Conrad-johnson design PV 7 User manual

OWNER'S MANUAL
PV 7
VACUUM TUBE PREAMPLIFIER
conrod-johnson design, inc.
703-698-8581

Thank you for purchasing the conrad-johnson model PV7 vacuum tube preamplifier.
We believe that it will be one of the most satisfying purchases of audio equipment
that you will make.
The PV7 was designed to provide audiophiles with a moderately priced preamplifier
of high quality which would accurately reproduce 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
use of your PV7.

LIMITED WARRANTY FOR THE conrad-johnson PV7
1. conrad-johnson design, inc. warrants to the original purchaser that the conrad-
johnson PV7 will perform to specifications as published in the owner's manual
and that it will be free of defects 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. 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 limitation of incidental or
consequential damages, 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:
conrad-johnson design, inc.
2733 Merrilee Drive
Fairfax Virginia 22031
703-698-8581

ABOUT conrad-johnson design
Conrad-Johnson Design offers exclusively audiophile audio components. We believe
that our commitment to the purchaser of our products is nearly unique in the industry.
The services we offer to conrad-johnson owners include:
•Information - Registered owners of conrad-johnson equipment will be directly
informed of new equipment we have to offer. They will also be informed of any
significant changes in the design of their equipment resulting from our ongoing
development program.
•Factory updating - Should significant design changes be made, conrad-johnson
design will, whenever practical, offer to update existing equipment. This service
will be offered at a minimal charge to cover parts, labor, and handling.
•Factory service - Any conrad-johnson product may be returned to the factory for
service. All equipment serviced at the factory will perform to its published
specifications when returned. Factory service will be offered at reasonable rates.
•Transferable warranty - conrad-johnson design guarantees its products, not the
owner. Should you decide to sell the product, the warranty may be transferred to
the new owner. (See Registering the Warranty).
REGISTERING THE WARRANTY
Please return the enclosed card to the factory within 30 days of purchase to register
the warranty. The warranty may be transferred to a new owner if it has been properly
registered initially and if the registered owner sends a signed notice providing the
name and address of the new owner and the model and serial 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.

CIRCUIT DESIGN
The phono stage of the PV7 consists of two cascaded triode amplifiers direct coupled
to a cathode follower for low output impedance. Phono equalization is accomplished
by R-C networks in a direct coupled feedback loop driven by the cathode follower.
The RIAA components are 1% tolerance, with RIAA capacitors being polystyrene
dielectric. The audio circuitry is executed entirely with precision, low noise metal
film resistors. All coupling capacitors are polypropylene dielectric. The line stage
consists of a single voltage amplifier direct coupled to a cathode follower with an
overall feedback loop.
Plate voltage is supplied by a sophisticated, low impedance voltage regulator. The
regulator's output supplies the audio circuitry directly to minimize power supply
source impedance. The regulator is designed using solely polypropylene capacitors,
isolating the audio circuitry from the non-linear effects of electrolytic capacitors.
Filaments are operated on a regulated d.c. voltage to minimize noise at the low signal
levels in a preamplifier and to prevent line voltage fluctuations from coupling
infrasonic disturbances to the audio signal.

INSTALLATION
Because of the number and type of vacuum tubes used, the PV7 dissipates a
significant amount of heat (approximately 30 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 recommend.
To minimize hum pickup, keep the unit well away from the power amplifier, and
route power cords away from input cables.
THE PV7 IS TO BE OPERATED ONLY ON AC LINE VOLTAGE OF 108 to 125
VOLTS, 50 or 60 HZ
In any system of audio electronics minute leakage currents from the ac line
transformers will flow in the signal ground connections between preamplifier and
amplifier. These currents can intermodulate with the signal and affect the clarity of
sound. Generally, one orientation of the line cord will provide much lower current
flows. When combined with the finest associated equipment this effect is clearly
audible with the PV7. After installing the unit try reversing the line cord at the wall
outlet to pick the most satisfactory orientation.

