Herron Audio VTPH-2 User manual

Vacuum Tube
Phono Preamplifier
Vacuum Tube
Phono Preamplifier
Owner’s Manual
VTPH-2
VTPH-2

Thank you for your investment in
the Herron Audio Vacuum Tube
Phono Preamplifier, a masterpiece
of high-precision analog audio
playback equipment. It is designed
to be the finest product of its type
available. The care in engineering
and manufacturing of this product
anticipates a lifetime of musical
enjoyment.
The Herron VTPH-2 Phono
Preamplifier was created to address
the retrieval of musical information
from vinyl LPs without compromise.
The original design (the VTPH-1)
was originally only intended for use
by a few dedicated music lovers in
their cutting edge audio systems.
The design was so good and demand
so high that the unit was refined
and engineered with the additional
features and performance enhance-
ments which are incorporated in
the VTPH-2. In the process, impor-
tant discoveries were made about
tolerances and the threshold of
human hearing limits.
The VTPH-2 is a significant step
forward in the art and science of
phono preamplification. Its dynam-
ics and startling transparency may
be difficult to describe, but are not
difficult to hear. Expect to discover
new joy from every record in your
collection.
At Herron Audio, our goal has
always been to reproduce, as
faithfully as possible, the musical
experience captured on each of your
cherished recordings. Nothing
removed, and—equally important—
nothing added. Meticulous design,
painstaking selection of component
parts, and the evolution of our
experience help us get closer to
that target with each new model.
This product is engineered to
be user friendly and overcomes the
fears that many have expressed con-
cerning the use of vacuum tubes in
their systems. Its limited production
ensures that the components in each
unit are matched to the highest stan-
dards in the industry. Manufacturing
of the unit is performed under the
tightest of quality controls. Compo-
nents are hand-matched to exacting
standards—to ensure identical unit-
to-unit performance. For example,
capacitors in the RIAA equalization
stage are hand matched to tolerances
of better than 0.1%. The units are
burned in, bench tested, and hand-
matched to the original design.
Owner’s Manual
three
Please read the Owner’s Manual completely BEFORE operating the unit.
VTPH-2 Herron Audio Vacuum Tube Phono Preamplifier
two
Table of Contents
3Introduction
5Design Considerations
6Front Panel Information
7Rear Panel Information
8Installation and Operation
9Cartridge Loading
10 Power Line Polarity
10 Optimum Performance
10 Changing Tubes
11 Tube Locations
11 Tube Recommendatons
12 Technical Specifications
© 2007 Herron Audio
Division of Herron Engineering, Inc.
12685 Dorsett Road
#138
St. Louis, MO 63043
314.434.5416
314.434.6629 fax
Welcome!
Welcome!

