Conrad-Johnson PV8 User manual

OWNER’S MANUAL
PV8
VACUUM TUBE PREAMPLIFIER
conrad-johnson design, inc.
703-698-8581

Congratulations on your purchase of the conrad-johnson model PV8 vacuum tube preamplifier. In it, you
have acquired one of the finest pieces of musical reproduction equipment available today. It is the result
of a decade of research by conrad-johnson design into the application of vacuum tube devices to the
reproduction of recorded music.
ThePV8wasdesignedtoprovideaudiophileswithareferencequalitypreamplifiercapableofaccurately
reproducing the dynamics, tonalities and textures of a live musical performance. The design and
materials have been carefully selected to yield many years of unvarying excellence.
Please take a few minutes to read this manual so that you will better understand the features and
capabilities of your PV8. NOTE THAT THE PV8 LINE STAGE IS PHASE INVERTING. See the section
entitled "Getting The Most From Your Pv8" for details on correct hookup to your system.
PV8 Owner’s Manual 1

LIMITED WARRANTY FOR THE conrad-johnson PV8
1. conrad-johnson design, inc. warrants to the original purchaser that the conrad-johnson PV8 will
performtospecificationsaspublishedin theowner’smanualandthatitwillbefree ofdefects in materials
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. Theabove warranty maybe transferred tosubsequent owners providedthat the warrantyregistration
card has been returned to conrad-johnson design, inc. within 30 days of the original purchase and that
theregistered owner provides thefactory with a signednotice giving the new owner’s name andaddress
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
limitation of incidental or consequential damages, or limitations on how long an implied warranty lasts,
so the above limitations or exclusions may not apply to you.
5. Thiswarranty gives you specific legal rights, and you may also have other rights which varyfrom state
to state. Questions about warranty service should be addressed to:
Service Department
conrad-johnson design, inc.
2733 Merrilee Drive
Fairfax, VA 22031
PV8 Owner’s Manual 2

REGISTERING THE WARRANTY
Please return the enclosed card to the factory within 30 days of purchase to register the warranty. The
warrantymaybetransferredtoanewownerif it has been properly registered initially and ifthe registered
ownersendsasignednoticeprovidingthe name and address of the new owner and themodelandserial
number of the unit.
Proper registration of the warranty is important! Not only will it preserve transferability of your warranty,
it will also 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.
PV8 Owner’s Manual 3

INSTALLATION
Because of the number and type of vacuum tubes used, the PV8 dissipates a significant amount of
heat (approximately 35 watts). 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 three inches of clearance should be provided above the unit and the cabinet or
shelf should be open at the back. Vertical installation is not recommended.
To minimize hum pickup, keep the unit well away from the power amplifier, and route power cords
away from input cables.
The PV8 requires an ac power line providing between 108 and 125 volts at 50 to 60 Hz. Alternatively,
the PV8 can be reconnected internally for operation on 220 volt power lines. Consult your dealer for
details about the conversion.
PV8 Owner’s Manual 4

CONNECTION
Phono input:Thisinputprovides theamplificationandequalizationrequiredbymovingmagnet andhigh
output moving coil cartridges. The input impedance is the industry standard 47,000 ohms shunted by
approximately 100 picofarads capacitance. This is well suited to nearly all moving magnet and many
high- output moving coil cartridges. If necessary, the input impedance can be lowered by soldering a
resistor across ( from center pin to ground) the input jack. To achieve a desired input resistance of RD,
use the following formula to compute the required additional resistance RA:
RA = 47000*RD/(47000-RD)
Some moving magnet cartridges require higher capacitance for optimum performance. Increasing the
input capacitance may be achieved by soldering a suitable value capacitor across the phono input jack.
Use polystyrene capacitors for this purpose.
Tuner, cd, tape 1, tape 2: These are high level inputs and are electrically equivalent. They present a
50k ohm load to the source. The outputs of your tape recorders should be connected to tape 1 andtape
2.
Recordoutput:Thetwo pairsofrecordoutputsconnecttheselectedsignaltoyourrecordersorexternal
processing loop (eg. equalizer). The output signal is not affected by the level control. Connect "record
out" to the inputs of your tape recorders or external processors.
Output 1, Output 2: Connect this output to the input of your amplifier(or crossover in a bi-amped
system). We recommend the use of an amplifier with an input impedance of 10k ohms or higher. Since
the PV8 inverts phase, it may be necessary to invert the speaker leads to maintain correct phase. See
the section on "Getting the most out of your PV8" for an explanation of this.
PV8 Owner’s Manual 5

