Herron Audio VTSP-3A User manual

Owner’s Manual
VTSP-3A
Vacuum Tube
Stereo Preamplifier

VTSP-3A
Table of Contents
General Safety, Installation, 1
and Operation Instructions
Important Safety Instructions 4
Warning 4
Important (UK only) Instructions 5
Introduction 6
Features 8
Design Considerations 10
Front Panel Features 11
Rear Panel Features 13
Remote Control 15
Installation and Operation 16
Changing Tubes 18
Technical Specifications 19
FCC Notice 20
Re-cycling 21
RoHS Compliance 21
©2013 Herron Audio
Division of Herron Engineering, Inc.
12685 Dorsett Road
# 138
Maryland Heights, MO 63043 (St. Louis area)
314.434.5416
www.herronaudio.com

VTSP-3A Owner’s Manual
Please read the Owner’s Manual Completely BEFORE operating the unit
1
General Safety, Installation,
and Operation Instructions
It is important to read this document before attempting to use this product.
Pay close attention to safety instructions.
Appears on the component to indicate the presence of
uninsulated, dangerous voltages inside the enclosure – volt-
ages that may be sufficient to constitute a risk of shock.
Appears on the component to indicate important operation
and maintenance instructions included in the accompany-
ing documentation.
Appears on the component to indicate compliance of with
the EMC (Electromagnetic Compatibility) and LVD (Low-
voltage Directive) standards of the European Community.
WARNING Calls attention to a procedure, practice, condi-
tion, or the like that, if not correctly performed or adhered
to, could result in personal injuries or death.
CAUTION Calls attention to a procedure, practice, condi-
tion, or the like that, if not correctly performed or adhered
to, could result in damage or destruction to part or all of
the component.
Note Calls attention to information that is essential to
highlight.
WARNING
CAUTION
Note

VTSP-3A Owner’s Manual
2
Important Safety Instructions
1. Read these instructions
2. Keep these instructions.
3. Heed all warnings.
4. Follow all instructions.
5. Do not use this apparatus near water.
6. Clean only with a dry cloth. Great care and attention has gone
into the materials chosen to produce the product. A gentle wipe with
a dry, clean cloth is all that is required to remove any dust. Treat it as
you would a fine piece of furniture because that is how they have been
designed.
7. Do not block ventilation openings. Install in accordance with the
manufacturer’s instructions.
8. Do not install near any heat sources such as radiators, heat regis-
ters, stoves, or another apparatus that produces heat.
9. Do not defeat the safety purpose of the polarized or ground-
ing-type plug. A polarized plug has two blades with one wider than
the other. A grounding-type plug has two blades and a third grounding
prong. The wide blade or third prong is provided for safety. If the pro-
vided plug does not fit into the outlet, consult an electrician for replace-
ment of the obsolete outlet.
10. Protect the power cord from being walked on or pinched,
particularly at plugs, convenience receptacles, or the point where it exits
from the apparatus.
11. Only use attachments and accessories specified by the
manufacturer.

VTSP-3A Owner’s Manual
Please read the Owner’s Manual Completely BEFORE operating the unit
3
12. Use only with the cart, stand, tripod, bracket, or table
specified by the manufacturer or sold with the apparatus.
When a cart is used, use caution when moving the cart/
apparatus combination to avoid injury or tip over.
13. Unplug this apparatus during lightning storms or when unused
for long periods of time.
14. Refer all servicing to qualified service personnel. Servicing is re-
quired when the apparatus has been damaged in any way, such as when
the power cord or plug has been damaged; liquid has been spilled or ob-
jects have fallen into the apparatus; or the apparatus has been exposed
to rain or moisture, does not operate normally, or has been dropped.
15. No naked flame sources, such as candles, should be placed on the
apparatus.
16. The appliance coupler is used as the disconnect
device, the disconnect device shall remain readily oper-
able.
17. Terminals marked with this symbol may be considered HAZARDOUS
LIVE and the external wiring connected to these terminals requires in-
stallation by an INSTRUCTED PERSON or the use of ready-made
leads or cords.
18. This exclamation point within an equilateral
triangle is intended to alert the user to the presence of
important maintenance (servicing) instructions in the
literature accompanying the appliance.
Warning! To reduce the risk of fire or electric shock, do not
expose the apparatus to rain or moisture. Do not place objects
containing liquid, such as vases, on this apparatus.

