Balanced Audio Technology VK-31 User manual

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VK-31
WARRANTY REGISTRATION FORM
Unit Serial Number: _______________________________________
Customer Name: _______________________________________
Address: _______________________________________
_______________________________________
Date of Purchase: _______________________________________
Purchased From:
Dealer Name: _______________________________________
Address: _______________________________________
_______________________________________
IMPORTANT NOTE:
In order to receive the full five year product warranty, please mail this
completed form together with a copy of your sales receipt to Balanced Audio
Technology at the address below, within thirty days of purchase.
Failure to do so will result in the product being warrantied for one year
from the date of manufacture.
1300 First State Blvd. Suite A Wilmington, DE 19804
Tel: [phone] Fax: [phone]

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VK-31
Vacuum Tube
Balanced Stereo Preamplifier
Owner's Manual
1300 First State Blvd. Suite A Wilmington, DE 19804
Tel: [phone] Fax: [phone]

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TABLE OF CONTENT
INTRODUCTION 4
Package Content 4
Physical Placement 5
Connecting to your system 5
FRONT PANEL CONTROLS 6
VK-31 Power On sequence 6
Turning the VK-31 Off 6
PHASE Button and LED 7
MONO button and LED 7
MUTE button and LED 7
INPUT selection 7
VOLUME knob 7
DISPLAY format 8
FUCTION button 8
DISPLAY ON-OFF function 9
MUTE function 9
VK-31 PROGRAMMABLE FUNCTIONS 10
Parameter Definitions 11
PROGRAMMING THE VK-31 11
BALANCE adjustment 11
VOLUME offsets 12
PHASE 13
MONO/STEREO 13
MAXIMUM gain 13
FIXED gain 14
DISPLAY MODE 14
INPUT NAME 15
REMOTE CONTROL FUNCTIONS 16
Volume Up/Down 16
Mute 16
Fade 16
Input 17
Display/Power 17
Fuse Protection 17
Servicing 17
Cleaning 17
Warranty 18

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INTRODUCTION
Thank you for your purchase of the Balanced Audio Technology VK-31 preamplifier.
Please read this owner's manual to obtain the full benefit of the VK-31 in your system. It will
provide you with the needed safety information and operating procedures for this exceptional
unit.
WARNINGS:
To prevent the possibility of serious injury, electrical shock or fire:
DO NOT operate with the cover removed.
DO NOT expose to rain or moisture.
DO NOT defeat the ground power-plug.
DO NOT replace fuse with anything other than the same type and rating as supplied by the factory.
Package Contents
Included in the box should be the following:
Description Quantity
VK-31 Preamplifier 1
Power Cord 1
Spare Fuse 1
Torx Wrench (T-10) 1
Spare Top Cover Screws 5
User’s Manual 1
VK-R3 Remote Control (If ordered)
Save all the packaging material in a safe dry area for the unlikely event that you need to
return the VK-31 to the factory for service.

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PHYSICAL PLACEMENT
It is recommended that you provide at least 6" of free space around the unit for proper ventilation.
Mount the unit on a hard surface with proper ventilation underneath.
Do not stack the VK-31 preamplifier on top of other units, nor vice versa.
CONNECTING THE VK-31 TO YOUR SYSTEM
Balanced Components
Use balanced XLR interconnects. All input and output connectors are clearly marked on the back
panel.
Note: The VK-31 XLR connectors are wired as follows:
Pin 1: common/shield
Pin 2: positive
Pin 3: negative
For the VK-31, use the Main 1 XLR Output for connection to your balanced power amplifier. The
Output 2 is configured as an RCA connector output.
Single-Ended Components
Single-ended components have RCA connectors. The VK-31 preamplifier is designed to
work with mix of single-ended and balanced components connected to its inputs and outputs. If
more single ended components need to be connected to the preamplifer, then the XLR inputs or
outputs can be used for that in conjunction with RCA/XLR adapters. These adapters are available
from an authorized Balanced Audio Technology dealer at a nominal charge.
Two types of adapters are available:
Input Adapters: RCA Female to XLR Male
Output Adapters: RCA Female to XLR Female.

