Conrad-Johnson CAV50 User manual

Thankyouforselecting theCAV50 asthe controlamplifier foryour audio
system. The first control amplifier (integrated amplifier) from conrad-
johnson, the CAV50 benefits from more than two decades of building
among the finest audio amplifiers and preamplifiers in the world. It
demonstrates the same remarkable ability to recreate the dynamics,
textures, tonalities, and ambience of live musical performances for
which conrad-johnson products are known. With the CAV50, we believe
that you will experience the excitement of discovery in hearing more
from your favorite recordings than ever before.
Atconrad-johnson, weexpect ourproducts tobe asource ofsatisfaction
and 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 CAV50 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 CAV50, and to
provide any needed service both during, and after the warranty period.
Our goal is to heighten your enjoyment of recorded music.
CAV50 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.
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
CAV50 Owner’s Manual 2

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 Service Department can also be reached 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.
CAV50 Owner’s Manual 3

Circuit Design
The CAV50 circuit is notable for its elegant simplicity. A passive control
unit selects among inputs, and sets the signal level. The selected signal
is routed to a triode input amplifier comprised of paralleled sections of a
12AX7A which 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 features ultralinear
operation of a pair of EL34s, which permits relatively high power 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 of massive polypropylene capacitors
enablestheCAV50 toeasily meettheseextraordinary currentdemands.
A single stage triode amplifier provides gain and a buffered preamp
output for use with a secondary amplifier or powered subwoofer.
Voltageregulators forthe voltageamplifiersandphaseinvertersprovide
nearly absolute isolation of these sensitive stages from the output
stages.
Optionally, the CAV50 may be reconnected internally for triode opera-
tion of the output stage, for exceptionally musical performance, but at
considerably reduced output power. The conversion is simple, but does
require soldering. Consult your dealer as to which configuration will
perform best in your system.
CAV50 Owner’s Manual 4

Installation
As is the case with any vacuum-tube power amplifier, the CAV50
dissipates a significant amount of heat. Provision must be made for
adequate 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
onthesides.Thecabinet orshelf shouldbeopen atboth frontandback.
For more restricted installations, cooling fans are essential.
The CAV50 is supplied with a cover for the vacuum-tubes, which can be
secured by the four 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 CAV50s 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 CAV50 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 CAV50 to
minimize it’s susceptibility to radio frequency interference and other
forms of EMI. Choice of materials, physical layout, grounding practice,
andpowersupply designhaveall beenspecifiedwith a viewto 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
theexpenseof degradedaudioperformance. Wefindthat the approach
we have taken has worked extremely well, resulting in only rare in-
stances 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.
CAV50 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
PH/AUX1, TUNER, CD, VIDEO, AUX2, EPL IN: These are high level
inputs and are electrically equivalent. They present a 50k ohm load to
the source. EPL stands for "external processor loop". If used, the
outputsof a tape recorder or external processor (eg. equalizer) should
be connected to "EPL IN".
EPL OUT: This output connects the selected signal to your recorder or
external processor. The output signal is not affected by the level control.
Connect "EPL OUT" to the inputs of your tape recorder or external
processor.
PRE OUT: Connect this output to the input of a secondary amplifier, or
crossover, or powered subwoofer in a bi-amped system. We recom-
mend the use of an amplifier with an input impedance of 50k ohms or
higher. Since the pre out of the CAV50 inverts phase, it may be neces-
sary to invert the speaker leads to maintain correct phase. See the
section on "Getting the most out of your CAV50" for an explanation of
this.
EXTERNAL TONE CONTROLS OR OTHER SIGNAL PROCESSING
DEVICES: Connect the output from your processor to the EPL IN input,
and the input of your processor to the EPL OUT output on the CAV50.
Depressing the EPL switch to the "in" position will insert the processor
into the circuit; releasing it to the "out" position will provide flat, unproc-
essed response.
CAV50 Owner’s Manual 6

RIGHT, LEFT: Binding posts are provided for connection of your loud-
speakers. 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.
CAV50 Owner’s Manual 7

