Herron Audio VTPH-1 User manual

Owner’s Manual
Please read the Owner’s Manual completely BEFORE operating the unit.
VTPH-1
Vacuum Tube
Phono Preamplifier
Vacuum Tube
Phono Preamplifier
Owner’s Manual
VTPH-1

Owner’s Manual
Please read the Owner’s Manual completely BEFORE operating the unit.
Thank you for your investment in
the Herron Audio Vacuum Tube
Phono Preamplifier, a masterpiece
of high-precision analog audio play-
back equipment. It is designed to be
the finest product of its type avail-
able. The care in engineering and
manufacturing of this product
anticipates a lifetime of musical
enjoyment.
The Herron Phono Preamplifier
was created to address the retrieval
of musical information from vinyl
LPs without any compromise. The
original design was 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 to meet
the requirements for a more durable
unit manufactured in larger quanti-
ties. In the process, important
refinements were developed and dis-
coveries were made about tolerances
and the threshold of human hearing
limits.
This product is engineered to be
user friendly, and overcomes the
fears that many have expressed
concerning the use of vacuum tubes
in their systems. Its limited produc-
tion ensures that the components in
each unit are matched to the highest
standards in the industry. Manufac-
turing of the unit is performed under
the tightest of quality controls.
Components are hand-matched to
exacting standards—to ensure iden-
tical unit-to-unit performance. For
example, capacitors in the RIAA
equalization stage are hand matched
to tolerances of better than 0.1%.
Tubes are burned in, bench tested,
and hand-matched both across units
and to the original design. These
techniques ensure
that each unit performs to the high
standards established in the develop-
ment of the original prototypes. This
costly process is reflected in the
unprecedented 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 Phono Preamplifier to
provide the highest musical satisfac-
tion without the artifacts produced
by most other tube-based compo-
nents. This power supply provides a
one
Welcome!
Welcome!
Herron Audio Vacuum Tube Phono Preamplifier
Table of Contents
1Introduction
3Models
3Design Considerations
4Front Panel Information
5Rear Panel Information
6Installation and Operation
7Cartridge Loading
8Power Line Polarity
8Optimum Performance
9Changing Tubes
10 Technical Specifications
© 2002 Herron Audio
Division of Herron Engineering, Inc.
12685 Dorsett Road
# 138
St. Louis, MO 63043
314.434.5416
314.434.6629 fax
Owner’s ManualHerron Audio Vacuum Tube Phono Preamplifier

Owner’s Manual
Please read the Owner’s Manual completely BEFORE operating the unit.
three
VTPH-1MM moving magnet version (use with cartridges above
1 millivolt output)
VTPH-1MC PLUS moving coil version (same as the MM version with an
additional FET front end amplifier)
Design Considerations
• All-tube signal path (moving magnet version)
• Passive RIAA equalization for accurate phase and amplitude response
• Star grounding for low interference susceptibility and clean signal path
• Zero feedback—no feedback loops in the audio circuitry
• Low noise
• No switches in the signal path
• High input signal capacity without overload; see technical specifications
• Gold plated TIFF RCA and ground connectors
• Audio path capacitors are polypropylene and polystyrene
• Hand-picked components for accurate response
• Automatic muting at startup and shutdown
• 78,000 µF 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
• Rugged—0.10" thick aluminum chassis with 0.25" thick faceplate
• 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, filament voltage, and output (mute release)
• Each unit is given a 48-hour burn-in, including rigorous bench and
listening tests
VTPH-1 Models
VTPH-1 Models
Herron Audio Vacuum Tube Phono Preamplifier
rigid voltage source to the tubes,
producing remarkable resolution of
musical events in time and sound
stage.
The circuit board layout was
engineered with all of its electrical
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
Phono Preamplifier, along with its
conservative design and operating
parameters, means that owners can
expect the industry’s highest level of
performance to be maintained over
the extended life of the unit.
Operating the Herron Phono
Preamplifier is easy and straight-
forward. The unit has been designed
to be exquisitely simple and user
friendly, with its operational readi-
ness 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 functioning correctly.
Last and most importantly, careful
listening tests are made in compari-
son to a reference 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
performance 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.
two

