Conrad-Johnson MV100 User manual

OWNER’S MANUAL
MV100
VACUUM TUBE AMPLIFIER
conrad-johnson design
703-698-8581

Congratulations on your purchase of the conrad-johnson MV100 amplifier. You have acquired one of the
finer pieces of musical reproduction equipment available today. The MV100 is the result of conrad-
johnson design’s research into the application of vacuum-tube devices to the reproduction of recorded
music. 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 featues and
capabilities of your MV100.
MV100 Owner’s Manual 1

LIMITED WARRANTY FOR THE CONRAD-JOHNSON MV100
1.conrad-johnsondesign,inc.warrantstotheoriginalownerthattheconrad-johnsonMV100will perform
to specifications as published in the owner’s manual and that it will be free from defects in material 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 provided 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 new owner’s name and address
and the model and serial number of the 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
limitations on how long an implied warranty lasts, so the above limitation or exclusion may not apply to
you.
5. 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
MV100 Owner’s Manual 2

REGISTERING THE WARRANTY
Please return the enclosed card to the factory within 30 days of purchase to register the warranty.Proper
registration of the warranty is important! It will 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.
MV100 Owner’s Manual 3

CIRCUIT DESIGN
Ithas beenourexperiencethat simpledesignswithfew activestageswhenexecuted withcare andgreat
attention to detail will be both more musical and more reliable than overcomplicated alternatives.
Accordingly, the audio circuit of the MV100 is remarkably straightforward. A single triode input amplifier
is direct coupled to a cathode follower. This arrangement offers exceptional phase linearity. This stage
is direct coupled to a cathode coupled differential phase inverter using high current triodes to provide
balanced, low impedance drive to the push-pull output stage. The output stage utilizes paralleledEL34s-
atotaloffourperchannel. Thisstagefeaturesultralinearoperationwhichpermitshighpower levels while
greatly reducing the source impedance of the stage. As a result, the amplifier is capable of supplying the
large current demands of high amplitude musical transients driven into reactive speaker loads. A
substantial main power supply enables the MV100 to easily meet these extraordinary currentdemands.
Voltage regulators for the voltage amplifiers and phase inverters provide nearly absolute isolation of
these sensitive stages from the output stages.
MV100 Owner’s Manual 4

INSTALLATION
Because of the number and type of vacuum tubes, the MV100 dissipates considerable heat (approxi-
mately 250 watts at idle). 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 eight inches of clearance should be provided above the unit, and at least four
inches on the sides. The cabinet or shelf should be open at both front and back. For more restricted
installations, cooling fans are essential.
Thefront panel ofthe MV100 willfit in astandard 19" equipmentrack and isdesigned to carrythe weight
of the unit so that it may be rack mounted. Again, it is important that adequate clearance be provided
above so that ventilation is not impeded. About eight inches of the front of the rack should be left open
above the unit.
To minimize hum pickup, keep the unit well away from the preamplifier and turntable and route power
cords away from input cables.
THE MV100 IS TO BE OPERATED ONLY ON AC LINE VOLTAGE OF 108 TO 125 VOLTS.
The MV100 is available wired for 100 volt, 120V, 220V or 240 volt, 50/60 Hz current.
MV100 Owner’s Manual 5

CONNECTION
INPUT: Connect the preamplifier to your MV100 amplifier at the RCA type connections located on the
back of the amplifier.
OUTPUT: Terminal strips are provided for connection of your loudspeakers. They will accept bare wire
or spade lug connectors.
Three different taps- 4 ohm, 8 ohm, and 16 ohm are provided in addition to the "C" or ground tap.
Matching the rated nominal output impedance of your speakers with the amplifier output taps will not
necessarily guarantee optimum performance. The sound with a given set of speakers will vary with the
diffrent impedance taps. We suggest listening to each of the three taps to select the best match for your
speakers.
Thetwo channels should beconnectedin correct "relative phase".Thismeans that when thesamesignal
is applied to both channels, the right and left channels speaker diaphragms should move synchronously-
in and out together. Terminals on the speakers are usually coded-one designated "C", "earth", "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 4,8, or 16 ohm amplifier terminal marked on each channel to the red or "+" coded terminal on each
speaker, and connecting the "C" tap to the black or "-" coded terminal on each speaker.
In phase connection of the speakers can be readily ascertained by ear. With the preamplifier mode
switched into the MONO position, play a record of a solo vocalist. 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.
MV100 Owner’s Manual 6

