Conrad-Johnson ET7 User manual

Conrad-Johnson Owner’s Manual:
ET7 Vacuum-Tube Line-Stage reamplifier
conrad-johnson It just sounds right.

Conrad-Johnson ET7 Owner’s Manual
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Thank you for selecting the conrad-johnson ET7 preamplifier as
the control center for your audio system. Embodying more than
four decades of research at conrad-johnson into the reproduction
of recorded music, the ET7 preamplifier excels at the recreation of
the dynamics, textures, tonalities, and ambience of live musical
performances. 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 the ET7 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
ET7. Note that this unit is phase inverting. See the section entitled
“Getting The Most From Your ET7" 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 ET7, 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 ET7 Owner’s Manual
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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.

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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.
2800K Dorr Avenue
Fairfax, VA 22031
The conrad-johnson service department can also be reached by e-
mail at [e-mail], 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 ET7 Owner’s Manual
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Installation
Set Up
To maintain proper ventilation, mount the ET7 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.
All ET7s 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 ET7 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 ET7 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
center conductors, and a separate external shield connected at
only one end).

Conrad-Johnson ET7 Owner’s Manual
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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.

Conrad-Johnson ET7 Owner’s Manual
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Connection
SOURCES (PH/AUX, TUNER, CD, VIDEO, AUX2): These high
level inputs are electronically equivalent. The load they present to
the source varies with the volume control setting, but in no case
will it drop below 12 kOhms. Connect the corresponding source
components to these inputs.
EPL1: A set of line-level inputs and outputs provided for
connection of external signal processors (e.g. parametric equalizer,
tone controls). These can also be used for the connection of a tape
recorder. In this case, connect the EPL OUT to the recording input
of your tape recorder, and the EPL IN to the output of your tape
recorder. The EPL IN connection can also be used as an additional
line level input.
THEATER: This is an external processor loop designed to
conveniently accommodate the addition of a surround-sound
processor (SSP) to a high-quality two-channel system without
compromising two-channel performance. Connect the front left and
front right channel outputs from your SSP to the EPL2 input. You
can also connect the THEATER OUT to an input on your SSP,
allowing you to do matrix processing on selected two channel
sources. When THEATER is selected, the level controls are set to
unity gain. Level and balance control is then accomplished via your
surround sound processor.
MAIN OUT: Two pairs of main outputs are provided. 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 the ET7 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 ET7" for
an explanation.

Conrad-Johnson ET7 Owner’s Manual
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Controls
<power>: Press the switch labeled power to switch the
preamplifier on. A time delay auto-muting circuit is incorporated
into the ET7 to eliminate transients generated by the warm-up, and
cool down cycles of the vacuum-tubes. All outputs are grounded
via relays for approximately 60 seconds after the unit is turned on
in order to suppress warm-up transient noises. During this auto-
muting period, the mute indicator led will flash. All control functions
are disabled during the auto-muting cycle. The muting relay also
grounds the outputs immediately at turn-off or in the event of any
power line interruption. When the ET7 is turned off (by pressing the
power switch again), the standby led will be illuminated.
When first connected to ac mains, or after an interruption of power,
the ET7 will turn on in a default mode (after auto-muting), with the
level set at 20, and the CD input selected. In subsequent sessions,
as long as the ac mains supply has not suffered a power outage,
the unit will turn on at the last used volume setting and input.
<mute>: Pressing the mute button will silence the preamplifier’s
main outputs, and set the level display to zero on both channels.
Pressing the mute button again will restore the previously selected
level setting.
<vol up>, <vol dn>: Level setting on the ET7 is achieved by using
a programmed microprocessor to select combinations from among
an array of high-quality precision resistors. This arrangement
allows 100 steps of approximately .7 dB per step. The steps are
numbered 0 through 99, with 0 being silence, and 99 being
maximum volume.
The level setting can be changed by pressing the vol up and vol dn
buttons on the front panel. Each time a button is pressed, the level
will move up or down one step. If a button is pressed and held, the
level control will cycle through the steps at an accelerating rate.
With each step, a slight “click” will be heard from the opening and
closing relays inside the ET7. Balance can only be set using the
remote control.
<source>: Pressing the button labeled source will cause the unit
to step through the five source inputs (ph/aux, tuner, cd, video,
aux2). The selected input will be indicated by an illuminated led.
<epl/thtr>: Pressing the epl/thtr button will cause the unit to step
from source through epl1 and theater. When source is selected,
the input selected by the source selector will be passed directly to