Owner’s Manual
Please read the Owner’s Manual completely BEFORE operating the unit.
five
Rear Panel Features
Power Switch On / Off switch (1 = On, 0 = Off)
AC Polarity Allows the user to select the AC polarity 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 Used to connect the phono ground bleed wire to the unit.
Connects to the star ground system in the unit.
Input Jacks Used to connect the input signal from the cartridge to the
unit. The left channel is closest to the top of the unit.
Output Jacks Used to connect the unit to a line stage or preamp.
Optimum performance is gained by using the Herron
Audio Line Stage, though good performance can also
be derived by using other top-quality preamps. The left
channel is closest to the top of the unit.
Model Number VTPH-1MM for moving magnet (Tube only, 44 dB gain
nominal)
VTPH-1MC PLUS for moving coil (22 dB gain FET front
end
+ 44 dB tube section)
Switch
(Power Line)
Connector
The Rear Panel
The Rear Panel
Herron Audio Vacuum Tube Phono Preamplifier
four
Front Panel Indicators
The VTPH-1 features a fully-functional front panel capable of monitoring the
operational readiness of the preamp. When the VTPH-1 is powered up, the
automute feature is engaged until the unit is ready for operation. The first indi-
cator on the panel is the POWER LED, which indicates the unit has been turned
on. After a few moments, the FILAMENTS LED gradually brightens, as the volt-
age to the filaments slowly increases. When the unit is ready to operate, the
OUTPUTS LED comes on 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
long period of time.
The Front Panel
The Front Panel
Owner’s ManualHerron Audio Vacuum Tube Phono Preamplifier

Please read the Owner’s Manual completely BEFORE operating the unit.
!!!!
When changing cartridge loading resistors, 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.
Loading resistors should only be changed by technically qualified personnel.
Care needs to be taken during this procedure in order to prevent damage
by static electricity to the field effect transistors in the moving coil input
stage. A grounding wrist strap is highly recommended.
Keep the cartridge load resistor leads short, as shown, to prevent hum pick-
up. Install the grounding lug under the top screw at the rear of the chassis
when reinstalling the cover.
The Herron Phono Preamplifier
is available in different configu-
rations to suit the type of phono
cartridge being used. User adjust-
ments are minimized to simplify
operations. For moving magnet
units, the input impedance is set
at 47,000 ohms in parallel with
100 pF (grid to plate capacitance
of the first 12AX7 multiplied by
the gain—the "Miller Effect").
For moving coil units, optional
internal cartridge loading
resistors can be soldered to the
input connectors, as shown, in parallel with existing 47,000 ohm resistors on
the FET amplifier board. Loading resistor switch contacts would compromise
performance at the small signal levels that are generated by a moving coil car-
tridge. The cartridge loading resistors may be changed by the user, dealer, or
factory, with values appropriate to specific cartridge requirements.
CAUTION CAUTION CAUTION CAUTION CAUTION CAUTION
seven
Optional cartridge loading resistors shown at input
connector terminations of the FET amplifier board.
Cartridge Loading
Cartridge Loading
LOADING
RESISTORS
1. Position the unit in a well-venti-
lated area on a firm, stable
surface, away from equipment
that generates alternating mag-
netic fields such as motors,
transformers, etc. Magnetic fields
of this type can introduce hum
into the signal path.
2. Connect the phono leads to the
phono preamp left-to-left and
right-to-right. Connect the
phono ground bleed wire to the
ground connector of the phono
preamp.
3. Plug the line stage leads into the
output, left-to-left and right-to-
right.
4. Plug the power cord into the
phono preamp. Make sure it is
firmly seated into the IEC socket
prior to inserting the plug into
an AC outlet.
5. Plug the power cord into a 120
volt (U.S. spec units) AC outlet.
6. Power up the unit by switching
on the power switch.
7. Observe the LEDs for the appro-
priate operation (see the Front
Panel Indicators section). Listen
carefully for the click of the auto-
mute engaging the outputs.
8. Once the unit is powered up and
operating, place the line stage
input selector switch to a posi-
tion selecting an unused or
deactivated input.
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 preamp. With the vol-
ume control of the line stage set
at its lowest position, select the
phono preamp. Gradually
increase the volume control until
a normal listening level is
reached.
six
The operation of the Herron 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.
Procedure:
Installation and Operation
Installation and Operation
Owner’s ManualHerron Audio Vacuum Tube Phono Preamplifier

