Herron Audio VTSP-3A Manuel utilisateur

VTSP-3A

Vacuum Tube

Stereo Preampliﬁer

Owner’s Manual

Vacuum Tube

Stereo Preampliﬁer

Welcome!

Thank you for your investment in the Herron Audio VTSP-3A Vacuum

Tube Stereo Preampliﬁer, a milestone in high-precision audio playback equip-

ment. The VTSP-3A is a new design, beneﬁting from insights gained during

continuous 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 imple-

mentations 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.

Owner’s Manual

VTSP-3A Vacuum Tube Stereo Preampliﬁer

Please read the Owner’s Manual completely BEFORE operating the unit.

one

VTSP-3A Vacuum Tube Stereo Preampliﬁer

Division of Herron Engineering, Inc.

12685 Dorsett Road

# 138

Maryland Heights, MO 63043 (St. Louis area)

314.434.5416

www.herronaudio.com

Table of Contents

Introduction 1

Features 2

Design Considerations 5

Front Panel Features 6

Rear Panel Features 8

Remote Control 10

Installation and Operation 11

Changing Tubes 13

Technical Speciﬁcations 14

The VTSP-3A incorporates an

infrared remote control for conve-

nient operation of many of the

preampliﬁer’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 pre-

vent the unwanted noise usually

associated with remote control cir-

cuitry. 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 simi-

lar 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

performance without any of the oxi-

dation and corrosion that degrades

conventional mechanical stepped

VTSP-3A Vacuum Tube Stereo Preampliﬁer

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 sec-

onds from 60 (while the ﬁlaments and

high voltage are slowly brought on)

until the unit automatically un-mutes.

The input display will show the last

input in use from the last time the unit

was on. When the countdown is com-

plete 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 rela-

tively 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 sig-

nal 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

added in either mode and the true

effects of recorded phase polarity are

audible in either mode. The invert

two

Features

Owner’s Manual

Please read the Owner’s Manual completely BEFORE operating the unit.

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 automat-

ically mutes before changing 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

pushing the “Display” button. Oper-

ating 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 con-

nectors, 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 reversing the power line polarity

connection 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 indi-

cate “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 vol-

ume will return to 10.

Note: The pass-through mode

cannot be selected from the remote

control.

three

The VTSP-3A has an instant shut-

down circuit that mutes the output

upon loss of full line voltage (power

loss). This feature provides protection

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 totally shut

down, and go through the full start-

VTSP-3A Vacuum Tube Stereo Preampliﬁer

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.

four ﬁve

Owner’s Manual

Please read the Owner’s Manual completely BEFORE operating the unit.

• 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

• Class A operation

• Switchable absolute polarity

• 100-step electronic volume control system with precision tracking

and 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

The three-digit volume level display

in the display window at the center of

the front panel indicates the volume

level (0 to 100) and the parameters of

the unit during start-up. It also indi-

cates “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”

VTSP-3A Vacuum Tube Stereo Preampliﬁer

mode has 8 db total gain. The “Ldb”

gain mode is indicated by a decimal

point in the volume level display win-

dow. The mode “Hdb” or “Ldb” are

also indicated in the volume level dis-

play window anytime the phono

mode button is pressed on the front

panel or from the remote control.

The Ldb mode is indicated by a deci-

mal 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 relative bal-

ance between the right and left

channels. In the centered position,

six

Front Panel Features

Owner’s Manual

Please read the Owner’s Manual completely BEFORE operating the unit.

each channel is equal in signal sensi-

tivity. Rotating the balance control in

the clockwise direction (to the right)

decreases the volume in the left chan-

nel 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 bal-

ance 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 vol-

ume 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

between steps 29 and 30. These

“clicks” are the result of a D.C. volt-

age at the input of the unit causing

instantaneous D.C. level shifts as the

volume control steps up or down.

This condition will usually subside

after a few minutes as the D.C. level

at the input from the source compo-

nent 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 atten-

uators 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

monaural 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 initiated

or disengaged from the front panel or

the remote control.