GETTING THE MOST FROM YOUR CONRAD-JOHNSON MV100
The conrad-johnson MV100 offers an unparalleled level of sophistication and refinement in music
reproduction, but it cannot transform an inferior stereo system. Only the very best loudspeaker systems
will be capable of fully revealing the capabilities of this precision instrument. On the other hand, the
MV100 is ruthlessly revealing. For example, it can render unacceptable faults in the phonosystem which
may be just discernable with an amplifier of lower resolution.
Proper set-up is important in any high-fidelity system, but with state-of-the-art componentsitis essential.
Before attempting to evaluate the MV100, be sure that your phono system has been set up carefully
according to manufacturer recommendations. Adjustment of the cartridge vertical tracking angle can be
especially critical with modern stylus configurations.
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 alternating rise and fall of air pressure.
Musicaltransientsareexclusivelypositive:that is ,theinitialeffectisariseinpressure.Theeariscapable
of distinguishing these positive transients from the musically unnatural alternative of a negative transient
(an initial fall in air pressure). In 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 fallin 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 cartridge and speakers-these are normally phase correct). It is
of no consequence 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). If your
system has an odd number of inversions, then you must add one phase inversion. This is conveniently
done by reversing the positive and negative connections on either your cartridge or your speakers (be
sure to reverse both channels).
If you are not sure about the phase of every component 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 records are phase correct (including some "audiophile" recordings), so listen to several
before concluding your investigation of absolute phase.
MV100 Owner’s Manual 7

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 sytem to the point where it becomes no better than average. To complicate
matters, our experience suggests that the choice of interconnects will be system dependent-those that
are ranked first on a given system may be a poor choice for a different system. Consult your conrad-
johnson dealer for recommendations for your specific system.
QUESTIONS?
IfyouhaveanyquestionsabouttheinstallationorfunctionofyourMV100donothesitatetocallCustomer
Service at (703) 698- 8581.
MV100 Owner’s Manual 8

TUBE REPLACEMENTS
The MV100 uses twelve vacuum tubes of three different types: two 5751 (V1 and V2), two 6FQ7 (V3
andV4)andeightEL34s(V5throughV12). Each type has been carefully chosen for its circuitapplication.
Itiswellknownthattubesofagiven type vary sonically depending on the manufacturer. Wehave chosen
the brands of tubes that we supply based on extensive auditioning of available brands. The choice of
brand has been made solely on the basis of sonic performance and reliability without regard to either
cost or prestige. We know of no vacuum tubes available which will improve the sonic performance of
your MV100. Also, the tubes in your amplifier have been tempered by a controlled burn in procedurethat
permits them to perform for a greatly extended period without degradation in normal use. We highly
recommend that, when the time comes to replace the vacuum tubes, you purchase replacement tube
sets from conrad-johnson design.
The MV100 has been designed to make tube replacement as simple as posssible. Beacuase the output
tubes are individually biased, replacement tubes need not be matched pairs. NO a-c balance adjustment
is necessary. It is necessary to re-bias the amplifier when the output tubes are replaced. The MV100 has
built in bias indicators so that no instruments are required to make this adjustment.
ADJUSTING OUTPUT TUBE BIAS
Biasing the amplifier is a simple procedure that can easily be done by the owner. Only a plastic
screwdriver is required. A red plastic screwdriver has been included with your amplifier for this purpose.
After replacing the tubes, the amplifier should be connected to a load (your loudspeakers will work fine)
and there should be no signal applied to the amp. It should be connected to you preamplifier with the
volume control turned fully down. Turn the amplifier on. After about one minute, turn each of the eight
screwdriver adjustable controls (marked in the diagram) counterclockwise until the associated indicator
LED just goes off. Clockwise rotation may be necessary first to turn the LED on; do not turn the adjusting
screw any farther in the clockwise direction once the LED has come on.
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 when the amplifier is in use. This is normal and no
cause for alarm.
Thisbiasingprocedure shouldbeperformedwhenevertheamplifier’soutputtubesare replaced and also
after each six months of average use.
MV100 Owner’s Manual 9

