Conrad-Johnson MF2275 Manuel utilisateur

Conrad-Johnson Owner’s Manual:

MF2275 Power Amplifier

conrad-johnson It just sounds right.

MF2275 Owner’s Manual

Thank you for selecting the MF2275 amplifier to power your audio

system. The MF2275 draws on three decades of research at

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

is a power amplifier with a remarkable ability to recreate the

dynamics, textures, tonalities, and ambience of live musical

performances. With the MF2275, we believe that you will

experience the excitement 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 conrad-

johnson 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 MF2275 amplifier is quite

straightforward, please take a few minutes to read this manual for

useful information on its installation and operation.

In closing, we’d like to welcome you to the family of conrad-

johnson owners. We want you to enjoy your conrad-johnson

product to the fullest. To this end, our staff stands ready to answer

any questions you may have about the function and application of

your MF2275, and to provide any needed service both during, and

after the warranty period. Our goal is to heighten your enjoyment of

recorded music.

MF2275 Owner’s Manual

imited Warranty For Conrad-Johnson Components

Conrad-Johnson Design, Inc. will provide service under warranty to

the original owner on 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 conrad-johnson dealer. During the warranty period,

conrad-johnson will repair defective units without charge for labor

or parts (with the exception of vacuum tubes and batteries).

Exclusions. The following are not covered under this warranty:

a) Units that have been damaged by misuse, abuse, or

accident.

b) Units that have been modified, altered, or improperly

repaired by anyone not specifically authorized by conrad-

johnson design, inc.

c) Units not purchased from an authorized conrad-johnson

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 insurance prepaid by the owner. After repair, the

unit will be returned with freight and insurance prepaid by conrad-

johnson design to any destination in the United States.

All implied warranties, including merchantability and fitness for a

particular 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 that vary from state to state.

MF2275 Owner’s Manual

Conrad-Johnson 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 States, but in

these cases, 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.

2800K Dorr Avenue

Fairfax, VA 22031

The conrad-johnson service department can also be reached by e-

mail at [email protected], by phone at 703-698-8581,

or by fax at 703-560-5360.

Service

If your conrad-johnson audio component requires service, repack it

using the original box and packing material and ship to the Service

Department address above. Boxes and packing materials can be

purchased through our service department if you no longer have

yours. Include with the unit a note describing the problem you are

having 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 approval before

commencing service.

Registering The Warranty

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

purchase to register the warranty

MF2275 Owner’s Manual

nstallation

As is the case with most power amplifiers, the MF2275 amplifier

dissipates a significant amount of heat. Provision must be made for

adequate ventilation. 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 MF2275 amplifiers sold in the United States are configured for

operation on a 60Hz ac power line producing between 108 and 126

volts. Export versions of the MF2275 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 MF2275 to

minimize its 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

compromising the performance of our product in the 99.9% of

installations where EMI is not a problem.

Care in installation can often avoid EMI induced problems. The

following 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

MF2275 Owner’s Manual

center conductors, and a separate external shield connected at

only one end).

Physical location and cable “dress” can be an important factor in

minimizing 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.

MF2275 Owner’s Manual

onnection

INPUT: Connect the preamplifier to your MF2275 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 banana" plug. They will also accept spade lugs, bare wire,

or pin connectors.

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 available). With the speakers in

phase the voice should be clearly focused between the two

speakers. With the speakers connected out of phase, the voice will

be diffused, with no identifiable source. Relative phase may be

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

MF2275 Owner’s Manual

etting The Most From Your MF2275 Amplifier

In a system of commensurate high quality components, the

conrad-johnson MF2275 amplifier offers an unparalleled 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 that must be attended to.

Absolute Phase

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

alternating rise and fall of air pressure. Musical transients are

almost exclusively positive: that is, the initial effect is a rise in

pressure. The ear is capable of distinguishing these positive

transients from the musically unnatural alternative of a negative

transient (an initial fall in air pressure). 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 MF2275 is phase correct (non-inverting). If your system has

an odd number of inversions, (for example, if you have a phase

inverting preamplifier) then you must add one phase inversion.

This is conveniently done by reversing the positive and negative

connections to your speakers (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 more sharply defined. The effect is especially apparent

on plucked string 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.

MF2275 Owner’s Manual

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 specific system.

Performance Tip

Warm up the MF2275 before listening: The sonic performance of

the MF2275 improves noticeably as the unit warms up. The

midrange becomes more lucid, the highs smoother, and the

soundstage expands. The warm up period can be expected to last

about fifteen minutes.

Questions: If you have questions about the installation or function

of your MF2275 do not hesitate to call Customer Service at (703)

698-8581.

MF2275 Owner’s Manual

pecifications

Power: 135 watts per channel RMS both channels driven into 8

ohms from 20Hz to 20KHz at no more than 1.0% total harmonic

distortion or intermodulation distortion.

Sensitivity: 1.35 V rms to rated power

Frequency Response: 20Hz to 20 kHz +0/-.3 dB

Hum and Noise: 100 dB below rated power output

Phase: phase correct

Input Impedance: 100 kOhms

Mechanical

Dimensions: 14.625"D x 19”W x 4.875”H

Net Weight: 33 lb. net

Fuses

There are 5 fuses in the MF2275. One is the ac power line (mains)

fuse. It is located in the IEC power cord receptacle. The other four

fuses are in the DC power supplies for the output stages one for

the positive (B+) and one for the negative (B-) supply to each

channel. These B+/B- fuses are located on the top of the main

printed circuit board. Be sure to disconnect the amplifier from the

ac mains power (wall outlet) before removing the top cover.

Never replace a fuse with a value or type different from that

originally supplied by the factory. Correct values and types are

listed below. In the event of a fuse blowing repeatedly, contact your

dealer or the conrad-johnson service department.

AC Mains Fuse: 5x20mm T-Type:

6.3 amp if configured for 100 or 120V

3.15 amp if configured for 220 or 240V

B+/B- Fuses: 3AG 4 Amp, fast blow

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