Controls
power: This switch turns the amplifier on and off. Because of the
delayed warmup characteristics of vacuum tube equipment, a time
delay muting circuit is incorporated in the CAV50 to mute the preampli-
fier output (PRE OUT) at turn-on and turn-off. The PRE OUT connec-
tions are grounded via a relay for approximately 90 seconds after the
unit is turned on in order to suppress warm-up transient noises. The
relay grounds these outputs again immediately at turn off or in the event
of any power line interruption.
selector: ThisswitchisusedtochooseamongAUX1/PHONO,TUNER,
CD, VIDEO, and AUX2 inputs. The selected source is routed to the EPL
OUTconnection. Whenthe EPLswitchisintheout(source)positionthe
selected source will also be sent to the PRE OUT connections, and to
the speaker (RIGHT and LEFT) connections.
epl: Tape monitoring, and selection of an external processor is accom-
plished via a pushbutton control. The button, labeled epl, when de-
pressed selects your tape deck or external processor as an input
source.
volume: The CAV50 volume control is a precise control, maintaining
channel to channel accuracy to within 1 dB throughout most of its
rotation.
CAV50 Owner’s Manual 8

Getting The Most From Your CAV50
When combined with comparably high quality source (such as the
conrad-johnson DV2b cd player) and speakers, the CAV50 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 speaker outputs (RIGHT and LEFT) of the CAV50 are phase
correct.
The preamplifier outputs of the CAV50 are phase inverting. If this part
of your system has an odd number of inversions (as will be the case if
the CAV50 preamplifier section is the only inverting component), then
you must add one phase inversion in this part of the system. This is
conveniently done by reversing the positive and negative connections
to the speakers or subwoofers connected through the PRE OUT path
(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
CAV50 Owner’s Manual 9

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.
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
yourCAV50do not hesitatetocall Customer Serviceat(703) 698-8581.
CAV50 Owner’s Manual 10

Tube Replacements
The CAV50 uses nine vacuum tubes of four different types: two 12AX7A
(V1 and V2), two 6SN7 (V3 and V4), one 12AU7 (V9) 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 CAV50. We highly recommend that you purchase replacement
tube sets from conrad- johnson design.
We anticipate tube life to accomodate two to three years of operation
without degradation in normal use - if the amplifier is switched off when
notinuse.Ifitis leftonatalltimes,tubelifecanbeexhaustedinamatter
of a few months.
The CAV50 has been designed to make tube replacement as simple as
possible.Becausethe outputtubesare individuallybiased,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 CAV50 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 plastic screwdriver
has been included with your amplifier for this purpose. After replacing
the tubes, the amplifier should be connected to a load (your loudspeak-
ers 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 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.
CAV50 Owner’s Manual 11

This biasing procedure should be performed whenever the amplifier’s
output tubes are replaced and after each six months of average use.
PLATEFUSE: YourCAV50hasbeenfittedwithplatesupplyfuseswhich
are designed to protect the amplifier circuitry in the event of output tube
failure. The fuse holders are physically located on top of the chassis
near output tubes V5 and V6. 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.
CAV50 Owner’s Manual 12

Specifications:
Power (ultralinear operation): 45 watts per channel RMS both
channels driven into 8 ohms from 30Hz to 15KHz at no more than
1% total harmonic distortion or intermodulation distortion.
Power (triode operation): 22 watts per channel RMS both
channels driven into 8 ohms from 30Hz to 15KHz at no more than
1.5% total harmonic distortion or intermodulation distortion.
Sensitivity: 500 mv to full power.
Gain to PRE OUT: 20 dB
Phase (speaker outputs): Phase correct (non-inverting)
Phase (PRE OUT): Phase inverting
Frequency response: 20Hz to 20KHz +0, -.5dB
Hum and noise: 98dB below full power output.
Hum and noise (PRE OUT): 94 dB below 2.5V output
Distortion (PRE OUT): less than .1% THD or IMD
Dimensions: 14D x 17.5W x 7.25H inches.
Weight: 44 lbs.
Internal Fuses
The CAV50 power transformer is protected by a fuse on the ac power
line (F1) and by a seperate fuse (F2) for the secondary windings for the
filament supply. Both fuses are located on the printed circuit board
inside the chassis. A failure of either of these fuses is a symptom of a
more serious problem, and a competent service technician should be
consulted. Inno eventshould fusesbe replacedwith avalue ortype
different than that originally supplied. The correct fuse values and
types are:
F1: 5 amp, slow blow If configured for 100 or 120V:
3 amp, slow blow if configured for 220 or 240V.
F2: 4 amp, slow blow
CAV50 Owner’s Manual 13