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VK-31 FRONT PANEL CONTROLS
STANDBY Button and LED
The Standby button is used to turn the unit ON and OFF and to switch the preamplifier into its
Standby mode. The LED indicates the status of the unit’s power circuitry and has four state:
LED OFF Display OFF Unit is in OFF state
Display ON Unit is in ON state
LED Flashing Unit is going through its Power-ON routine
LED ON Unit is in its STANDBY mode
When the unit is plugged into a power line, it will stay in the OFF state until the Standby button is
pushed. The LED will then start blinking and the unit will go through a 50second warm-up
sequence. At the end of that sequence it will turn ON.
Pressing the button again will switch the unit into its Standby mode.
The VK-31 can be turned OFF by pressing and holding the Standby button.
VK-31 Power-On sequence:
When you turn the VK-31 On, it will automatically go through a gentle power-on sequence. This
sequence takes 50 seconds, during which time the display and the Standby LED will be flashing,
indicating the status of the unit.
1. The number on the display during this time indicates the volume setting. This will usually
start at 000. This setting can be changed during this time by using the volume knob or
Volume Up/Down buttons on your VK-R3 remote control transmitter. In addition, such
functions as Phase, Mono, input selection and Mute can be changed during this time either
from front panel or through the remote control.
2. Normally the VK-31 will be not muted (Mute LED on the display is OFF) and will begin
playing at the end of the 50 second delay. If so desired, the unit can be put in the MUTE
mode during this delay interval either by depressing the front panel MUTE switch or by
using the MUTE button on the VK-R3 remote control transmitter.
Turning the VK-31 Off:
The unit can be turned OFF by pressing and holding the Standby button. It will automatically
mute.

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PHASE button and LED
This button allows the user to invert the absolute polarity of the signal to compensate for some
recordings that are made out-of-phase. The LED indicates whether the unit is in its INVERTING
or NONINVERTING mode. This function is also accessible via the VK-R3 remote control.
LED OFF Non Inverting operation
LED ON Inverting operation
MONO Button and LED
The Mono button allows the user to switch the VK-31 in Mono operation when the two channels
are summed together. This may be useful, for example, while listening to old monophonic
recordings. This function is also accessible via the VK-R3 remote control.
LED OFF Stereo operation
LED ON Mono operation
MUTE Button and LED
The Mute button disables the preamplifier output. It is recommended that the Mute be engaged any
time the signal cables are changed or any other system configuration changes are being made. This
function is also accessible via the VK-R3 remote control.
LED OFF Unit in Play mode
LED ON Output Muted
INPUT selection buttons 1through 5
These allow the user to select any of five available inputs to be played. The selected input number
together with its name will be indicated on the unit front panel display as well. This function is also
accessible via the VK-R3 remote control.
VOLUME Knob
This knob performs different function depending upon the unit’s mode of operation. In normal
mode it works as volume control knob.
It is also used as a data input device in various Function modes to program the unit. For example,
it is used to set the BALANCE adjustment when the VK-31 is switched into its Balance mode.
More on that in the corresponding sections of this manual.
The volume control knob on the VK-31 is linked to a digital encoder and is of a continuously
rotating type (there are no stops).

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DISPLAY FORMAT:
The VK-31 Vacuum Fluorescent Display (VFD) is capable of showing up to twelve alphanumeric
characters. Its format depends on the mode of operation. In the normal PLAY mode the display
has the following format:
1. One character indicating the selected input number.
2. Four-character input name. That name is fully programmable (See the programming
functions) and can include up to four character from the Latin, Cyrillic or Greek alphabets
or digits.
3. Balance adjustment indicator. Characters L or R indicate that the balance is shifted in the
corresponding direction. A BLANK character means that the gains of both channels are
identical.
4. Volume setting - three digits with the full range of 000 to 140 (See programming section on
Maximum Volume Setting)
FUNCTION Button
This button puts the unit in its programming mode. In addition to its normal PLAY mode, there are
eight programmable functions in the VK-31:
BALANCE Adjustment
RELATIVE VOLUME setting
PHASE setting
MONO/STEREO setting
MAXIMUM volume setting
FIXED volume setting
DISPLAY (Volume) mode
INPUT NAME assignment
Pressing this button while in PLAY mode will switch the unit into programming mode. Once in
the programming mode, pressing the Function button will switch the unit into its NEXT
programmable functions. The unit will stay in the programming mode until the exit command is
issued. To EXIT the programming mode at any time, press and hold the Function button for about
TWO seconds.