Tube Locations:
TUBE COMPLEMENT: FUSE COMPLEMENT:
V1, V2 5751 Line Fuse: 3AG 10amp slo-blo (for 120Vline)
V3, V4 6FQ7/6CG7 Plate Fuses: BUSS BBS-2
V5-V12 EL34
V5 V7
V9 V11
V6 V8
V10 V12
V1 V2
V3 V4
MV100 Owner’s Manual 10

FUSES
LINE FUSE: The AC line is fused to protect the power transformer. This fuse will not fail in normal
operation. Failure of the fuse is a symptom of a more serious problem, so the unit should be taken to a
qualified service center. IN NO EVENT SHOULD THE FUSE BE REPLACED WITH A FUSE OF
DIFFERENT TYPE OR RATING THAN THAT SUPPLIED BY THE FACTORY.
PLATE FUSE: Your MV100 has been fitted with plate supply fuses which are designed to protect the
amplifier circuitry in the event of output tube failure. The fuse holders are physically located near the
speaker connectors. The cap unscrews counter clockwise to remove the fuse ( a BUSS BBS-2). An LED
near the fuse holder will light when the fuse is blown.
What happens when the plate fuse blows? If one of these fuses should blow, it usually indicates a
marginal EL34 tube (one of four for each channel) and an attempt should be made to identify and replace
it, by either (a) replacing the fuse and turning on the amp while watching the EL34s carefully; if a bright
white or blue flash is seen inside the tube, you’ve got the culprit. If nothing happens, then (b) lightly tap
the EL34s one by one with the plastic handle of a screwdriver while watching for flashes inside the tube.
If all efforts to identify the bad tube fail, the best course of action is to replace all tubes in the channel
thatblewthefuse.Ifthetubesareovertwoyearsold,orhavemorethan1,500hoursonthem,acomplete
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.
TOAVOID SHOCK, ALWAYSTURN OFF THE AMPLIFIER BEFOREREMOVING THE FUSEHOLDER
CAP.
Replacement fuses and tubes are available from conrad-johnson dealers.
MV100 Owner’s Manual 11

SPECIFICATIONS:
Power: 90 watts per channel RMS both channels driven into 8 ohms from 20Hz to 20KHz at no
more than 1% total harmonic distortion or intermodulation distortion.
Sensitivity: 875mv to full power.
Small Siganal Distortion: Less than .05% at midband
Phase: Phase correct (non-inverting)
Frequency response: 20Hz to 20KHz +0, -.5dB
Hum and noise: 96dB below full power output.
Input impedance: 100K ohms.
Dimensions: 20.5D x 19W x 9H inches.
Weight: 80 lbs.
MV100 Owner’s Manual 12

SERVICE
In the event your conrad-johnson MV100 stereo amplifier requires service, repack it with the original
packing material and ship via truck freight to:
Service Department
conrad-johnson design, inc.
2733 Merrilee Drive
Fairfax, VA 22031
Be sure to enclose a note explaining the problem you are having in as much detail as possible. If the
problem is intermittent, please indicate. If you do not have the original packing material, replacements
are available from conrad-johnson design at a nominal charge. If the unit is under warranty, be sure to
enclose a copy of your receipt as proof of purchase.
MV100 Owner’s Manual 13