Conrad-Johnson Classic 2 Manual de usuario

Conrad-Johnson Owner’s Manual:

Classic 2 Preamplifier

conrad-johnson It just sounds right.

Conrad-Johnson Classic 2 Preamplifier Owner’s Manual

Thank you for selecting the Conrad-Johnson Classic Preamplifier

as the control center for your audio system. Using it, we believe

that you will hear more from your favorite recordings than ever

before. Drawing on nearly three decades of research at conrad-

johnson into the reproduction of recorded music, the Classic

Preamplifier excels at the recreation of the dynamics, textures,

tonalities, and ambience of live musical performances.

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 have been

selected with a view to maintaining optimal performance over the

years. Our reputation for producing among the industry's most reli-

able components is a natural consequence of this engineering

approach.

Although the Classic has been designed to operate in an intuitively

apparent way, you will find useful information on its installation and

operation in this manual. Please take a few minutes to read the

manual to better understand the features and capabilities of your

Conrad-Johnson preamplifier. Note that this unit is phase inverting.

See the section entitled "Getting the Most from Your Classic

Preamplifier" for details on correct hookup in your system.

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 Classic

Preamplifier, and to provide any needed service both during, and

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

recorded music.

Conrad-Johnson Classic 2 Preamplifier Owner’s Manual

Limited 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 origi-

nal 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 which have been damaged by misuse, abuse, or acci-

dent.

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 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 inci-

dental 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 which vary from state to state.

Conrad-Johnson Classic 2 Preamplifier Owner’s Manual

Conrad-Johnson products purchased outside the United States are

covered by warranty terms of the importing distributor in the coun-

try in which the product was originally purchased, which may differ

from the terms set out herein. Importing distributors are not obli-

gated 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.

2733 Merrilee Drive

Fairfax, VA 22031

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

mail at service@conradjohnson.com, 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

Conrad-Johnson Classic 2 Preamplifier Owner’s Manual

Installation

The Classic Preamplifier dissipates up to nearly 30 watts of heat,

and must be adequately ventilated. Mount the unit horizontally on a

flat, hard surface, and take care that the ventilation holes in the

bottom are unobstructed. Allow at least two inches of clearance

above the unit and keep the cabinet or shelf open at the back.

Vertical installation is not recommended.

All Classics 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 Classic Preamplifier 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 Classic

Preamplifier to minimize its susceptibility to radio frequency inter-

ference and other forms of EMI. Choice of materials, physical lay-

out, 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 applica-

tion, 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).

Conrad-Johnson Classic 2 Preamplifier Owner’s Manual

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

minimizing hum pickup. The installation should situate the pream-

plifier 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

SOURCES (TUNER, CD, VIDEO, TAPE): These high level inputs

are electrically equivalent. These inputs present a 20 kOhm load to

the source. Connect the corresponding source components to

these inputs.

AUX1/PH: If the optional phono stage is installed, this input

provides the extra gain and RIAA equalization required for play-

back of LPs. Otherwise, this serves as an additional line-level

input.

MAIN OUT: Connect to the input of your amplifier (or crossover in

a bi-amplified system). We recommend the use of an amplifier with

an input impedance of 20k ohms or higher. Since this preamplifier

inverts phase, it may be necessary to invert the speaker leads to

maintain correct absolute phase. See the section on “Getting the

Most From Your Classic Preamplifier" for an explanation.

Conrad-Johnson Classic 2 Preamplifier Owner’s Manual

Controls

<power>: Press the switch labeled power to switch the

preamplifier on. A time delay auto-muting circuit is incorporated

into the Classic Preamplifier to suppress turn-on/turn-off transients.

All outputs are grounded via relays for approximately 45 seconds

after the unit is turned on in order to suppress warm-up transient

noises.

volume: The Classic Preamplifier features a high-quality, precision

tracking volume control.

source selector (aux1/phono, tuner, cd, video, tape): Rotate the

knob to select the desired input.

load impedance switch (inside chassis, units with installed

phono board only): To select a phono input impedance of less

than the factory preset 47 kOhms on units with installed optional

phono stage, unplug the Classic Preamplifier from the ac mains

and remove the cover. The input impedance is set by the load

selector switches – the two dual inline pin (dip) switch arrays

located near the input connectors at the back of the preamp. Each

dip array includes four switches labeled 1 through 4. Load

impedances are selected by setting switches as follows:

Impedance switch #

1 2 3 4

47 kOhms o o o o

9.6 kOhms x o o o

1.9 kOhms o x o o

500 Ohms o o x o

200 Ohms o o o x

x indicates switch in “on” position

o indicates switch in “off” position

note: off position is indicated by arrow on the body of the switch

array.

Be sure to set both switches the same. When done, replace cover.

Do not operate unit with cover off.

Conrad-Johnson Classic 2 Preamplifier Owner’s Manual

Vacuum Tube Replacement

The line stage audio circuit of the Classic Preamplifier uses a

single type 6922 miniature twin-triode vacuum tube (V1). Units with

the optional high-gain phono stage have three additional tubes – all

type 12AX7 (V3, V4 and V5). Units with the optional low-gain

phono stage have two type 12AX7 (V3 and V4) and one type

12AU7 (V5). The brand of tubes we supply has been chosen by

first selecting those brands which are known to be most reliable,

then by extensive auditioning of these acceptable brands with the

final choices being made solely on the basis of sonic performance.

We know of no vacuum tubes available which will improve the

sonic performance of your Classic Preamplifier. The tubes in your

preamplifier have been tempered by a controlled burn-in procedure

that permits them to perform for a greatly extended period without

sonic degradation, then selected for minimum residual noise.

Replacement tubes are prepared and selected in the same way.

Therefore, we highly recommend that you purchase replacement

tube sets from conrad-johnson design. We anticipate tube life to

accommodate two to three years of operation without degradation

in normal use - if the preamplifier is switched off when not in use. If

the preamplifier is left on at all times, tube life can be exhausted in

a matter of a few months.

Conrad-Johnson Classic 2 Preamplifier Owner’s Manual

Getting the Most from Your Conrad-Johnson Classic

In a system of commensurate high quality components, the

conrad-johnson Classic Preamplifier offers 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 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 pres-

sure. 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 Classic Preamplifier is phase inverting. If your system has an

odd number of inversions, (for example, if the Classic is the only

phase inverting unit in the chain) 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 espe-

cially 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 investiga-

tion of absolute phase.

Conrad-Johnson Classic 2 Preamplifier 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 ref-

erence 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 sys-

tem 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 Classic before listening: sonic performance will

improve 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 Classic Preamplifier do not hesitate to call Customer

Service at (703) 698-8581.

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