Conrad-johnson design MV60 User manual

Thank you for selecting the MV60 to power your audio system. The
MV60 draws on two 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 the dynamics, textures, tonalities, and
ambience of live musical performances. With the MV60, we believe that
you will experience the excitement of discovery in hearing more from
your favorite recordings than ever before.
Atconrad-johnson,weexpectourproductstobeasourceofsatisfaction
and of pride to their owners for many years to come. Accordingly, circuit
designs, parts and materials for all conrad-johnson products are se-
lected with a view to maintaining optimal performance over the years.
Our reputation for producing among the industry’s most reliable compo-
nents is a natural consequence of this engineering approach.
Although operation of the MV60 is quite straightforward, please take a
few minutes to read this manual for useful information on it’s installation
and operation.
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 MV60, and to
provide any needed service both during, and after the warranty period.
Our goal is to heighten your enjoyment of recorded music.
MV60 Owner’s Manual 1

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 pur-
chaser, 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 excep-
tion of vacuum tubes 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 par-
ticular 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.
MV60 Owner’s Manual 2

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 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 email
at [email protected], 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 ob-
tainedfromourservicedepartmentforanominalchargeifyounolonger
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 your approval before commencing service.
Registering The Warranty
Please return the enclosed card to the factory within 30 days of pur-
chase to register the warranty.
MV60 Owner’s Manual 3

CIRCUIT DESIGN
The MV60 circuit is notable for its elegant simplicity. A triode input
amplifiercomprisedofparalleledsectionsofa 12AX7A is direct coupled
to a cathode coupled differential phase inverter using high current
triodesto provide balanced, lowimpedance drive to thepush-pull output
stage.The output stagefeatures ultralinear operationof a pairof EL34s,
which permits high power levels while greatly reducing the source
impedanceofthe stage. As a result, theamplifieriscapableofsupplying
the large current demands of high amplitude musical transients driven
intoreactive speakerloads. A substantial main power supply ofmassive
polypropylene capacitors enables the MV60 to easily meet these ex-
traordinary current demands. Voltage regulators for the voltage amplifi-
ers and phase inverters provide nearly absolute isolation of these
sensitive stages from the output stages.
Optionally, the MV60 may be reconnected internally for triode operation
of the output stage, for exceptionally musical performance, but at con-
siderably reduced output power. The conversion is simple, but does
require soldering. Consult your dealer as to which configuration will
perform best in your system.
MV60 Owner’s Manual 4

INSTALLATION
As is the case with any vacuum-tube power amplifier, the MV60 dissi-
pates a significant amount of heat. Provision must be made for ade-
quate ventilation. Mount the unit on a flat, hard surface, taking care that
the ventilation holes in the bottom are unobstructed. Maintain at least
four inches of clearance above the unit, and at least three inches on
the sides. The cabinet or shelf should be open at both front and back.
For more restricted installations, cooling fans are essential.
The MV60 is supplied with a cover for the vacuum-tubes, which can be
secured by the two captive screws inside the cover. The cover provides
protection from the hot surfaces of the vacuum-tubes. It should always
be used in installations where there is any possibility that children or
pets may come near the amplifier.
All MV60s 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 MV60 will have the correct operating voltage and fre-
quency 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 MV60 to mini-
mizeit’s susceptibilityto radio frequency interference and other formsof
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
notto compromise thisobjectivebytheapplicationof 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 compro-
mising the performance of our product in the 99.9% of installations
where EMI is not a problem.
MV60 Owner’s Manual 5

CareininstallationcanoftenavoidEMIinducedproblems.Thefollowing
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).
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: Connectthe preamplifier toyour MV60 amplifierat the RCAtype
connectors located on the back of the amplifier.
OUTPUT: Five way binding posts are provided for connection of your
loudspeakers, with correct spacing to accept a standard "double ba-
nana" plug. They will also accept spade lugs, bare wire, or pin connec-
tors. The two channels should be connected in correct "relative phase".
This means that when the same signal 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 a recording of a solo vocalist (use a mono recording if avail-
able). 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.
MV60 Owner’s Manual 6

Getting The Most From Your MV60
In a system of commensurate high quality components, the conrad-
johnson MV60 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 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 almost exclu-
sively 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 pres-
sure). 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 MV60 is phase correct. If your system has an odd number of
inversions,thenyoumustaddonephase inversion. This is conveniently
done by reversing the positive and negative connections to your speak-
ers (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.
MV60 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 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 spe-
cific system.
Questions: If you have questions about the installation or function of
your MV60 do not hesitate to call Customer Service at [phone].
MV60 Owner’s Manual 8

TUBE REPLACEMENTS
The MV60 uses eight vacuum tubes of three different types: two
12AX7A (V1 and V2), two 6SN7 (V3 and V4) and four EL34s (V5
through V8). 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 MV60. 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 amplifier is switched off when
notinuse.Ifitisleftonatalltimes, tubelifecanbeexhaustedinamatter
of a few months.
The MV60 has been designed to make tube replacement as simple as
possible.Because the output tubesare individually biased, replacement
tubes need not be matched pairs. No a-c balance adjustment is neces-
sary. It is necessary to re-bias the amplifier when the output tubes are
replaced. The MV60 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 screw-
driver has been included with your amplifier for this purpose. After
replacing the tubes, the amplifier should be connected to a load (your
loudspeakerswillworkfine)and there should be nosignal appliedto 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 four screwdriver adjustable controls 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
further 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.
MV60 Owner’s Manual 9

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 MV60 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 con-
nectors. The cap unscrews counter clockwise to remove the fuse (a
BUSS BBS-3/4). An LED near the fuse holder will light when the fuse is
blown.
What happens when the fuse blows? If one of these fuses should blow,
it usually indicates a marginal output tube (one of two 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 output
tubes carefully; look for a bright white or blue flash inside the tube. If
nothing happens, then (b) lightly tap the output tubes one by one with
the plastic handle of a screwdriver while watching for flashes inside the
tube. If efforts to identify the bad tube fail, the best course of action is to
replacebothtubesinthechannelthatblewthefuse.Ifthetubesareover
two years old, or 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.
MV60 Owner’s Manual 10

SPECIFICATIONS:
Power (ultralinear operation): 55 watts per channel RMS both chan-
nels driven into 4 ohms from 30Hz to 15KHz at no more than 1% total
harmonic distortion or intermodulation distortion (can be re-connected
internally for 8 or 16 ohm loads).
Power (triode operation): 25 watts per channel RMS both channels
driven into 4 ohms from 30Hz to 15KHz at no more than 1.5% total
harmonic distortion or intermodulation distortion.
Sensitivity: 820 mv to full power.
Phase: Phase correct (non-inverting)
Frequency response: 20Hz to 20KHz +0, -.5dB
Hum and noise: 95dB below full power output.
Input impedance: 100K ohms.
Dimensions: 13.25D x 17.625W x 7H inches.
Weight: 48 lbs.
Internal Fuses
The MV60 power transformer is protected by a fuse on the ac power line
(F1, located in a compartment in the ac line-cord receptacle mounted
on the back of the amplifier), and by a separate fuse (F2, located on the
pc board) for the secondary windings for the filament supply. A failure of
either of these fuses is a symptom of a more serious problem, and a
competent service technician should be consulted. In no event should
fuses be replaced with a value or type different than that originally
supplied. The correct fuse values and types are:
F1: 5x20mm 5 amp T-type if configured for 100 or 120V:
5x20mm 3 amp T-type if configured for 220 or 240V.
F2: 3AG 4 amp, slow blow
MV60 Owner’s Manual 11