Design Considerations
• Two operating modes: Moving Coil and Moving Magnet
• Separate RCA input connectors for Moving Coil and Moving
Magnet inputs
• Additional RCA connectors for external Moving Coil loading
• Moving Coil/Moving Magnet mode switch
• 15 second mute during mode change
• Cartridge bias Moving Coil input stage allows for infinite load
resistance (operation with cartridge unloaded)
• All-tube signal path (moving magnet mode)
• Passive RIAA equalization for accurate phase and amplitude response
• Available in two factory set tube configurations
• Class A operation
• Star grounding for low interference susceptibility and clean signal path
• Zero feedback—no feedback loops in the audio circuitry
• Low noise
• High input signal capacity without overload; see technical specifications
• Gold plated RCA and ground connectors
• Audio path capacitors are high quality metal film
• Hand-picked components for accurate response
• Automatic muting at startup and shutdown
• 78,000
 F of power supply energy storage capacitance
• 4 levels of high voltage regulation
• Regulated soft-start DC filament supply
• Regulated tube bias supply
• Toroidal power transformer
• Reversing power line (AC) polarity switch for minimizing line-to-chassis
reactive currents and noise pickup
• Controlled warm-up of tube filaments and high voltage for extended
tube life
• Low plate operating currents for extended tube life and cool operation
• Front panel indicators for power, voltage, and output (mute release)
• Each unit is given a 48-hour burn-in, including rigorous bench and
listening tests
Owner’s Manual
five
Please read the Owner’s Manual completely BEFORE operating the unit.
These techniques ensure that each
unit performs to the high standards
established in the development of
the original prototypes. This costly
process is reflected in the unprece-
dented performance and lack of
unit-to-unit variations of Herron
Audio components.
The special power supply in all
Herron Audio products reflects the
engineering innovation that allows
the Herron VTPH-2 Phono Preampli-
fier to provide the highest musical
satisfaction without the artifacts
produced by most other tube-based
components. This power supply
provides a rigid voltage source to the
tubes, producing remarkable resolu-
tion of musical events in time and
sound stage. The circuit board layout
was engineered with all of its electri-
cal properties considered in order
to achieve fine audio performance
with greater consistency than hand
wiring. Compromise was not an
option. The unique design of the
Herron VTPH-2 Phono Preamplifier,
along with its conservative design
and operating parameters means
that owners can expect the indus-
try’s highest level of performance
to be maintained over the extended
life of the unit.
Operating the Herron VTPH-2
Phono Preamplifier is easy and
straightforward. The unit has been
designed to be exquisitely simple
and user friendly, with its opera-
tional readiness easily monitored.
During the manufacturing process,
every unit is subjected to a battery
of quality control checks. Each unit
is run through a full forty-eight hour
burn-in, and then measurements
are made to make sure that it is func-
tioning correctly. Last and most
importantly, careful listening tests
are made in comparison to a refer-
ence unit, to make sure each Phono
Preamplifier performs up to the
strictest Herron Audio standards.
The staff of Herron Audio are
audiophiles who regard the high-
quality reproduction of the perfor-
mance of music as one of the finest
pursuits in the engineering arts. We
at Herron Audio believe in the pursuit
of audio perfection. We hope you
enjoy the fruits of our efforts. If you
have any comments, suggestions,
or questions, please contact us at
314-434-5416.
VTPH-2 Herron Audio Vacuum Tube Phono Preamplifier
four

The Rear Features
The Rear Features
Power Switch: On / Off
AC Polarity: Allows the user to select the AC polar-
ity offering the best performance.
Used during set-up of the unit, and
whenever changes are made to the
AC source.
IEC Power Jack: Used to connect the AC power cord
to the unit.
Ground Connectors: Used to connect the phono ground
bleed wire to the unit. Connects to
the star ground system in the unit.
MC Inputs RCA Jacks: Used to connect to moving coil
cartridge.
MC Load RCA Jacks: Used to connect Male RCA plugs
with load resistors for moving coil
cartridge
Moving Coil/Moving Magnet Used to change from moving coil
Mode Switch: to moving magnet mode
MM Inputs RCA Jacks: Used to connect to moving magnet
cartridge
Outputs RCA Jacks: Used to connect the unit to a line
stage preamplifier
Owner’s Manual
seven
Please read the Owner’s Manual completely BEFORE operating the unit.
The VTPH-2 features a
1
⁄
2
inch thick
anodized aluminum front panel
with three lights for monitoring the
operational readiness of the unit.
When the VTPH-2 is powered up,
the automute feature is engaged
until the unit is ready for operation.
The first indicator on the panel is
the Power LED, which indicates the
unit has been turned on. After a few
moments, the voltage LED gradually
brightens, as the voltage to the fila-
ments slowly increases. When the
unit is ready to operate, the Output
LED illuminates and the automute
is disengaged, allowing signal to be
passed to the line stage/preamp.
This process generally takes just
more than a minute, but can take
considerably longer if the unit has
not been operated for a long period
of time. The output LED will flash
on and off during the 15 second
Moving Coil/Moving Magnet mode
change. This indicates that the unit
is muted for speaker protection.
VTPH-2 Herron Audio Vacuum Tube Phono Preamplifier
six
The Front Panel
The Front Panel