VTSP-3A Owner’s Manual
4
Warning
• TO PREVENT FIRE OR SHOCK HAZARD, DO NOT USE THIS PLUG WITH
AN EXTENSION CORD, RECEPTACLE OR OTHER OUTLET UNLESS THE
BLADES CAN BE FULLY INSERTED TO PREVENT BLADE EXPOSURE
• TO PREVENT FIRE OR SHOCK HAZARD, DO NOT EXPOSE THIS
APPLIANCE TO RAIN OR MOISTURE
• TO PREVENT ELECTRIC SHOCK, MATCH WIDE BLADE PLUG TO WIDE
SLOT AND FULLY INSERT
This lightning flash with an arrow head symbol, within
an equilateral triangle, is intended to alert the user to the
presence of un-insulated “dangerous voltage” within the
product’s enclosure that may be of sufficient magnitude
to constitute a risk of electric shock to the persons.
Warning: To reduce the risk of
electric shock, do not remove
cover (or back), no user-service-
able parts inside. Refer servicing
to qualified service personnel.
This exclamation point within an equilateral triangle is
intended to alert the user to presence of important mainte-
nance (servicing) instructions in the literature accompany-
ing the appliance.

VTSP-3A Owner’s Manual
Please read the Owner’s Manual Completely BEFORE operating the unit
5
IMPORTANT! (U.K. only)
This unit is supplied in the U.K. with mains lead fitted with a moulded 13
amp plug. If, for any reason, it is necessary to remove the plug, please remove
the fuse holder and dispose of the plug safely, out of reach of children.
It must not be plugged into a mains outlet.
The wires in the mains lead supplied with this appliance are coloured in ac-
cordance with the following code:
Green and yellow..............Earth
Blue................................Neutral
Brown.................................Live
WARNING - This appliance MUST be earthed
As the colours of the wires of the mains lead of this appliance may not cor-
respond with the coloured markings identifying the terminals in the plug,
proceed as follows:
The wire which is coloured green-and-yellow must be connected to the
terminal in the plug which is marked with the letter E or coloured green or
green-and-yellow, or by the earth symbol :
The wire which is coloured brown must be connected to the terminal
which is marked with the letter L or coloured red.
The wire which is coloured blue must be connected to the terminal
which is marked with the letter N or coloured black.
If connecting to a BS1363 plug, a 13 amp fuse must be used.
WARNING:
ANY MODIFICATIONS TO THIS PRODUCT NOT EXPRESSLY
APPROVED BY HERRON AUDIO WHO IS THE PARTY RESPON-
SIBLE FOR STANDARDS COMPLIANCE COULD VOID THE USER'S
AUTHORITY TO OPERATE THIS EQUIPMENT.

VTSP-3A Owner’s Manual
6
Thank you for your investment in the Herron Audio VTSP-3A Vacuum Tube
Stereo Preamplifier, a milestone in high-precision audio playback equipment.
The VTSP-3A is a new design, benefiting from insights gained during con-
tinuous refinement of the highly-praised and award-winning VTSP-2. The
care in engineering and manufacturing of this product anticipates a lifetime
of musical enjoyment. Years of research into circuit design and component
performance were applied to the development of the VTSP-3A and new
implementations of components have led to a breakthrough in performance
while maintaining conservative operation for extended tube life. As with all
Herron Audio products, the VTSP-3A is engineered to be reliable and user
friendly.
Manufacturing of the VTSP-3A is performed under the tightest of quality
controls. Its limited production permits hand matching of components to
the most exacting standards in the industry. Tubes are burned in, bench
tested, and matched to extremely tight tolerances, both as sets within a
given unit and to the original design to ensure unprecedented performance
and lack of unit-to-unit variation.
Welcome!

