Conrad-Johnson Sonographe SA250 Manuel utilisateur

Thank you for selecting the Sonographe SA250 as the power amplifier

for your audio system. The SA250 draws on two decades of research at

conrad-johnson design into the reproduction of recorded music. The

result is an amplifier with a remarkable ability to recreate the dynamics,

textures, tonalities, and ambience of live musical performances. With

the Sonographe SA250, we believe that you will experience the excite-

ment of discovery in hearing more from your favorite recordings than

ever before.

At conrad-johnson, we expect our products to be a source of satisfaction

and of pride to their owners for many years to come. Accordingly, circuit

designs, parts and materials for all our products are selected with a view

to maintaining optimal performance over the years. Our reputation for

producing among the industry’s most reliable components is a natural

consequence of this engineering approach.

Although operation of the SA250 is quite straightforward, please take a

few minutes to read this manual for useful information on it’s installation

and operation.

We want you to enjoy your Sonographe product to the fullest. To this

end,ourstaffstandsreadytoansweranyquestionsyoumayhaveabout

the function and application of your SA250, and to provide any needed

service both during, and after the warranty period. Our goal is to

heighten your enjoyment of recorded music.

Sonographe SA250 Owner’s Manual 1

Limited Warranty For Sonographe Components

conrad-johnson design, inc. will provide service under warranty to the

original owner on Sonographe products sold new in the United States

for the lesser period of three years from the date of purchase by the

original purchaser, or five years from the date of shipment to the

authorized Sonographe dealer. During the warranty period, conrad-

johnson will repair defective units without charge for labor or parts (with

the exception of batteries).

Exclusions. The following are not covered under this warranty:

a) Units which have been damaged by misuse, abuse, or accident.

b) Units which have been modified, altered, or improperly repaired by

anyone not specifically authorized by conrad-johnson design, inc.

c) Units not purchased from an authorized Sonographe dealer in the

United States for use in the United States.

d) Normal wear.

e) Incidental or consequential damages are not covered under this

warranty. Some states do not allow the exclusion of incidental or

consequential damages, so this exclusion may not apply to you.

Obtaining Warranty Service:To obtain warranty service, the unit must

be shipped, along with evidence of purchase, in factory packing to

conrad-johnson design (or designated service center) with freight and

insuranceprepaidbytheowner.Afterrepair,theunitwillbereturnedwith

freight and insurance prepaid by conrad-johnson design to any destina-

tion in the United States.

Allimplied warranties,includingmerchantability andfitnessfor aparticu-

lar purpose are limited in duration to the duration of this express

warranty. Some states do not allow limitations on the duration of implied

warranties so the above limitations may not apply to you.

This warranty gives you specific legal rights and you may also have

other rights which vary from state to state.

Sonographe products purchased outside the United States are covered

by warranty terms of the importing distributor in the country in which the

product was originally purchased, which may differ from the terms set

out herein. Importing distributors are not obligated to provide warranty

service for products originally purchased outside their country. Conrad-

Johnson will provide warranty service for products outside the United

Sonographe SA250 Owner’s Manual 2

States, but the customer must pay all shipping, handling and customs

costs both to and from our Service Department.

Questions about this warranty should be addressed to:

Service Department

conrad-johnson design, inc.

2733 Merrilee Drive

Fairfax, VA 22031

The Service Department can also be reached by phone at 703-698-

8581, or by fax at 703-560-5360

Service

If your Sonographe audio component requires service, repack it using

the original box and packing material and ship to the Service Depart-

mentaddressabove.Boxes andpackingmaterialscanbe obtainedfrom

our service department for a nominal charge, if you no longer have

yours.Includewiththeunitanotedescribingtheproblemyouarehaving

in as much detail as possible. It is especially important for our technician

to know if the problem is intermittent. If you want an estimate of cost for

out of warranty service, be sure to request it in this note. Be aware that

requesting an estimate will delay service to your unit as we will have to

contact you for your approval before commencing service.

Registering The Warranty

Please return the enclosed card to the factory within 30 days of pur-

chase to register the warranty.

Sonographe SA250 Owner’s Manual 3

Installation

As is the case with any high-power amplifier, the SA250 dissipates a

significant amount of heat. Provision must be made for adequate venti-

lation. Mount the unit on a flat, hard surface, taking care that the

ventilation holes in the bottom are unobstructed. Maintain at least four

inches of clearance above the unit, and at least three inches on the

sides. The cabinet or shelf should be open at both front and back. For

more restricted installations, cooling fans are essential.

All SA250 amplifiers sold in the United States are configured for opera-

tion on a 60Hz ac power line producing between 108 and 126 volts.

Export versions of these amplifiers will have the correct operating

voltage and frequency clearly marked on the back panel of the unit, near

the ac power cord. In all cases, the actual line voltage should be within

+ 5/- 10% of the nominal rated voltage.

Electromagnetic Interference (EMI)

Considerable care has been taken in the design of the SA250 to

minimize susceptibility to radio frequency interference and other forms

of EMI. Choice of materials, physical layout, grounding practice, and

power supply design have all been specified with a view to reducing the

impact of electromagnetic fields on the performance of this unit. At the

same time, however, our primary goal is the accurate reproduction of

recorded music in the normal home environment, and we have elected

not to compromise this objective by the application of heavy-handed RFI

filters, or by using grounding practices that reduce RFI at the expense

of degraded audio performance. We find that the approach we have

taken has worked extremely well, resulting in only rare instances of EMI

problems which could be treated locally as needed, rather than compro-

mising the performance of our product in the 99.9% of installations

where EMI is not a problem.

