Audio Research Reference 250 SE User manual

Reference 250 SE

H I G H D E F I N I T I O N ®

Thank You.

Thank you for choosing the

Reference 250 SE 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

amplier. Once installed, please

allow an appropriate break-

in period to fully appreciate

the benets this amplier will

provide to your system.

After reading the user guide, if

you have any further questions

regarding your ampli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!

Contents

Warnings

Installation

Before Operating the Reference 250 SE

In Your System

Connections

Back Panel Controls and Connections

Input Connectors

Output Connectors

Matching

Remote Turn-on

A.C. Power Connection

Operation

Front Panel Controls and Displays

Start-Up

Shut-Down

Display Brightness Adjustment

Fan

Meter

Break-in

Output Tube Bias Adjust

Maintenance

Vacuum Tubes

Service

Cleaning

Disposal and Recycling Guidelines

Warranty

Specications

Warnings

To prevent re, or shock hazard,

do not expose your Reference

250 SE 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

Reference 250 SE 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 Reference 250 SE 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.

A note about packaging...

Save all packaging in a dry place away from

re hazard. Your Reference 250 SE

ampli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 Reference 250 SE

from unnecessary damage or delay.

Before operating the Reference 250 SE

Your Reference 250 SE 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 a matched

sextet of KT150 output tubes, a matched

pair of KT150 driver tubes, 2 6H30 dual

triode used in the input and regulator

stages, and a 6550WE for the power

supply regulator. Proceed according

to the following instructions.

Installation

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 foam blocks with other packing

materials for possible future use.

Refasten top cover on amplier.

V1 V2

V3 V4

V11

FRONT

REAR

TUBE LOCATIONS

TOP VIEW

V5 V6

V7 V8

V10

output

tubes

driver

tubes

power

supply

tubes

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 are no restrictions above and

behind the unit and on either side. Be sure

that airow to the 12V D. C. cooling fan

located on the rear panel is not blocked.

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 ampli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 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 aected

thereby, providing the requirements

outlined above are adhered to.

Installation

Connections

7A FUSE

SLO-BLO

T4A (230V) IN OUT

+12V REMOTE

TURN ON

REFERENCE 250

MONAURAL AMPLIFIER

VOLTS

SERIAL

0 4 8 16

INPUT

200K BAL

PLYMOUTH, MINNESOTA

MADE IN U.S.A.

900W MAX 50/60 HZ ~

RISK OF ELECTRIC SHOCK

DO NOT OPEN

CAUTION !

WARNING

RISK OF HAZARDOUS ENERGY!

MAKE PROPER SPEAKER CONNECTIONS

SEE OWNERS MANUAL

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.

CAUTION

FOR CONTINUED PROTECTION AGAINST

FIRE HAZARD REPLACE FUSE ONLY

WITH SAME TYPE AND RATING

XLR input

12V remote trigger

Speaker connections

Fuse holder

A.C. Mains connector

Back Panel Controls and Connections

Connections

Input Connectors

The Reference 250 SE uses a fully balanced

circuit topology and has a balanced XLR

input connector on the rear panel. It

therefore requires a balanced preamplier

output, as provided by most Audio

Research preampliers. Connect your

preamplier’s output to the Reference

250 SE before turning on the amplier.

Output Connectors

Heavy-duty output terminals are provided

on the rear panel for 4, 8, or 16-ohm

speaker impedance loads. Using high-

quality speaker cables, securely fasten the

(-) speaker lead to the appropriate (black)

terminal, then the (+) lead to the matching

(red) terminal. Follow your speaker

manufacturer’s impedance specication.

The Reference 250 SE puts out the

same amount of power whether the

4, 8, or 16-ohm terminals are used.

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.

Connect the Reference 250 SE input

to the preamplier or electronic

crossover, using only the highest

grade of audio interconnect cables.

To avoid sonic degradation use the

shortest practical length of cables.

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). Connect the black or ‘–‘ speaker

terminal to the wire that connects to

the 0 terminal on the Reference 250 SE.

Connect the red or ‘+’ speaker terminal

to the wire that connects to the 4, 8, or

16 ohm terminal on the Reference 250

SE and tighten the speaker terminals

securely to ensure best sonic results.

Connections

Remote Turn-on

The Reference 250 SE has a built-in 12V DC

remote turn-on/o circuit for operation

by a master control system in a home

theater or large audio system. Use a

3.5mm (.140”) diameter mono mini

plug to connect to the +12V IN jack on

the rear of the Reference 250 SE.

The +12V IN jack should be connected to

the +12V DC output of the master control

system, using a continuous +12V DC signal

at 12mA per Reference 250 SE for the

duration of amplier on-time. Do not use

a momentary or data pulse control signal.

The +12V DC remote jacks have polarity

protection, so they will not operate if a

-12V DC signal is accidentally connected,

or if the control wires are reversed.

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