Conrad-Johnson ET7 Owner’s Manual
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the volume control. When the EPL1 or THEATER inputs are
selected, the selected source will first pass through the external
processor loop before being routed to the volume control. When
THEATER is selected, the level will be set and locked to unity gain.
Remote Control
All operations of the ET7 can be controlled by the wireless remote
unit.
MUTE: Pressing the mute button will cause the main outputs to
mute and the level display to be zero. Pressing it again will restore
the last level setting. Pressing and holding the mute button for
more than three seconds will switch the ET7 into standby mode (all
tube circuitry switched off). Pressing the mute button when the unit
is in standby mode will switch it back on.
SELECTORS (PH/AUX, TUNER, CD, VIDEO, AUX2): You can
directly access any of these inputs by pressing the associated
button on the remote.
EPLS (EPL1, EPL2): Pressing the EPL buttons inserts the
associated processor in the signal path. Pressing the button again
will re-establish a direct connection to the selected source.
Pressing the EPL2 button selects the THEATER input, setting the
level to unity gain.
LEVEL (+, -): Duplicates the function of the front panel <vol up>,
<vol dn> controls.
BALANCE: Allows attenuation of either channel independently of
the other. Pressing the right balance button will reduce the left
channel level setting by one step. Pressing and holding the right
balance button will cause the left channel to cycle down through its
level settings at an accelerating rate. Pressing the left balance
button will attenuate the right channel in the same manner.

Conrad-Johnson ET7 Owner’s Manual
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Vacuum Tube Replacement
The ET7 circuit employs one vacuum tube, a 6922. The 6922
offers low noise, low microphonics, and gain well suited to use in a
zero-feedback line-stage. The brands of tubes we supply have
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 ET7. The tubes that we
supply have been tempered by a controlled burn-in procedure that
permits them to perform for a greatly extended period without sonic
degradation, and 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 ET7 Owner’s Manual
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Getting the Most from Your ET7
In a system of commensurate high quality components, the
conrad-johnson ET7 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
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 ET7 is phase inverting. If your system has an odd number of
inversions, (for example, if the ET7 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 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 ET7 Owner’s Manual
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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 ET7 before listening: The sonic performance of the
ET7 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 ET7 do not hesitate to call Customer Service at (703) 698-
8581.

Conrad-Johnson ET7 Owner’s Manual
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Specifications
Gain: 25 dB
Maximum Output: 20V rms
Bandpass: 2Hz to more than 100kHz
Hum and Noise: 100 dB below 2.5V output
Distortion at 1.0 V output: less than .15% THD or IMD
Phase: inverts phase of all inputs at main out
Ouput Impedance: 100 ohms
Mechanical
Dimensions: 15.375"D x 19"W x 4.375"H
Net Weight: 19 lbs.
Fuses
The ET7 has two power transformers (one for the tube circuitry,
one for the control circuits), each of which is protected by a fuse. In
addition there is one fuse on the ac mains. A failure of any of these
fuses is a symptom of a more serious problem, and a competent
service technician should be consulted. In no event should these
fuses be replaced with a value or type different than that originally
supplied. Two of the fuses, F1 and F2 are located on the main pc
board near the power transformers. The third fuse, F3, is in a tray
that is part of the IEC power line connector. The correct fuse
values are:
If configured for 100 or 120V:
F1 5 x 20 mm 500 mAmp, fast blow
F2 5 x 20 mm T400 mAmp, slow blow
F3 5 x 20 mm T800 mAmp, slow blow
If configured for 220 or 240V:
F1 5 x 20 mm 200 mAmp, fast blow
F2 5 x 20 mm T200 mAmp, slow blow
F3 5 x 20 mm T400 mAmp, slow blow