The amber “Invert” light indi-

cates 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.

seven

The amber “Tape” light indicates

that the tape input has been selected.

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

VTSP-3A Vacuum Tube Stereo Preampliﬁer

be initiated or disengaged from the

front panel or the remote control.

The blue “Display” light indicates

that the front panel displays are in

dim mode. The display mode can be

initiated or disengaged from the front

panel or the remote control.

eight

Rear Panel Features

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

insulation material in the RCA connec-

tors maintains purity of the signal

from the input cable into the unit.

Power Connection

An IEC power cord connector is pro-

vided for attaching either the

factory-provided power cord or

another 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 automati-

cally muted and powered down.

Owner’s Manual

Please read the Owner’s Manual completely BEFORE operating the unit.

Power Line Polarity Switch

This switch selects the power-line

polarity. AC line polarity may affect

performance. The following is the rec-

ommended procedure for determining

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

preampliﬁer 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 audio

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 corre-

sponds to the input chosen by the

user and displayed on the front panel.

nine

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 V!button on the left

decreases the volume. The V"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

VTSP-3A Vacuum Tube Stereo Preampliﬁer

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.

ten

NOTE: the "indicator on

the batteries must be fac-

ing the back side of

the remote. Installing the

batteries in the wrong

direction may damage

the remote control.

The remote Control

The Remote Control

Owner’s Manual

Please read the Owner’s Manual completely BEFORE operating the unit.

Operation of the Herron VTSP-3A

stereo preampliﬁer is straightforward.

As with any ﬁne audio component,

careful setup and integration into

one’s system is important for opti-

mum performance, safety, and

reliability. Please read through the fol-

lowing setup instructions completely

prior to operating the unit.

Procedure

1. Position the unit in a well-

ventilated 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.

Good ventilation is important

in order to prevent overheat-

ing 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 compo-

nents.

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

recommended by their

manufacturers.

9. With the Volume control in the

lowest position, gradually

increase 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.

eleven

Installation and Operation

Power Requirements

It is recommended that the VTSP-3A

stereo preampliﬁer be connected to

the same power source (dedicated cir-

cuit) as the other source components

(phono stage, turntable, CD player,

SACD player, etc.) and power ampli-

ﬁers in the audio system. This will

reduce the component-to-component

differential RFI (radio frequency inter-

ference) 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 ben-

eﬁts. There may also be considerable

VTSP-3A Vacuum Tube Stereo Preampliﬁer

gains from the upgrade of existing

electronics.

We recommend the use of high-

quality interconnecting cables

between 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.

twelve

!!!!!

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 before

entering the unit.

CAUTION CAUTION CAUTION CAUTION CAUTION CAUTION

Changing Tubes

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.

Owner’s Manual

Please read the Owner’s Manual completely BEFORE operating the unit.

We do not recommend changing

tube brands for the purposes of

“improving sonic performance.”

Tubes of even the same part num-

ber (6922 in the case of the

VTSP-3A) from different manufac-

turers and different production lots

generally vary considerably in

many operating parameters. The

Herron VTSP-3A stereo preampliﬁer

has been optimized 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 recom-

mends the use of our

factory-matched sets of tubes.

These tubes have been selected

for their superior performance.

thirteen

fourteen

Frequency response: 1 Hz to beyond 100 kHz,

20 Hz to 20 kHz "/!0.1 dB volume at 30

Output impedance: 100 ohms nominal at 1 kHz

Input impedance: 100,000 Ohms

Gain: 14 dB in Hdb mode, 8 dB in Ldb mode

Volume control: 100-position electronic stepped attenuator,

maximum differential 0.1 dB channel

to channel

Absolute polarity: Switchable

Front panel: Available in black or clear anodized aluminum

Tubes: Qty. 6, 6922 dual triodes

Dimensions: 17.6” wide #4” high #10.5” deep

Warranty: 3 years, parts and labor; tube warranty: 90 days

VTSP-3A Vacuum Tube Stereo Preampliﬁer

Technical Speciﬁcations

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