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DISPLAY ON-OFF Function
Changing the Display Brightness: The VK-31SE display can be dimmed or turned
completely OFF by simply pressing the DISPLAY button on your VK-R3 remote control
transmitter.
Each press will reduce the brightness of display and LED indicators in steps from full ON to
OFF, and then one press back to full ON. The LED indicators will dim but never turn
completely OFF. With the display OFF, issuing any remote control command that would
normally require a display change (i.e.: Volume, Input selection, Fade) will automatically
turn the display back ON for short period of time.
MUTE Function:
The VK-31 has two mute modes: manual and automatic. The blue LED above the Mute button
goes ON when the unit is in MUTE state. To MUTE the VK-31, depress the MUTE button located
on the right side of the front panel. Depressing this button again will return the unit to its normal
operation and turn the mute LED off.
When the unit is powered up it automatically self-mutes until the proper operating points of the
circuitry are reached. It will then automatically go into Play mode, provided the Mute function was
not activated (the blue Mute LED is Off).
Turning the VK-31 OFF even for short time, will make the unit reset its power sequencing circuit
and mute its output. It will then require 50 seconds for the unit to become operational again.

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VK-31 PROGRAMABLE FUNCTIONS
The VK-31 programming functions allow the user to optimize the unit configuration for any
particular system set up. The flexible programming facility defines each signal input with a group
of user-selectable parameters that are then stored in the unit’s memory. Every time a particular
input is selected, its unique combination of parameters is loaded into the operating memory.
Programming is easy and is accomplished through using just two front panel controls -: the
Function button and Volume knob, or corresponding remote control buttons (Function and
Volume Up/Down buttons).
Every unit comes from the factory with a default set of parameters stored in its memory. This set of
parameters is usable for many applications. The default set includes the following parameters:
BALANCE ZERO
RELATIVE VOLUME ZERO
PHASE Non-Inverting
MONO/STEREO STEREO
MAXIMUM VOLUME 140
FIXED GAIN OFF
DISPLAY COUNTS
INPUT NAMES 1 TAPE
2 TUN
3 CD1
4 AUX1
5 AUX2 or PH1 if the phono card is installed
The user may at any time, configure the unit to a particular set of system requirements. For
example, input names can be changed to reflect a given system’s source configuration.

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Parameter Definitions:
Every input of the VK-31 is defined with the following set of parameters.
1. Input name (Examples include CD1, DVD1, PH-1, VKD5, or any other combination of up
to four characters including the Latin, Cyrillic and Greek alphabet as well as digits)
2. Balance adjustment – gain shifted Left or Right.
3. Volume offset relative to any other input (to compensate for gross differences in various
sources levels)
4. Phase: Inverting, Non-inverting or Last configuration
5. Stereo, Mono or Last configuration
6. Maximum allowable volume setting for a particular input. This is a convenient safety
feature in some instances.
7. Display mode. This allows the user to switch the volume display to operate in any of the
three modes: relative Counts, DBU (Decibels referenced to Unity gain) or DBM (Decibels
referenced to Maximum gain).
8. Fixed volume mode: this allows any input to be set with a preferred fixed volume setting,
and is usable, for example, in Audio/Video installations.
With this flexibility it is possible, for example, to set the CD input to be Stereo and Non-Inverting,
while the Phono input would be Mono and Inverting.
PROGRAMMING THE VK-31
NOTE: It is important to note here that all the functions described below are accessible
either through the front panel controls or via the VK-R3 remote control. Therefore,
functions like BALANCE, PHASE, MONO, etc. all can be performed by using the Function
button on the remote control in conjunction with the Volume Up/Down buttons.
BALANCE Adjustment.
Pressing the Function button once will invoke the Balance adjustment mode. When in this mode,
turn the volume control knob (or press the Volume Up/Down buttons on the VK-R3 remote
control) to set the balance to the desired position. An L or R character will appear indicating that
the balance is now shifted in the corresponding direction.
Exiting the programming mode by pressing and holding the Function button will store this
adjustment for the selected input.
The BALANCE adjustment for each selected input is also stored when switching to another input
while still in the BALANCE programming mode.