Please read the Owner’s Manual completely BEFORE operating the unit.
!!!!!
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.
Please read the Owner’s Manual completely BEFORE operating the unit.
Changing Tubes
We do not recommend changing
tubes for the purposes of “improving
sonic performance.” Tubes of even
the same part number (12AX7 for
instance) from different manufactur-
ers and different production lots
generally vary considerably in many
operating parameters. The Herron
Phono Preamplifier has been
optimized for the tubes that were
supplied by the factory. If tube
replacement is required, channel-to-
channel gain matching can be done
using the left and right bias controls
on the printed circuit board. Do not
try to compensate for large gain
differences (more than 0.5 dB) as
this will degrade performance. 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 Preamp-
lifier.
nine
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.
CAUTION CAUTION CAUTION CAUTION CAUTION CAUTION
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 phono preamp. Increase
the volume to a normal listening
level and check for hum.
Reduce the volume to a lower
position 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 phono preamp
by switching the power line polarity
switch to the "B" position. Repeat the
process, listening to the same record-
ing. Place the AC polarity switch in
the position that sounds best.
eight
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 bene-
fits. We have found that the best place
to start is with the turntable set-up.
Adjustments of the vertical tracking
angle will be easier 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 posi-
tion relative to the magnets. This can
dramatically improve performance.
We recommend that the VTPH-1
be used with a line stage having an
input impedance of no less than
50,000 Ohms. Impedances below this
may degrade the performance of the
unit. 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-1 that the cables between the
phono stage and the line stage be a
low capacitance type.
Along with careful determination
of optimum AC polarity, compensa-
tion for absolute signal polarity
should be considered. The VTPH-
1MM is noninverting, the VTPH-1MC
is inverting in absolute phase.
Owner’s ManualHerron Audio Vacuum Tube Phono Preamplifier

Herron Audio Vacuum Tube Phono Preamplifier
VTPH-1 Technical Specifications
VTPH-1 Technical Specifications
Tube complement: 4 x 12AX7WA/B, 1 x 12AT7WC
Frequency Response: RIAA 1 Hz to beyond 100 kHz,
20 Hz to 20 kHz +/- 0.1dB
Gain: VTPH-1MM 44dB nominal at 1 kHz,
channels matched to within 0.05 dB
VTPH-1MC PLUS 66 dB nominal at 1 kHz,
channels matched to within 0.05 dB
Signal-to-Noise Ratio: VTPH-1MC 80 dB, A weighted, inputs shorted,
AC polarity set
Output Impedance: 500 ohms nominal (recommended load 50 k ohms
or higher)
Input Impedance: VTPH-1MM 47,000 ohms, 100 pF
VTPH-1MC PLUS 47,000 ohms, 100 pF plus optional
internal load resistors at input terminals
Absolute Polarity: VTPH-1MM noninverting
VTPH-1MC PLUS noninverting
Power Supply: 78,000 µF of energy storage
4 levels of high voltage regulation
Regulated soft start DC filament supply
Regulated tube bias supply
Toroidal power transformer
Power requirements: U.S.: 120 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
Input capacity: VTPH-1MM up to 300 mv at 1 kHz,
1 volt at 10 kHz (output unloaded)
VTPH-1MC PLUS up to 30 mv at 1 kHz,
100 mv at 10 kHz (output unloaded)
Overall dimensions: 19" wide x 3.5" high x 10" deep
Warranty: 5 years, parts and labor
90 days on tubes
Manufactured by Herron Audio Division of Herron Engineering
St. Louis, Missouri
Herron Audio Vacuum Tube Phono Preamplifier