Careininstallationcan oftenavoidEMIinducedproblems. Thefollowing

practices should generally be observed in any application, and will be

especially important where EMI may be a problem.

Interconnect cables should be kept as short as possible (3 meters or

less), and shielded cable should be used (cable which has two center

conductors, and a separate external shield connected at only one end).

Sonographe SA250 Owner’s Manual 4

Physical location and cable "dress" can be an important factor in mini-

mizing hum pickup. The installation should situate the preamplifier well

away from the power amplifier, and power (ac mains) cords should be

dressed to remain at least 4" (100mm) away from input/output cables.

Connection

INPUT: Connect the preamplifier to your amplifier at the RCA type

connectors located on the back of the amplifier.

OUTPUT: Five way binding posts are provided for connection of your

loudspeakers, with correct spacing to accept a standard "double ba-

nana" plug. They will also accept spade lugs, bare wire, or pin connec-

tors. The two channels should be connected in correct "relative phase".

This means that when the same signal is applied to both channels, the

right and left channels speaker diaphragms will move synchronously -

in and out together.

Terminals on speakers are usually coded - one designated "C",

"ground", "-" or black, the other designated "+" or red. "In phase"

connection of the speakers can normally be achieved by taking care to

connect the wire from the "+" amplifier terminal to the red or "+" coded

terminal on each speaker, and connecting the "-" terminal to the black

or "-" coded terminal on each speaker.

In phase connection of the speakers can be readily ascertained by ear.

Listen to a recording of a solo vocalist (use a mono recording if avail-

able). With the speakers in phase the voice should be clearly focused

between the two speakers. With the speakers connected out of phase,

thevoicewillbediffused,withnoidentifiablesource.Relativephasemay

be reversed by switching the "+" and "-" leads at one speaker only.

Sonographe SA250 Owner’s Manual 5

Getting The Most From Your Amplifier

In a system of commensurate high quality components, Sonograhpe

amplifiers offer a high level of sophistication and refinement in music

reproduction. To get the best performance out of any audio system,

there are a number of important details which must be attended to.

Absolute Phase

Musical notes are heard through the ear’s response to waves of alter-

nating rise and fall of air pressure. Musical transients are almost exclu-

sively positive: that is, the initial effect is a rise in pressure. The ear is

capable of distinguishing these positive transients from the musically

unnaturalalternativeof a negative transient (an initial fallinairpressure).

In terms of your stereo system, these transients are created by your

loudspeakers. If the speakers respond to musical transients by first

moving out, they are creating a rise in pressure, and the system is said

to be phase correct. If they respond by moving in, they create a fall in

pressure and the system is said to be phase inverting. Each component

in the stereo system either preserves the phase of the incoming signal,

and is said to be phase correct, or inverts the phase and is said to be

phase inverting. It is unimportant whether an individual component is

phase correct or phase inverting, as long as the system as a whole is

phase correct. This will be the case if the number of phase inversions is

even (or zero).

The SA250 is phase correct. If your system has an odd number of

inversions, then you must add one phase inversion. This is conveniently

done by reversing the positive and negative connections to your speak-

ers (be sure to reverse both channels).

If you are not sure about the phase of every piece in your system, you

can establish correct absolute phase by careful listening. When the

system is in correct phase, transients will be noticeably cleaner and

moresharplydefined.The effectisespeciallyapparenton pluckedstring

sounds. A final warning - not all recordings are phase correct (including

some "audiophile" recordings), so listen to several before concluding

your investigation of absolute phase.

Sonographe SA250 Owner’s Manual 6

The Importance Of Wires

Interconnect and speaker wires are an important element in your stereo

system. Interconnects are available which will permit a reference quality

system to blossom and fulfill its promise of musical reality. Others will

strangle the system to the point where it becomes little better than

average. To complicate matters, our experience suggests that the

choice of interconnects will be system dependent - those that are top

ranked on one system may be a poor choice for a different system.

Consult your conrad-johnson dealer for recommendations for your spe-

cific system.

Questions: If you have questions about the installation or function of

your amplifier do not hesitate to call Customer Service at (703) 698-

8581.

Sonographe SA250 Owner’s Manual 7

Specifications:

Power: 125 watts per channel RMS both channels driven into 8 ohms

from 20Hzto 20KHz with no more than 1% total harmonic distortion or

intermodulation distortion.

Gain: 25.5 dB

Phase: Phase Correct (non-inverting)

Frequency response: 20 Hz to 20 KHz +0, -.25 dB

Hum and noise: 96 dB below full power output.

Input impedance: 100K ohms.

Dimensions: 13.25"D x 17.125"W x 4.875"H

Weight: 30 lbs.

Fuses: The AC line fuse is user replaceable on the SA250. It is a type

3AG 7 amp slow-blow (5 amp slow-blow for 220 or 240V operation).

NEVER REPLACE THE FUSE WITH A TYPE OR VALUE DIFFERENT

FROM THAT ORIGINALLY SUPPLIED BY THE FACTORY. If the fuse

blows repeatedly, contact your dealer, or Conrad-Johnson’s service

department.

Sonographe SA250 Owner’s Manual 8

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