VTSP-3A Owner’s Manual
Please read the Owner’s Manual Completely BEFORE operating the unit
7
The VTSP-3A incorporates an infra-
red remote control for convenient
operation of many of the preampli-
fier’s front-panel functions. This
remote uses 38kHz modulation and
detection of this signal initiates the
VTSP-3A’s decoder circuitry, which
is otherwise dormant in order to
prevent the unwanted noise usu-
ally associated with remote control
circuitry. A flashing red light in the
display window indicates the initia-
tion of the remote control decoding
process in the VTSP-3A. When the
red light is off, this circuitry goes to
“sleep” mode.
The VTSP-3A utilizes two extremely
low distortion precision electronic
stepped attenuators (one for each
channel) in a fashion similar to
the VTSP-1A/166, and VTSP-2. The
VTSP-3A has a total of 100 vol-
ume steps, and the precise volume
level is shown as three digits in the
front-panel display window. The use
of electronic stepped attenuators
ensures continued high-quality per-
formance without any of the oxida-
tion and corrosion that degrades
conventional mechanical stepped
attenuators and volume control
potentiometer wiper contacts.
At startup, the display on the
VTSP-3A goes through a lamp test,
and then successively displays the
model of the unit “SP3A” and the
time in seconds from 60 (while the
filaments and high voltage are slowly
brought on) until the unit automati-
cally un-mutes. The input display will
show the last input in use from the
last time the unit was on. When the
countdown is complete the mute will
be disengaged (if it was not on the
last time the unit was shut down),
the function displays will indicate the
last state of use, and the volume will
be ramped up to a relatively low level
of 10. At this point the user will be
able to change the settings.
The VTSP-3A incorporates circuitry to
switch the phase of the audio signal
by 180 degrees for absolute polarity
control. The amber “Invert” light
on the front panel will indicate if the
phase is being inverted. The phase
switching circuitry of the VTSP-3A is
designed so that no coloration is add-
ed in either mode and the true effects
Features

VTSP-3A Owner’s Manual
8
of recorded phase polarity are audible
in either mode. The invert mode can
be controlled from both the front
panel and the remote control.
Note: When the invert mode of
the VTSP-3A is switched, the unit
automatically mutes before chang-
ing modes in order to prevent any
unwanted “pops” during switching.
The unit unmutes after the invert
mode is changed. The process takes
less than a second.
The display brightness of the VTSP-
3A can be dimmed from both the
remote and the front panel by push-
ing the “Display” button. Operat-
ing the “Display” button again will
return the brightness to its previous
setting. The blue “Display” indicator
on the front panel indicates dim-
display mode.
Source input selection in the VTSP-
3A incorporates gold-contact sealed
relays located at the input connec-
tors, keeping the signal path length
to an absolute minimum. This
innovative configuration eliminates
the distortion-generating wipers
of conventional selectors and long
runs of wire from the rear panel to
the switch. An additional benefit of
using sealed relays, the contacts are
not prone to corrosion, dirt, or the
same kind of wear as conventional
selector switches.
The VTSP-3A has a power-polarity
switch on the back panel for revers-
ing the power line polarity connec-
tion to the primary of the power
transformer. This can be used to
minimize the capacitive reactance
effects from the power line on the
audio quality of the unit and system.
This switch should be operated with
the unit muted and comparison after
unmuting can be made in order to
determine the best-sounding power
polarity switch setting.
The “Video” input of the VTSP-3A
can be placed in unity-gain mode
by pressing and holding the “Video”
button on the front panel for a few
seconds. The volume display will
indicate “PAS” on the display when
the pass-through mode is initiated;
only the video input will be at unity
gain. Selecting any other input will
shut off the pass-through mode, and
the volume will return to 10.
Note: The pass-through mode
cannot be selected from the
remote control.

VTSP-3A Owner’s Manual
Please read the Owner’s Manual Completely BEFORE operating the unit
9
The VTSP-3A has an instant shut-
down circuit that mutes the output
upon loss of full line voltage (power
loss). This feature provides protec-
tion from loud “pops” or noises from
input equipment that may damage
speakers. With a power loss of more
than a few seconds, the unit will to-
tally shut down, and go through the
full start-up sequence when power is
restored. If the power outage is brief,
the unit will mute and wait 10 to 15
seconds to unmute when the power
is restored. This delay will allow
DC signals from input components
enough time to normalize so that
loud “pops” will be minimized.

