Conrad-johnson design Evolution 20 Manual de usuario

Conrad-Johnson Owner’s Manual:

Evolution 20 Vacuum-Tube Preamplifier

conrad-johnson It just sounds right.

Congratulations on your purchase of the conrad-johnson Evolution 20

vacuum tube preamplifier. You have acquired one of the finest pieces of

music reproduction equipment available today. The result of more than

a decade of research by conrad-johnson design into the application of

vacuum tube devices to the reproduction of recorded music, the Evolu-

tion 20 was designed to establish the reference standard among pream-

plifiers for reproducing the dynamics, tonalities, textures and ambience

of a live musical performance. The design and materials have been

carefully selected to yield years of unvarying excellence.

Please take a few minutes to read this manual so that you will better

understand the features and capabilities of your Evolution 20. NOTE

THAT THE Evolution 20 LINE STAGE IS PHASE INVERTING.Seethe

section entitled "Getting the most from your Evolution 20" for details on

correct hookup in your system.

EVOLUTION 20 OWNER’S MANUAL 1

LIMITED WARRANTY FOR THE conrad-johnson

Evolution 20

1. conrad-johnson design, inc. warrants to the original purchaser that

the Evolution 20 will be free of defects in materials and workmanship

for a period of three years from the date of original purchase.

2. conrad-johnson will repair defective units without charge for labor or

parts (with the exception of the vacuum tubes) subject to the following

conditions:

a) The unit must not have been altered or damaged through

misuse, abuse, negligence, accident, or improper operation.

b) The purchaser must provide evidence of purchase at the time

service is requested.

c) All repairs must be undertaken at the factory or other service

center designated by conrad-johnson design, inc. Units submitted

for warranty repairs must be shipped in the factory packing carton

to conrad-johnson design or its designated service center, freight

and insurance prepaid by the owner, and will be returned to the

owner, freight and insurance prepaid by conrad-johnson design.

Replacement cartons are available from the factory for a nominal

charge.

d) Normal wear and maintenance are not covered by this warranty.

3. The above warranty may be transferred to subsequent owners pro-

vided that the warranty registration card has been returned to conrad-

johnson design, inc. within 30 days of the original purchase and that the

registered owner provides the factory with a signed notice giving the

newowner’snameandaddressandthemodelandserialnumberofthe

unit.

4. Where permitted by law, conrad-johnson design’s liability shall be

limited to that set forth in this warranty. No other warranty of any kind,

expressed or implied, is made by conrad- johnson design, inc., and all

implied warranties, including merchantability and fitness for a particular

"purpose", which exceed the obligations and time limits set forth herein

are hereby disclaimed. conrad-johnson design, inc. shall not be liable

for incidental or consequential damages. Some states do not allow the

exclusion or limitation of incidental or consequential damages, or limita-

tions on how long an implied warranty lasts, so the above limitations or

exclusions may not apply to you.

EVOLUTION 20 OWNER’S MANUAL 2

4. This warranty gives you specific legal rights, and you may also have

other rights which vary from state to state. Questions about warranty

service should be addressed to:

Service Department

conrad-johnson design, inc.

2733 Merrilee Drive

Fairfax, VA 22031

REGISTERING THE WARRANTY

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

chasetoregisterthewarranty.Thewarrantymaybetransferredtoanew

owner if it has been properly registered initially and if the registered

owner sends a signed notice providing the name and address of the

new owner and the model and serial number of the unit.

Proper registration of the warranty is important! Not only will it preserve

transferability of your warranty, it will also enable us to inform you of any

alterations in the design of a given model and of any new products we

offer which are likely to be of interest to you.

EVOLUTION 20 OWNER’S MANUAL 3

INSTALLATION

Because of the number and type of vacuum tubes used, the Evolution

20 dissipates a significant amount of heat (approximately 50 watts). It is

essential, therefore, that proper attention be paid to ventilation. The unit

should be mounted horizontally on a flat hard surface so that the

ventilation holes in the bottom are unobstructed. At least three inches of

clearance should be provided above the unit and the cabinet or shelf

should be open at the back. Vertical installation is not recommended.

To minimize hum pickup, keep the unit well away from the power

amplifier, and route power cords away from input cables.

The Evolution 20 requires an ac power line providing between 108 and

125 volts at 50 to 60 Hz. Alternatively, the Evolution 20 is optionally

available for operation on 100, 220, or 240 volt power lines.

CONNECTION

Phono input: This input provides the amplification and equalization

requiredby moving magnet and mostmoving coil cartridges. The phono

input impedance can be selected by a back panel switch. The options

are 70,100,150,250,470,1k,2k,5k,10k and 47k ohms. Most moving

magnet cartridges will sound best at the industry standard 47k setting,

thoughsomemaybenefitfromloadingat10k.Movingcoilcartridgesare

morevariable, and werecommendauditioningthe system tochoosethe

load most suitable for your cartridge.