USE OF EXTERNAL TONE CONTROLS OR OTHER EXTERNAL
SIGNAL PROCESSING DEVICES:
Use Tape 1 and Record 1 for your tape recorder, as described in the preceding two paragraphs.Connect
the output of the tone controls to Tape 2 and the input of the tone controls to Record 2. The Monitor 2
position of the monitor switch will insert the tone controls in the circuit; the Source position will provide
flat, unprocessed response. This method of connection will permit the use of tone controls with tape
playback by selecting Tape 1 in conjunction with Monitor 2.
AC OUTLETS
Four AC outlets are provided for your convenience: two, marked unswitched, are always live; the
remainingtwo are switched bythepreamp’spowerswitch. THE TOTAL CURRENTREQUIREDOFTHE
SWITCHED OUTLETS MUST NOT EXCEED 5 AMPERES. This precludes the use of these outlets for
high powered amplifiers. It is preferable not to switch power amplifiers by the preamplifier power switch
in any case.
PV8 Owner’s Manual 6

CONTROLS
OFF,POWER: Because of the delayed warmup characteristics of vacuum tube equipment, a time delay
muting circcuit is incorporated in this preamplifier. Output 1 and Output 2 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 the outputs again immediately at turn off or in the event of any power line interruption.
SELECTOR: PHONO, TUNER, CD, TAPE 1, TAPE 2: This selector switch is used to choose an input.
Theselected source will be availableat the source position of the tape monitor switch and at both record
outputs. Note that a tape deck output is fed back to its own record input- CARE MUST BE TAKEN NOT
TO SELECT TAPE 1 OR TAPE 2 WHILE THE TAPE DECK IN QUESTION IS IN RECORD MODE.
Similarly, if tape loop 1 is used for an external signal processor, Tape 1 should never be selected (and,
of course, there is no reason to select it since the external processor is not itself a program source).
Failure to observe these precautions will create an unstable feedback system and may generate a
"howling" sound.
TAPE 1, TAPE 2, SOURCE, MONITOR: Tape monitoring is accomplished via two pushbutton controls.
The first, labeled Tape1/Tape 2 selects the tape deck from which you will be monitoring. The second,
labeledSource/Monitor letsyou comparethe originalprogramsource withthe playbackfrom the chosen
tape deck. These controls permit the user to listen to a tape from one deck while recording material from
Phono, Tuner or CD inputs on a second tape deck.
MODE: LEFT, RIGHT, STEREO, REV, MONO: The setting of this switch does not alter the signal at the
record outputs except in the mono position.
Left-Passes the left channel input to both channel outputs.
Right-Passes the right channel input to both channel outputs.
Stereo-Normal stereo operation.
Reverse-Passes the left channel input to right channel output and vice-versa.
Mono-Passes the sum of left and right inputs to both channel outputs. This position produces
a near mono signal at the record outputs.
BALANCE: This control is an eleven position stepped attenuator, adjusting the channel balance in
approximately 1.5 dB steps. The maximum attenuation is about 7.5 dB, so both channels will bepresent
even in the extreme positions. In normal use the control will be centered.
LEVEL: The PV8 volume control is an extremely precise control, maintaining channel to channel
accuracy to within 1/2 dB throughout its rotation.
PV8 Owner’s Manual 7