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RELATIVE Volume adjustment.
It is quite common to have sources with very different output levels connected to a preamplifier. In
this case, switching between different inputs is usually accomplished by a large change in volume.
The VK-31 allows the user to avoid this inconvenience by setting volume offsets between different
inputs (using ANY input as a reference).
To program this feature:
1. Select any input that you would like to use as a reference. Play music at the level you find
comfortable.
2. Press the Function button twice. The display will read: VOL 000
3. Switch to a different input. Adjust the volume while playing the music to the level that is
comparable to the reference input level. The display will indicate the volume offset
number. That number can be either positive or negative, depending upon whether the new
selected input is stronger or weaker than the reference input.
4. Exit the programming mode by pressing and holding the Function button or by switching
to a different input.
Any input volume offset can be programmed at ANY time with respect to ANY other input.
EXAMPLE:
The CD1 input is used as the reference. Let’s presume that the PH1 input (the weaker source) is
then programmed to play at 20 counts higher. Its volume offset will then read 20.
The user can later select the PH1 input and using it as the reference, program the AUX1 input to be
10 counts lower than the PH1 input. Effectively, the volume offset from the CD1 input to the
AUX1 will now become 10.
The user then can at any time verify his volume offset programming by switching the unit in its
VOLUME mode (by pressing the Function button twice) and then selecting the inputs 3, 4 and 5.
The volume offset numbers for these inputs should then read 0, 10 and 20 respectfully. That means
that the AUX1 source will be played at 10 counts above the CD1 input and the PH1 input at 20
counts above the CD1 input.
Alternatively, the volume offset number can be entered directly, based on your judgement of
volume difference between the two sources. To do that, select the input, enter the VOLUME
programming mode by pressing the Function button twice, and use the volume knob to set the
volume offset number that you deem desirable. Then exit the programming mode by pressing and
holding the Function Button.
NOTE: A negative number for the selected input indicates that its gain will be set lower than
the gain of the reference input.

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PHASE programming.
Select the desired input.
Press the Function button three times. The display will read: PHASE NINV.
Use the volume knob to set the condition to NINV, INV or LAST.
Exit the programming mode by pressing and holding the Function button.
NOTE: In the LAST mode, the state of the PHASE switch will be the same as used the last
time for that particular input.
MONO/STEREO programming.
Select the desired input.
Press the Function button four times. The display will read: STEREO
Use the volume knob to set the condition to STEREO, MONO or LAST.
Exit the programming mode by pressing and holding the Function button.
NOTE: In the LAST mode, the state of the Phase switch will be the same as used the last
time for that particular input.
MAXIMUM gain programming
It may be desirable to limit the allowable volume setting on a particular input. To do this:
Select the desired input
Enter the MAXIMUM programming mode by pressing the Function button five times.
Set the display to any desired number that will now represent the maximum allowable
volume setting for the selected input.
Exit the programming mode by pressing and holding the Function button.

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FIXED Gain mode
In some systems (some A/V installations, for example) it is desirable to set a particular input to a
fixed gain, that is then becomes unaffected by the volume knob. Most often it is required to set the
preamplifier gain to Unity (Gain of 1). The VK-31 allows the user to do so by using its FIXED
gain function.
Press the Function button six times.
The display will read: FIX OFF
Enter any desired number for the fixed gain on the selected input (see below).
UNITY gain for the VK-31 preamplifier correspond to the following volume setting:
CNTS display mode 100 Counts
DBU 00.0dB
DBM -20.0dB
Exit the programming mode by pressing and holding the Function button.
DISPLAY MODE programming
The volume display of the VK-31 can be switched to work in any of the following three modes:
CNTS: Relative volume counts with the range of 000 to 140
DBU: Decibel readings with respect to unity gain (0dB).
DBM: Decibel readings with respect to maximum gain (20dB)
NOTE: To avoid possible confusion, the SAME display mode setting applies to ALL inputs.
It is not possible, for example, to set one input to CNTS and another to DBU.

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INPUT NAME programming:
The VK-31 allows the user to assign any a custom name to any input. Those names may include up
to four characters. The default names for the inputs are as follows:
1 TAPE
2 TUN
3 CD!
4 AUX1
5 AUX2 (It will automatically switch to PH1 if the optional phono card is installed)
Any combination of up to four Latin, Cyrillic, Greek alphabet characters or digits can be used to
name the source. The examples may include:
CD-2, DVD1, JOHN, VKD5, MARY, BOB1, etc.
To program the input name, do the following:
Select the desired input
Press the Function button eight times. The first character of the input name will start blinking
Use the volume control knob or the remote control Volume Up/Down buttons to select the
desired character. The characters are organized in the following order: the digits, the Latin
alphabet, the Cyrillic (Russian) alphabet, the Greek alphabet.
Advance to the next character by pressing the Function button once.
Exit the programming mode by pressing and holding the Function button.