Tuner, cd, tape 1, tape 2: These are high level inputs and are electri-

cally equivalent. They present approximately a 20k ohm load to the

source.Theoutputs of your tape recorders should be connected totape

1 and tape 2.

Record output: The record outputs connect the selected signal to your

recorders or external processing loop (eg. equalizer). The output signal

is not affected by the level control. Connect "record out" to the inputs of

your tape recorders or external processors.

Output 1, Output 2: Connect these outputs to the input of your ampli-

fier(or crossover in a bi-amped system). We recommend the use of an

EVOLUTION 20 OWNER’S MANUAL 4

amplifier with an input impedance of 10k ohms or higher. Since the line

stage of the Evolution 20 inverts phase, it may be necessary to invert

the speaker leads to maintain correct absolute phase. See the section

on "Getting the most out of your Evolution 20" for an explanation of this.

USE OF EXTERNAL TONE CONTROLS OR OTHER

EXTERNAL SIGNAL PROCESSING DEVICES:

Use Tape 1 and Record 1 for your tape recorder. Connect the output of

the tone controls to Tape 2 and the input of the tone controls to Record

2. To use the tone controls, select Tape 2 on the Source Selector and

use the Record Selector to select phono, tuner, cd or tape 1. By

selecting the input directly on the source selector, the tone control

processor will be bypassed.

EVOLUTION 20 OWNER’S MANUAL 5

CONTROLS

OFF, POWER: Because of the delayed warmup characteristics of vac-

uum tube equipment, a time delay muting circuit is incorporated in this

preamplifier. The main outputs are grounded via relays for approxi-

mately 90 seconds after the unit is turned on in order to suppress

warm-up transient noises. The relay grounds the outputs again immedi-

ately at turn off or in the event of any power line interruption.

SOURCE SELECTOR: PHONO, TUNER, CD, TAPE 1, TAPE 2: This

selector switch is used to choose an input for listening.

RECORD SELECTOR: PHONO, TUNER, CD, TAPE 1, TAPE 2.: This

control selects the signal to the record outputs, allowing the user to

record one source while listening to another.

BALANCE: The balance control is an eleven position stepped attenu-

ator that is out of the circuit at the center position. Each step away from

center attenuates the opposite channel by approximately .75 dB. At the

full extreme position positions, there is about 3.75 dB difference be-

tween the two channels.

LEVEL: The Evolution 20 volume control is a twenty-three position

stepped attenuator, selecting among twenty-three pairs of precision

resistors.

EVOLUTION 20 OWNER’S MANUAL 6

VACUUM TUBE REPLACEMENT

Each channel of the Evolution 20 uses five vacuum tubes: one 6CW4

and four 6GK5s. Each type has been carefully chosen for its particular

circuit application. It is well known that tubes of a given type vary

sonically depending on the manufacturer. We have chosen the brands

of tubes we supply based on extensive auditioning of available brands

with the choices being made solely on the basis of sonic performance

without regard for either cost or prestige. We know of no vacuum tubes

availablewhichwillimprovethesonicperformanceofyourEvolution20.

In addition, 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. We anticipate two to three

years of operation without degradation in normal use. The tubes have

also been hand selected to achieve the minimum residu al noise in your

preamplifier. Therefore, we highly recommend that when the time

comes to replace the vacuum tubes, you purchase replacement tube

sets from conrad-johnson design.

Refer to the diagram on the next page for tube locations.

EVOLUTION 20 OWNER’S MANUAL 7

EVOLUTION 20 TUBE COMPLEMENT

V1 and V2 type 6CW4

V3-V10 type 6GK5

V3 V1 V2 V4 V8 V7

V5 V6 V10 V9

EVOLUTION 20 OWNER’S MANUAL 8

GETTING THE MOST FROM YOUR EVOLUTION

The conrad-johnson Evolution 20 offers an unparalleled level of sophis-

tication and refinement in music reproduction, but it cannot transform an

inferior stereo system. Only high quality amplifiers and loudspeaker

systems will be capable of fully revealing the capabilities of this preci-

sion instrument.

Given a system of high quality components, there remain 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 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 loudspeak-

ers. 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 is either phase correct or phase inverting (including the source

and speakers-these are normally phase correct). It is of no conse-

quence if an individual component is phase inverting, as long as the

system as a whole is phase correct. This will be the case as long as the

number of phase inversions is even (or zero).

The line stage of the Evolution 20 is PHASE INVERTING. It inverts the

phase of all inputs, including phono. If your system has an odd number

of inversions, then you must add one phase inversion. This will be the

case if the Evolution 20 is the only unit in the chain that inverts phase.

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

EVOLUTION 20 OWNER’S MANUAL 9

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