VTSP-3A Owner’s Manual
10
• Multifunction remote control
• Volume level display (0 - 100)
• Unity gain pass-through function-initiated by holding video button
• Two gain modes—selected by holding the phono button on the front
panel
• Class A operation
• Switchable absolute polarity
• 100-step electronic volume control system with precision tracking
and very low distortion
• Full-range, infinite-resolution indirect signal path balance control
• Stereo/mono switch
• Mute control
• Display brightness control
• Tape out/in loop
• Low noise design
• High input-signal capacity without overload
• Automatic muting at startup and shutdown
• Gold plated, Teflon-insulated RCA connectors
• Handpicked components for accurate response and consistent
unit-to-unit quality
• Reversing power line (AC) polarity switch for minimizing line-to-chassis
reactive currents and noise pickup
• Each unit is given an extensive burn-in, including rigorous bench
and listening tests
Design Considerations

VTSP-3A Owner’s Manual
Please read the Owner’s Manual Completely BEFORE operating the unit
11
The three-digit volume level display
in the display window at the center
of the front panel indicates the vol-
ume level (0 to 100) and the parame-
ters of the unit during start-up. It also
indicates “PAS” during pass-through
mode and Ldb or Hdb gain modes
when the phono button is pushed.
The selected input is indicated by
the blue lights on the left side of
the front panel.
These inputs are:
• Phono
• Aux
• CD
• Tuner
• Video
The VTSP-3A has two gain modes for
system matching. The VTSP-3A gain
modes can be switched by holding
the phono button in for 2 seconds.
The high gain “Hdb” mode has 14
db gain and the low gain “Ldb”
mode has 8 db total gain. The “Ldb”
gain mode is indicated by a decimal
point in the volume level display
window. The mode “Hdb” or “Ldb”
are also indicated in the volume
level display window anytime the
phono mode button is pressed on
the front panel or from the remote
control. The Ldb mode is indicated
by a decimal point in the volume
display. The gain can only be
changed from the front panel
phono button and not from the
remote control.
The tape input (loop) indicator is
on the right side of the front panel.
This input can be selected from
either the front panel or the remote
control after the unit has gone
through the start-up sequence.
The balance control provides a
full range of adjustment for rela-
tive balance between the right and
left channels. In the centered posi-
tion, each channel is equal in signal
sensitivity. Rotating the balance
Front Panel Features

VTSP-3A Owner’s Manual
12
control in the clockwise direction (to
the right) decreases the volume in
the left channel relative to the right
channel. Rotating the balance control
in a counter-clockwise direction (to
the left) decreases the volume in the
right channel relative to the left.
In the fully clockwise or counter-
clockwise position, the left or right
channel respectively will be muted.
Normal operation is provided when
the balance control is in the centered
position. The “Balance” knob operates
an infinitely variable control that is
barely in the circuit at center position.
Note: The balance control cannot
be operated from the remote.
The “Volume” knob operates
a stepped encoder. Rotating the
volume knob to the right increases
the volume level, or to the left to
decrease the volume level. The level
is displayed from 0 to 100 in the dis-
play window. The volume can also be
controlled from the remote control.
Note: Since the volume control is
a stepped attenuator the individual
steps of the volume control as it
is raised or lowered may produce
“clicks” for a short period after the
unit, or input device has been turned
on. This will be most noticeable be-
tween steps 29 and 30. These “clicks”
are the result of a D.C. voltage at the
input of the unit causing instanta-
neous D.C. level shifts as the volume
control steps up or down. This condi-
tion will usually subside after a few
minutes as the D.C. level at the input
from the source component dissipates.
The red “Mute” light indicates
that the preamplifier is in mute mode
and no signal will pass through the
unit. During mute, the stepped at-
tenuators are set to zero level and the
output is shorted by a relay. The mute
mode can be initiated or disengaged
from the front panel or the remote
control.
The orange “Mono” light indi-
cates that the preamplifier is in mon-
aural mode. In mono mode, the unit
mixes the left and right signals to
monaural so that the signals coming
from the left and right channels are
the same. Mono mode can be initi-
ated or disengaged from the front
panel or the remote control.
The amber “Invert” light in-
dicates that the preamplifier is in
phase-inverting mode. The invert
mode reverses the absolute phase of
both channels. The invert mode can
be initiated or disengaged from the
front panel or the remote control.