CONNECTION
Inputs:
Phono - The phono inputs provide the additional amplification and RIAA
equalization required by most high fidelity cartridges. The input impedance is 47,000
ohms shunted by approximately 140 picofarads capacitance. This is the industry
standard load and will work well with most moving magnet cartridges and all pre-
preamplifiers for moving coil cartridges. A few moving magnet cartridges perform
better with a 10,000 ohm load which may be achieved by having a service technician
shunt the phono inputs with 12,000 ohm resistors.
For some moving magnet cartridges, optimum performance requires higher
capacitive loads. This may be achieved by soldering suitable value capacitors across
the phono input jacks. Polystyrene capacitors are recommended for this purpose.
Tuner, Auxiliary, Tape 1 Tape 2 - These are all high level inputs and are
electronically equivalent. The outputs of your tape recorders should be connected to
Tape 1 and Tape 2.
Outputs:
Record 1, Record 2 - Connect these to the inputs of your tape recorders.
Output 1 Output 2 - Connect to the inputs of amplifiers with impedance of l0k-ohms
or greater.
AC OUTLETS
Two ac outlets are provided for your convenience: they are unswitched (always live).
THE TOTAL CURRENT REQUIRED OF THE OUTLETS MUST NOT EXCEED
5 AMPERES. This precludes the use of these outlets for high powered amplifiers.

OPERATION
Turn on: Because of the delayed warm up characteristics of vacuum tube equipment,
a time delay muting circuit is incorporated in this preamplifier. Output 1 and Output
2 are grounded via a relay for approximately 45 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: Use the selector switch to.choose an input from Phono, Tuner, Tape l, Tape
2 or Auxiliary inputs. The selected source will be available at the source (out)
position of the tape monitor switch and at both Record Outputs. Note that dubbing
between tape decks is possible in both directions. Also, since the selected decks'
output is fed back to its own record input, care must be taken not to select a tape deck
which is in the record mode. Similarly, if one of the tape loops is used for an external
signal processor, that tape loop 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.
Monitor: This switch permits you to compare source and tape while recording on
either or both tape decks from the selected input. You may wish to use Tape 2 and
Record 2 to install an external signal processor such as graphic tone controls. Then,
the Tape 2 position will choose the processed signal while Source will choose the
pure signal.
Balance: Permits continous control of location of stereo image from left to right. In
the full counterclockwise position only the left channel will be heard. Similarly, the
full clockwise position will reproduce only the right channel. In normal use this
control will be centered.
Volume: The PV7 volume control Is an extremely precise control, maintaining
channel to channel tracking within t 1/2 db throughout its rotation.

VACUUM TUBES
The audio circuit of the PV7 uses five vacuum tubes of two different types: three
12AX7 (V1, V2 and V4) and two 12AT7 (V3 and V5). 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
that we supply based on extensive auditioning of available brands. The choice of
brand has been made solely on the basis of sonic performance without regard to
either cost or prestige. We know of no vacuum tubes available of the specified types
which will improve the sonic performance of your PV7. 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 to 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: Substitution of 12AX7 type for the type 12AT7 is likely to damage the
12AX7. Other tube type substitutions may damage the preamp circuitry or
transformer.

TUBE LOCATIONS:
Tube complement:
V1,V2,V4: 12AX7
V3,V5: 12AT7
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. IN NO EVENT SHOULD THE FUSE
BE REPLACED WITH A FUSE OF DIFFERENT TYPE OR RATING THAN
THAT SUPPLIED BY THE FACTORY.
V1
V2 V4
V5
V3

SPECIFICATIONS
Gain: phono stage 40 db
high level 20 db
Output:maximum 25v (rated at 2.5v)
Phase: phono is non-inverting so tape outputs are phase correct
high level stage inverts phase of all inputs including phono
Phono overload: in excess of 500mv at 1KHz
Response: bandpass 2Hz to more than 100 KHz
RIAA equalization to +/- .25db (20-20KHz)
Total hum and noise (20-20KHz):
Phono inputs 72db below 10mv input
High Level: 84db below 2.5 volt output
Distortion: THD less than .1%
IM less than .1%
Output impedance: Less than 200 ohms
Dimensions: 14 1/2 x 3 3/4 x 10"
Weight: 12 1/4 lbs.

SERVICE
In the event your conrad-johnson component requires service, repack it with the
original packing material and ship it to:
Service Department
conrad-johnson design, inc.
2733 Merrilee Drive
Fairfax, VA 22031
For components weighing 90 lbs. or less, we recommend that you ship via United
Parcel Service (UPS). In all cases, be sure to adequately insure your component. 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, enclose a copy of your receipt as proof
of purchase.