Conrad-Johnson ART 108A Bedienungsanleitung

Conrad-Johnson Owner’s Manual:

ART 108A Amplifier

conrad-johnson It just sounds right.

Conrad-Johnson ART 108A Amplifier Owner’s Manual 1

Thank you for selecting the ART 108A Amplifier to power your

audio system. The ART 108AAmplifier draws on four 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 ART 108A Amplifier, 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 asource 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 aview to maintaining optimal

performance over the years. Our reputation for producing among

the industry's most reliable components is anatural consequence

of this engineering approach.

Although operation of the ART 108A Amplifier is quite

straightforward, please take afew 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. Wewant 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 ART 108A Amplifier, 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 ART 108A Amplifier Owner’s Manual 2

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

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, fuses, and 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 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 which vary from state to state.

Conrad-Johnson ART 108A Amplifier Owner’s Manual 3

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 service@conradjohnson.com or by phone at 703-698-8581.

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 ART 108A Amplifier Owner’s Manual 4

Installation

As is the case with any vacuum-tube power amplifier, the ART

108AAmplifier dissipates a significant amount of heat. Mount the

unit on an amp stand. The ART108A should be unobstructed on all

four sides and top to provide adequate ventilation.

All ART 108A 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 ART 108A Amplifier 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. The ART108A should be powered "OFF"

when not in use.

Electromagnetic Interference (EMI)

Considerable care has been taken in the design of the ART

108AAmplifier 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.

Conrad-Johnson ART 108A Amplifier Owner’s Manual 5

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.

Connection

INPUT: Connect the preamplifier to your ART 108A Amplifier at

the RCA type connector located on the back of the amplifier.

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

your loudspeakers, with correct spacing to accept astandard

"double banana" plug. They will also accept spade lugs, bare wire,

or pin connectors.

In astereo system, the two channels should be connected in

correct "relative phase". This means that when the samesignal 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 arecording of asolo vocalist (use amono 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.

Conrad-Johnson ART 108A Amplifier Owner’s Manual 6

Vacuum Tube Replacement

The ART 108A Amplifier uses eleven vacuum tubes of two

different types: three type 6922 (V1, V2, V3,) and eight type

KT88 (V4-V11).The ART 108A amplifier was designed

exclusively for the use of KT88’s. We know of no vacuum tubes

available which will improve the sonic performance of your ART

108A Amplifier.

Note: To maintain performance and reliability, KT88

output tubes for the ART 108A must be replaced with

matched quads selected for use with this amplifier.We

highly recommend that you purchase replacement tubes from

conrad-johnson design.

Weanticipate tube life to accommodate two to three years

of operation without degradation in normal use - the amplifier

should be switched off when not in use.

The ART 108A Amplifier has been designed to make

tube replacement as simple as possible. No a-c balance

adjustment is necessary. It is necessary to re-bias the amplifier

when the output tubes are replaced. The ART 108A Amplifier

has built in bias indicators so that no instruments are

required to make this adjustment.

Conrad-Johnson ART 108A Amplifier Owner’s Manual 7

Adjusting Output Tube Bias

Biasing the amplifier is a simple procedure that can easily be done

by the owner. Only aplastic bias tool is required (one has been

included with your amplifier for this purpose). After installing the

tubes, the amplifier should be connected to aload (your

loudspeakers will work fine) and there should be no signal applied

to the amp. It should be connected to your preamplifier with the

volume control turned fully down. Turn the amplifier on. After three

minutes, turn each of the eight bias adjustment controls

(located near the output tube socket) clockwise until the

associated indicator LED turns on “AMBER.” Do not turn the bias

adjustment control any further in the clockwise direction once the

LED turns on “AMBER.” If the LED turns on “RED”, turn the

bias adjustment control counterclockwise until the LED turns on

“AMBER”.

After the amplifier has warmed up thirty minutes, the procedure just

described should be repeated. NOTE: It is normal for these

LEDs to flash or flicker “RED” when the amplifier is in use. This

biasing procedure should be performed whenever the

amplifier's output tubes are replaced and after each six months of

average use.

PLATE FUSE: Your ART 108A Amplifier has been fitted with a

plate supply fuse that is installed to protect the amplifier

circuitry in the event of output tube failure. The fuse holder is

physically located on the back panel, near the speaker binding

post. The cap unscrews counter-clockwise to remove the fuse

(KTK 2).

What happens when the fuse blows? A blown plate fuse

usually indicates a marginal output tube and an attempt should be

made to identify and replace it, by replacing the fuse and

turning on the amp while watching the output tubes carefully;

look for a bright white or blue flash inside the tube. If the tubes

have more than 1,500 hours on them, a complete replacement

tube set is probably in order.

The sonic effects of a blown fuse are very low, very distorted

sounds from the speaker being driven by that channel.

TO AVOID SHOCK, ALWAYS TURN OFF THE AMPLIFIER

BEFORE REMOVING THE FUSE HOLDER CAP

Replacement fuses are available from conrad-johnson dealers

and directly from conrad-johnson design.

Conrad-Johnson ART 108A Amplifier Owner’s Manual 8

Getting The Most From Your ART 108A Amplifier

In a system of commensurate high quality components,

the Conrad-Johnson ART 108A 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 arise in

pressure. The ear is capable of distinguishing these positive

transients from the musically unnatural alternative of anegative

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 afall 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 awhole is phase correct. This will be the case if the

number of phase inversions is even (or zero).

The ART 108A Amplifier 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.

Conrad-Johnson ART 108A Amplifier Owner’s Manual 9

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 ART 108A Amplifier before listening: The

sonic performance of the ART 108A Amplifier 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 ART 108A Amplifier, do not hesitate to call

Customer Service at (703) 698-8581.

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