VTSP-3A Owner’s Manual
Please read the Owner’s Manual Completely BEFORE operating the unit
13
The amber “Tape” light indicates
that the tape input has been select-
ed. The tape input allows the user
to loop the selected input (source)
signal out from the tape output
through a tape machine or other
processor, and listen to the signal
coming back into the tape input.
The tape input mode can be initiated
or disengaged from the front panel
or the remote control.
The blue “Display” light indicates
display mode. The display mode can
be initiated or disengaged from the
front panel or the remote control. Al-
ternate function of the display mode
dims the front panel display.
The rear panel was designed for
flexibility and ease of access to less-
frequently used functions. The high-
precision RCA input jacks are gold-
plated to minimize signal-degrading
corrosion. The special Teflon insula-
tion material in the RCA connectors
maintains purity of the signal from
the input cable into the unit.
Power Connection
An IEC power cord connector is
provided for attaching either the
factory-provided power cord or
another (appropriate cord) chosen
by the user.
Power Switch
When the unit’s POWER switch is
placed in the on (“up”) position, the
unit is powered up. At power up, the
unit is automatically muted until full
operational capabilities are reached
and the voltages are stable at the
tubes. When the switch is moved to
the off position, the unit is automat-
ically muted and powered down.
Power Line
Polarity Switch
This switch selects the power-line
polarity. AC line polarity may affect
performance. The following is the
Rear Panel Features

VTSP-3A Owner’s Manual
14
recommended procedure for deter-
mining the best operation:
• With the mute engaged, set the
power line polarity switch to the
“A” position then disengage the
mute.
• Set 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.
• Engage the mute function and
change the AC polarity of the pre-
amplifier by switching the power
line polarity switch to the “B”
position then disengage the mute
for listening. Repeat the process,
listening to the same source.
• Place the AC polarity switch in
the position that sounds best. It
may be necessary to change the
AC polarity if you make other
equipment or power connection
changes in your audio system.
Note: The AC polarity switch
should only be operated with
the unit muted.
Inputs
The inputs are grouped by channel:
the upper bank contains the left-
channel inputs, the lower contains
the right-channel inputs. The left/
right input pairs are arranged verti-
cally. The input pairs are arranged
on the back in the same order as
on the front panel and remote
(with the exception of the tape loop
input).
RCA input plugs should be inserted
firmly into the input jacks while
the unit is powered down. Any
individual ground-bleed connections
should be connected to the gold
ground lug located near the end of
the banks of input jacks.
Outputs
There are two types of outputs in
the VTSP-3A. The main outputs are
intended for connection to high-
quality power amplifiers or a multi-
channel electronic crossover. Two
pairs of main outputs are provided
so that users may distribute the au-
dio signal to multiple amplifiers.
The tape outputs are provided to
allow monitoring of the selected
audio signal after the input relays.
The signal from the tape output
corresponds to the input chosen by
the user and displayed on the front
panel.

VTSP-3A Owner’s Manual
Please read the Owner’s Manual Completely BEFORE operating the unit
15
Remote control functions:
• Input Selection
• Absolute Polarity
• Display Brightness
• Volume, Mute, and Mono/Stereo
The remote control is laid out in a
fashion similar to the front panel of
the VTSP-3A.
The input controls on the left side
(top to bottom) are in the following
order:
• Phono
• Aux
• CD
• Tuner
• Video
The volume is controlled with the
two white buttons at the top center of
the remote. The V2 button on the left
decreases the volume. The V1 button
on the right increases the volume.
The controls on the right side of the
remote (top to bottom) are in the
same order as the front panel:
• Mute
• Mono
• Invert
• Tape
• Display
NOTE: The balance control cannot
be operated from the remote control.
The remote control will only con-
trol the unit if the top of the remote
is pointed toward the display
window of the VTSP-3A. The remote
control uses two CR2025 3-volt
lithium batteries.
Note: the + indicator on the
batteries must be facing
the back side of the remote.
Installing the batteries in the
wrong direction may damage
the remote control.
Remote Control
Remote Control