The moving coil inputs can be
loaded to a particular cartridge speci-
fication by externally connecting the
appropriate resistors using the “MC
LOAD” RCA connectors on the back
of the unit, or they can be internally
soldered at the MC INPUTS circuit
board (this should only be done by
a competent technician).
The moving coil inputs have no
load resistors installed unless speci-
fied by the customer when the unit
is ordered from Herron Audio.
We highly recommend trying the
VTPH-2 in the no load configuration
as the unit is supplied for many
moving coil cartridges. 47,000 (47k)
ohm RCA load plugs are supplied
with the unit for optional use. Addi-
tional user specified loading plugs
can also be purchased with the unit.
The moving magnet inputs are
factory loaded at 47,000 (47k) ohms,
100pF. (standard loading for moving
magnet cartridges)
Owner’s Manual
nine
Please read the Owner’s Manual completely BEFORE operating the unit.
The operation of the Herron VTPH-2 Phono Preamplifier is straightforward. As
with any fine audio component, careful set-up and integration into one’s system is
important for optimum performance, safety, and reliability. Please read through
the following set-up instructions completely prior to operating the unit.
VTPH-2 Herron Audio Vacuum Tube Phono Preamplifier
eight
Installation and Operation
Installation and Operation
Procedure
1. Position the unit in a well-
ventilated area on a firm, stable
surface, away from equipment that
generates alternating magnetic
fields such as motors, transform-
ers, etc. Magnetic fields of this
type can introduce hum into the
signal path.
2. Connect the ground bleed wire
from the turntable to the ground
connector of the VTPH-2. (this
may be needed to prevent hum at
the inputs to the VTPH-2)
3. Connect the cartridge signal leads
from the turntable (tone arm) to
the VTPH-2 left-to-left and right-
to-right and the appropriate input
connectors (“MC INPUTS” for a
moving coil cartridge or “MM
INPUTS” for a moving magnet
cartridge. (left-to-left and right-
to- right)
4. Connect the line stage preampli-
fier inputs to the “OUTPUTS”
RCA connectors on the back
of the VTPH-2 (left-to-left and
right-to-right)
5. Plug the power cord into the
VTPH-2. Make sure it is firmly
seated into the IEC socket prior
to inserting the plug into an AC
outlet.
6. Plug the power cord into a 115
volt (U.S. spec. units) AC outlet.
7. Power up the unit by switching
on the power switch.
8. Observe the LEDs for the appro-
priate operation (see the Front
Panel Indicators section). Listen
carefully for the click of the
automute engaging the outputs.
9. Power up the rest of the system
with the line stage input selector
positioned to select any input not
otherwise in use other than the
phono preamplifier. With the
volume control of the line stage
set at its lowest position, select
the phono preamplifier. Gradually
increase the volume control until
a normal listening level is
reached.
Cartridge Loading
Cartridge Loading
External MC Load
Resistor RCA Plugs
Moving coil loading RCA resistor plugs can be inserted into the back of the
VTPH-2 at the "MC Load" connectors to properly load specific moving coil
cartridges. Check with your cartridge manufacturer for recommended loading.

