Audio Research LS28SE User manual

H I G H D E F I N I T I O N®

LS28SE

There is only One Reference®

Thank You.

Thank you for choosing the

LS28SE to be a part of your high

performance music listening

system. Since 1970, Audio Research

has been creating some of the

world’s ﬁnest 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 phono preampliﬁer. Once

installed, please allow an appropriate

break-in period to fully appreciate

the beneﬁts this preampliﬁer

will provide to your system.

After reading the user guide, if

you have any further questions

regarding your phono preampliﬁer,

contact your dealer or Audio

Research customer service - they

will be happy to help you make the

most of your new component.

Happy Listening!

Contents

Warnings

Installation

Connections

Operation

Settings Menu

Maintenance

Warranty

Speciﬁcations

Before Operating the LS28SE

In Your System

A Note about Vacuum Tubes

Back Panel Connections

Input Connectors

Output Connectors

A.C. Power Connection

RS-232, IR Input, and 12v Trigger

Front Panel Controls and Display

Start Up

Shut Down

Break In

Front Panel Controls

Remote Only Functions

System Settings - Menu Tree

Settings Menu

Auto Shutdown

Processor Mode

Tube Hours

Display Brightness

Volume Reset

Input Naming

Vacuum Tubes

Service

Cleaning

Disposal and Recycling Guidelines

To prevent ﬁre, or shock hazard, do not

expose your LS28SE 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 qualiﬁed

personnel.

The detachable power cord on your

LS28SE 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 LS28SE 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 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.

For continued protection against ﬁre

hazard, replace the fuse only with the

same type and rating as speciﬁed at the

fuse holder

(see page 19 for fuse information).

This unit is RoHS compliant.

The LS28SE 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, ampliﬁer failure or

speaker malfunction.

A note about packaging...

Save all packaging in a dry place away

from ﬁre hazard. Your LS28SE preampliﬁer

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 LS28SE from

unnecessary damage or delay.

Warnings

Installation

Before operating the LS28SE

Your LS28SE preampliﬁer is shipped

with the vacuum tubes packed in a

separate foam-lined carton. These must

be unpacked and installed before you

attempt to operate the preampliﬁer.

Included are four 6H30

tubes for the analog stage. Proceed

according to the following instructions.

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 tube carton with other

packing materials for possible future use.

Refasten top cover on the preampliﬁer.

right

channel

left

channel

Vacuum Tube Placement

In your system

To ensure normal component life and safe

operation this unit must be operated only

in an upright position. Adequate airﬂow

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 preampliﬁer 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 preampliﬁer must

be supported on a surface speciﬁcally

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 airﬂow above

and to each side of the unit is provided.

Audio Research recommends a minimum

of 6-8 inches (15-20 cm) of clearance

above the LS28SE to maintain proper

ambient operating temperature.

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 preampliﬁer

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.

A Note about Vacuum Tubes

The vacuum tubes in your LS28SE have

been burned in, tested and electrically

matched to provide the best performance

and reliability of your preampliﬁer. That

said, vacuum tubes must be replaced

from time to time. The 6H30 tubes in the

LS28SE should have an expected life

of approximately 4,000 hours, while the

6550WE tube in the power supply should

have a life expectancy of approximately

2,000 hours. These life expectancies are

only approximate.

Connections

Record Outputs

Main Outputs

RS-232 connector

Control

connections

Fuse Holder

A.C. Mains connector

Single-ended InputsBalanced Inputs

Output Connectors

Two pairs of BAL/SE main outputs are

provided. The outputs are connected

in parallel. If using both outputs

simultaneously, the combined input

impedance of the ampliﬁer(s) being

driven by the LS28SE must be greater

than or equal to 20k Ohms.

Input Connectors

The LS28SE provides eight pairs of input

connectors; four balanced and four

singleended, labeled BAL 1-4 and SE 1-4.

Back Panel Connections

A.C. Power Connection

It is important that the LS28SE 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 LS28SE for On/O control of the

preampliﬁer, or the IR input, RS232 or

remote control.

RS-232 Input

The RS-232 input allows connection of a

control or automation system.

IR Input

The IR input allows a remote IR sensor or

repeater system to be connected to the

LS28SE for control purposes, utilizing a

standard mono 1/8” connector.

12V Trigger Out

The +12V DC trigger out jack provides

the ability to remotely turn on and o the

preampliﬁer and other linked components

such as power ampliﬁers having similar

capabilities.

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).

Operation

Input Select Vacuum Fluorescent

Display Volume

Enter

(used with Menu)

Mono/Stereo

Invert Phase

Mute

Power On/O

Front Panel Controls

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