VTSP-3A Owner’s Manual
16
Operation of the Herron VTSP-3A
stereo preamplifier is straightfor-
ward. As with any fine audio compo-
nent, careful setup and integration
into one’s system is important for
optimum performance, safety, and
reliability. Please read through the
following setup instructions com-
pletely prior to operating the unit.
Procedure
1. Position the unit in a well-venti-
lated area on a firm, stable surface,
away from equipment that gener-
ates alternating magnetic fields
such as motors, transformers, etc.
Magnetic fields of this type can in-
troduce hum into the signal path.
Good ventilation is impor-
tant in order to prevent
overheating of the unit.
Excess heat will shorten the
life of the unit.
2. Connect the signal cables from
the source components (CD,
phono preamplifier, VCR, tuner,
etc.) to the VTSP-3A’s rear panel
jacks, left-to-left and right-to-
right. Connect any ground bleed
wires to the ground connector
of the phono preamplifier.
3. Plug the amplifier and tape
recorder input cables into the
corresponding outputs, left-to-
left and right-to-right.
4. Plug the power cord into the
IEC socket. Make sure it is firmly
seated prior to inserting the
plug into an AC outlet.
5. Plug the power cord into a
115-volt (U.S. spec units) AC
outlet.
6. Power up the source
components.
7. Power up the VTSP-3A by
switching on the power switch.
8. Once the VTSP-3A is powered
up and operating, power up the
downstream amplifier(s) and
crossover, if any, as recommend-
ed by their manufacturers.
9. With the Volume control in the
lowest position, gradually in-
crease the gain until the desired
level is reached.
10. When the listening session is
complete, it is suggested, but not
required, that the VTSP-3A be
powered down after the crossover,
amplifiers, and tape recorder, and
before the source components.
Installation and Operation

VTSP-3A Owner’s Manual
Please read the Owner’s Manual Completely BEFORE operating the unit
17
Power Requirements
It is recommended that the VTSP-3A
stereo preamplifier be connected to
the same power source (dedicated
circuit) as the other source compo-
nents (phono stage, turntable, CD
player, SACD player, etc.) and power
amplifiers in the audio system.
This will reduce the component-to-
component differential RFI (radio
frequency interference from power
lines which act as receiving anten-
nas) level that will be required to be
conducted by the audio intercon-
nects, which are a very important
part of the audio chain. RFI can add
brightness and lack of clarity to an
audio system.
With the higher definition and
detail available through the
VTSP-3A, careful attention to the
setup of other components will
yield significant benefits. There may
also be considerable gains from the
upgrade of existing electronics.
We recommend the use of high-
quality interconnecting cables be-
tween the source components and
the VTSP-3A, and between the
VTSP-3A and components down-
stream of it (the power amplifiers
and speakers).
Due to the increased definition of
detail, it may be necessary to make
minor adjustments in speaker posi-
tion or active crossover settings to
optimize their performance. We
have determined that minor time
alignment changes in a setup can
produce major advances in the over-
all quality of the reproduced signal,
bringing the listener closer to the
original performance.

VTSP-3A Owner’s Manual
18
When changing tubes, the VTSP-3A 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.
We do not recommend changing
tube brands for the purposes of
“improving sonic performance.”
Tubes of even the same part number
(6922 in the case of the VTSP-3A)
from different manufacturers and
different production lots generally
vary considerably in many operating
parameters. The Herron VTSP-3A
stereo preamplifier has been op-
timized for the tubes that were
supplied by the factory. The original
tubes should provide many years
of good performance due to the
design’s conservative plate voltage
and current operating requirements.
If replacement tubes are required,
Herron Audio recommends the use
of our factory-matched sets of tubes.
These tubes have been selected for
their superior performance.
All 6 tubes in the Herron VTSP-3A
are of the type 6922.
When changing tubes, the VTSP-3A
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
have time to discharge.
Left channel:
Tubes V1, V2, and V3
Right channel:
Tubes V4, V5, and V6
Changing Tubes
Tube Locations
Front panel
Back of unit
CAUTION