have time to discharge before enter-
ing the unit.
Care needs to be taken during
this procedure in order to prevent
damage by static electricity to the
VTPH-2 internal components. Use
of a grounding wrist strap is
highly recommended.
The original tubes should provide
many years of good performance,
due to the conservative plate voltage
and current operating requirements
of the Herron Audio Phono
Preamplifier.
If tube replacement is required,
channel-to-channel gain matching
can be done using the left and right
gain controls on the printed circuit
board.
Tube Locations
Tube Recommendations
Units RIAA passively compensated
for 4 12AX7s, and 1 12AT7,
the following tubes are
recommended:
V1 and V3 (first gain stage) EI 12AX7
V2 and V4 (2nd gain stage) EI 12AX7
V5 (output stage) EI 12AT7
Units RIAA passively compensated
for 2 12AX7s, and 3 12AT7s,
the following tubes are
recommended:
V1 and V3 (first gain stage)
Svetlana 12AX7
V2 and V4 (2nd gain stage)
Electro-harmonix 12AT7
V5 (output stage) EI 12AT7
Other current production or NOS
tubes may be preferred with experi-
mentation.
Tube locations as marked on the
printed circuit board
Install the grounding lug
under the top screw at the rear
of the chassis when reinstalling
the cover.
Owner’s Manual
eleven
Please read the Owner’s Manual completely BEFORE operating the unit.
Power Line Polarity
Set the power line polarity switch to
the “A” position. With the volume
control at its lowest position, place
the line stage input selector in the
position to select the VTPH-2 phono
preamplifier.
Increase the volume to a normal
listening level and check for hum.
Reduce the volume to a lower posi-
tion and play a record. Gradually
increase the volume control to the
desired level and listen closely to the
quality of the reproduction. This will
be used as a baseline for determining
AC polarity.
Place the line stage input selector
to an unused position and change
the AC polarity of the VTPH-2
phono preamplifier by switching the
power line polarity switch to the “B”
position. Repeat the process, listen-
ing to the same recording. Place the
AC polarity switch in the position
that sounds best.
Optimum Performance
With higher definition and detail
available in the musical signal, more
careful attention to the set-up of
other components will yield greater
benefits. We have found that the
best place to start is with the
turntable set-up. Adjustments of
the vertical tracking angle will be
easy to resolve using the Herron
Phono Preamplifier. Users may gain
improved performance by making
fine adjustments. Slight changes in
cartridge tracking force can improve
tracking and position the coils in a
cartridge at the correct position
relative to the magnets.
This can dramatically improve
performance. We recommend that
the VTPH-2 be used with a line
stage having an input impedance of
50,000 Ohms or higher for optimum
performance. Depending on the
cartridge output rating, the line
stage may require an input capacity
of as high as 15 volts rms.
We recommend the use of high
quality interconnecting cables
between the turntable and the
phono stage and between the
phono stage and line stage. It is
very important for achieving best
performance from the VTPH-2 that
the cables between the phono stage
and the line stage be a low capaci-
tance type.
Changing Tubes
When changing tubes, the VTPH-2
should be unplugged and left off for
a minimum of 30 minutes prior to
opening the unit, to insure that haz-
ardous voltages in the power supply
VTPH-2 Herron Audio Vacuum Tube Phono Preamplifier
ten
When changing tubes, the phono stage should be unplugged and left
off for a minimum of 30 minutes prior to opening the unit, to insure that
hazardous voltages in the power supply have time to discharge before
entering the unit.
CAUTION CAUTION CAUTION CAUTION CAUTION CAUTION

VTPH-2 Technical Specifications
VTPH-2 Technical Specifications
Tube complement (Available in two 5 tube factory set configurations)
(4 12AX7, 1 12AT7)
or
(2 12AX7, 3 12AT7)
Gain Moving coil (2 12AX7, 3 12AT7) 64 dB
mode: (4 12AX7, 1 12AT7) 69 dB
Gain Moving magnet (2 12AX7, 3 12AT7) 43 dB
mode: (4 12AX7, 1 12AT7) 48 dB
Frequency response RIAA 20 Hz to 20 kHz 0.1 dB
Signal-to-Noise Ratio: 80 dB, A weighted, inputs shorted
(noise level will be tube dependent)
Output Impedance: 500 ohms nominal (12AT7 “V5” dependent)
Input Impedance:
Moving Coil Inputs: Infinite impedance with no load resistors
connected
NOTE: load resistors can be connected externally via RCA connectors
or soldered in internally
Moving Magnet Inputs: 47,000 (47k) ohms, 100 pF
Absolute Polarity: Non-inverting in both moving coil and
moving magnet modes
Toroidal power transformer
Power requirements: U.S.: 115 VAC 60 Hz, 30 VA
Fuse:
1
⁄
2
amp 250 volt slow blow
Export: 230 VAC 50/60 Hz, 30 VA
Fuse:
1
⁄
4
amp 250 volt slow blow
Overall dimensions: 17.6wide x 4high 10deep
Warranty: 3 years, parts and labor 90 days for tubes
VTPH-2 Herron Audio Vacuum Tube Phono Preamplifier
twelve