VACUUM TUBE REPLACEMENT
The audio circuit of the PV8 uses six vacuum tubes of three different types: two 12AX7 (V1 and V2), two
5751 (V3 and V5) and two 5965 (V4 and V6). Each type has been carefully chosen for its circuit
application. It is well known that tubes of a given type vary sonically depending on the manufacturer. We
have chosen the brands of tubes we supply based on extensive auditioning of available brands. The
choice of brands has been made solely on the basis of sonic performance without regard for either cost
or prestige. We know of no vacuum tubes available which will improve the sonic performance of your
PV8. Also, the tubes in your preamplifier have been tempered by a controlled burn in procedure that
permits them to perform for a greatly extended period without sonic degradation. We anticipate two or
three years of operation 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.
Please note: The indiscriminate substitution of type 12AX7 tubes for the 5751s will seriously degrade
the sonic performance of the unit. Substitution of 12AX7 type for the type 5965 is likely to damage the
12AX7. Type 12AT7 or ECC81 may be substituted for the 5965s with only a subtle degradation in
performance.
PV8 Owner’s Manual 8

TUBE LOCATIONS
TUBE COMPLEMENT:
V1, V2 12AX7
V3, V5 5751
V4, V6 5965
FUSE:
The AC line is fused to protect the 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.
INNOEVENT SHOULD THE FUSE BE REPLACED WITH A FUSE OF DIFFERENT TYPE OR RATING
THAN THE ONE SUPPLIED BY THE FACTORY.
100V, 120V: 3/4 amp 3AG slo-blo
220V: 1/2 amp 3AG slo-blo
GETTING THE MOST FROM YOUR PV8
The conrad-johnson PV8 offers an unparalleled level of sophistication and refinement in music repro-
duction, but it cannot transform an inferior stereo system. Only high quality amplifiers and loudspeaker
systems will be capable of fully revealing the capabilities of this precision instrument.
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:thatis,theinitialeffect isariseinpressure.Theeariscapable
of distinguishing these positive transients from the musically unnatural alternative ofanegativetransient
(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 is either
phase correct or phase inverting (including the source 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).
PV8 Owner’s Manual 9

THE PV8 IS PHASE INVERTING. If your system has an odd number of inversions, then you must add
onephase inversion. This will be the case if the PV8 is the only unit in the chain that invertsphase. 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
phaseby 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.
AC LINE POLARITY
Each piece of electronic equipment in your system is subject to minute ac leakage currents to the
chassis. Since the chassis of components in a system are usually connected via the ground side of the
interconnect wires, these leakage currents are superimposed on the musical signals. It is possible to
minimize these current flows by carefully selecting the way in which each component is plugged into the
wall outlet. Because the power cord on the PV8 is not polarized, it can be plugged in two ways. It will
normally sound better in one orientation than in the other. The same will be true of any electronic device
in your system. 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 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.
TIP
Warm up the PV8 before listening: The sonic performance of the PV8 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 several minutes.
Questions: If you have questions about the installation or function of your PV8 do not hesitate to call
Customer Service at [phone].
PV8 Owner’s Manual 10

PV8 SPECIFICATIONS
Gain: Phono stage 47dB
High level 31dB
Output: Maximum 20V, rated at 2.5V
Phase: Line stage inverts phase of all inputs.
Phono overload: in excess of 200 mv at 1KHz
Response: bandpass 2Hz to more than 100 KHz
RIAA equalization to + .25dB (20Hz-20KHz)
Hum and noise(20Hz-20KHz):
phono inputs:74dB below 10mv input
Line level:84dB below 2.5V output
Distortion:
THD less than .25%
IM less than .25%
Ouput impedance: less than 200 ohms
Dimensions: 19"W x 3.5"H x 12.5"D
Weight: 12 lbs.
PV8 Owner’s Manual 11

SERVICE
In the event your conrad-johnson PV8 stereo preamplifier requires service,repack it with the original
packing material and ship via United Parcel Service (UPS) to:
Service Department
conrad-johnson design, inc.
2733 Merrilee Drive
Fairfax, VA 22031
Be sure to include a copy of your sales receipt from the original purchase, along with 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
for a nominal charge.
PV8 Owner’s Manual 12