12V DC input/output jacks provide the ability to remotely turn on and
off the preamp and other linked components such as power
amplifiers having similar capabilities.
Installation Instructions
I N V E R T : Inverts absolute phase of the output signal.
Remembers setting for each input.
Connections
INPUT CONNECTORS: The LS26 provides eight pairs of
BAL/SE input connectors: CD, Tuner, Phono, Video, Aux 1,
A ux 2, Monitor and Processor. The BAL/SE selector
button (front panel and on remote) should be selected
to match the type of connection used (BAL or SE) on each
input.
Connect either the BAL or SE connectors for each input.
Never connect the BAL and SE connectors simultaneously
for any input.
OUTPUT CONNECTORS: Two pairs of BAL / SE main
outputs are provided.
RECORD OUTPUT: The BAL/SE tape outputs should be
connected to your recorder's “Record” or “Line” inputs.
These outputs provide a fixed-level two-channel signal
(R, L ) to your recorder from whichever input is selected.
The non-variable output level will be the same as the output of the selected source.
3
Operating Procedure
Start-Up:
1. Secure all rear-panel connections between LS26, power
amplifier(s) and input sources.
2. Plug three-prong power cord from rear of chassis into
grounded AC wall outlet. The Power switch defaults to
“off” when the unit is plugged into a power receptacle.
3. Press power switch (either remote or front panel). “Mute”
will will flash in the display window for approximately
50 seconds, then cease flashing and remain in the
display. Press “Mute” to initiate operation.
4. Select input source, then BAL or SE as necessary.
Shut-Down:
1. Activate “Mute” function.
2. Set Volume level to “0”.
3. Turn off power amplifier(s).
4. Press Power switch to “off ”.
5. Turn off input sources.
Model LS26
Tape Recording Procedure
When using the LS26 as a control center for recording, the
program source to be recorded must be connected to one of
the six inputs controlled by the Input selector switch or to
the Processor input. This routes the selected program to the
Record output.
Note: If the Processor input is activated by selecting the
“Processor” switch position, all other inputs will be deactivated. When recording from the Processor input to the
Record out of the LS26, the level of the recording will be
dependent on the level setting of the processor.
If you own a three-head tape deck, and wish to monitor the
actual tape while making a recording (for a true “A-B” comparison of signals before and after recording), connect the
tape deck output to the Monitor input.
It is also possible to dub from one tape deck to another.
Simply connect the output from one tape deck to an unused set of inputs controlled by the Input selector (Tuner,
Phono, C D, etc.) on the LS26. This signal will then
be routed to the second tape deck through the Record
output when the appropriate input is selected on the Input
selector.
The vacuum tubes inside your LS26 are quality 6H30 dual
triode tubes and with normal use should not need to
be changed for approximately 4,000 hours of use. Replacement tubes should be of equivalent quality and are
available from Audio Research. Note that tube numbers
(V1 and V2) match printed numbers next to tube sockets
on circuit board.
Should service be necessary, please contact your
Audio Research dealer, or Audio Research Customer Service
at 763 577-9700.
Cleaning
To maintain the new appearance of this unit, 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 fingerprints or similar
smudges. Cleaners containing abrasives should not be used
as they will damage the anodized finish of the front panel.
A small, soft paint brush is effective in removing dust from
bevels, the recessed nameplate and other features of the
front panel.
Troubleshooting:
It is possible for a static discharge to temporarily disable
the microprocessor that allows the controls to function. If
this should occur, depress the “Mute” button, then turn
off the preamp and unplug the preamp from the A.C. receptacle for 60 seconds. Reconnect the A.C. plug and turn the
preamp back on, along with other components. The
controls should resume normal operation. If the problem
persists, contact your dealer or Audio Research Customer
Service at 763-577-9700.
Servicing
Because of its careful design and exacting standards
of manufacture, your LS26 should require no routine maintenance. The remote control's batteries (AAA) should be
replaced once a year.
CAUTION: Your LS26 contains sufficient levels of voltage
and current to be lethal. Do not tamper with a
component or part inside the unit. Refer any needed
service to your authorized Audio Research dealer or other
qualified technician.
Disposal and Recycling Guidelines
To dispose of this electronic product, do not place in landfill. 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 (763-5779700) for the name of your importing distributor and how
to contact them.
Packing and shipping materials may be disposed of in a
normal manner.
4
Model LS26
Limited Warranty
Specifications
Audio Research Corporation products are covered by a 3Year 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.
FREQUENCY RESPONSE: +0-3dB, 0.2Hz to 160kHz at
rated output (Balanced, 200k ohms load)
In the United States, the specific terms, conditions and
remedies for fulfillment 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 specific terms and remedies for fulfillment 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.
INPUT IMPEDANCE: 120K ohms Balanced, 60K ohms SE.
Inputs (8): Tuner, Phono, CD, Video, Aux 1, Aux 2, Monitor,
Processor (XLR and RCA connectors).
In the unlikely event that technical service beyond the ability of the importer is required, Audio Research will fulfill
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.
RATED OUTPUTS: 2V RMS 1Hz to 100kHz into 200K ohm
balanced load (maximum balanced output capability is 15V
RMS at less than 0.5% THD at 1kHz).
DISTORTION: Less than .01% at 2V RMS BAL output.
GAIN: Main output: Selectable for each input: 24dB, 18dB,
12dB Balanced output. (18dB, 12dB, 6dB SE output.)
Record output: 0dB (Processor input: 0dB balanced).
OUTPUT IMPEDANCE: 700 ohms Balanced, 350 ohms SE
Main (2), 20K ohms minimum load and 2000pF maximum
capacitance. Outputs (3): 2 Main, 1 Record (XLR and RCA
connectors).
OUTPUT POLARITY: Non-inverting.
MAXIMUM INPUT: Low Gain: 48V RMS BAL, 24V RMS SE,
Medium Gain: 24V RMS BAL, 12V RMS SE, High Gain: 12V
RMS BAL, 6V RMS SE.
CONTROLS: Rotary volume selector (104 steps) and
rotary input selector.
Push buttons: Power, Mono, BAL/SE, Proc, Monitor, Mute.
Also remote buttons: Display, Bal L, Bal R, Hours, Invert, Gain.
POWER SUPPLIES: Electronically-regulated low and high
voltage supplies. Automatic 50 sec. warm-up/brown-out mute.
Line regulation better than .01%.
NOISE: 1.3uV RMS residual IHF weighted balanced equivalent
input noise with volume at 1 (100dB below 2V RMS output).
TUBE COMPLEMENT: 2-6H30P dual triode, ( Hybrid
JFET/ tube audio circuit, solid-state power supply.)
POWER REQUIREMENTS: 105-130VAC 60Hz (210-260VAC
50/60Hz) 50 watts maximum.
DIMENSIONS: 19" (48 cm) W x 5.25" (13.4 cm) H (standard
rack panel) x 12" (30.5 cm) D. Handles extend 1.50"
(3.8 cm) forward of the front panel.
WEIGHT: 16.5 lbs. (7.5 kg) Net; 26 lbs. (11.8 kg) Shipping.
Specifications subject to change without notice.
©2006 Audio Research Corporation.
5
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