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REMOTE CONTROL FUNCTIONS:
The optional VK-R3 remote control that comes with your VK-31 has the following functions:
Volume Up and Volume Down control
Mute function
Fade Down/Fade Up function
Input source selection 1 through 5
Phase switch
Function switch
Display/POWER switch.
The following describes these functions.
Volume Up and Down
These two buttons are programmed with variable speed volume change profiles. The rate of
volume change will be slow upon initial pressing of the Volume Up or Down buttons. Holding the
button depressed will cause the rate of change to accelerate, allowing for more flexible control
when large changes in volume are required.
Mute
Pressing this button will cause the MUTE function in the VK-31 to toggle between ON and OFF
states. The Mute LED on the VK-31 front panel will reflect the status of the Mute circuit.
Fade
Pressing the FADE button on the VK-R3 remote control will cause the volume to smoothly decay
over the period of several seconds. This allows for a gradual reduction in volume, as opposed to
the instantaneous MUTE function. This can be particularly useful during the presentation or
demonstration of your equipment. When the FADE button is pressed, the volume will go down all
the way to zero (000 on display, unit in Mute).
Pressing the Fade button again will cause the volume to ramp back up to its initial value.

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INPUT SELECT:
Pressing any input selection button on the VK-R3 remote control will switch the VK-31 to that
input. All of the set parameters associated with that input will be loaded at this point.
DISPLAY/POWER switch.
The Display/Power button on the VK-R3 remote control provides two functions: turning the VK-31
display ON/OFF and switching the power to the preamplifier.
To control the display:
Pressing the display button will switch the display from ON to OFF and back.
Turning the VK-31 OFF
With the display in ON state, press and hold the Display button on the VK-R3 remote
control. This function is disabled when the unit’s display is turned OFF.
Turning the VK-31 ON
With the VK-31 in its OFF or STANDBY state, simply press the POWER button on the
VK-R3 remote control transmitter.
Fuse Protection:
A blown fuse in the VK-31 is an indication of a serious problem. If a replacement fuse fails as
well, no further attempts should be undertaken. Please contact the factory for professional service.
The proper fuse ratings are as follows:
For 100-120 VAC Units: 2A 250V Slow Blow
For 200-240 VAC Units: 1.5A 250V Slow Blow
Factory supplied fuses should be only replaced with the same type and rating parts.
Servicing
The Balanced Audio Technology VK-31 should require no service in normal operation. Please
direct any further service inquiries to the factory.
Cleaning
To remove dust, occasionally wipe the front and top surfaces of your VK-31 with a damp soft cloth.
If fingerprints appear, you may use a mild, non-alkaline soap solution. Do not use abrasive
cleaners, as they may damage the fine finish of the unit.

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Five Year Limited Warranty
Terms and Conditions
1. Limited Warranty
Upon receipt of the attached warranty registration form, Balanced Audio Technology warrants the purchased
product to be free from manufacturing, materials, and workmanship defects for five years from date of original
purchase, excepting vacuum tubes, subject to the following conditions. Failure to return the enclosed
registration form within 30 days from original purchase will result in a warranty period of one year from
the date of manufacture.
2. Vacuum Tubes
Vacuum tubes (including replacements under warranty) are warranted for one year from the date of the original
VK-31 purchase.
3. Limited to Original Purchaser
This warranty is for the sole benefit of the original purchaser of the covered product, and may not be transferred
to a subsequent purchaser of the product.
4. Conditions and Limitations
This warranty is subject to certain conditions and limitations, as follows. This warranty is void and inapplicable
if the product has not been used in accordance with the instructions found elsewhere in this manual, or if it has
been misused or abused, damaged by accident or neglect, or in transport once in possession of the purchaser.
The warranty is also void if the product has been repaired, modified, or tampered with by anyone other than
Balanced Audio Technology or its specifically authorized agents.
5. Remedy
If this product contains a materials, manufacturing, or workmanship defect that cannot be repaired at the
dealership where the product was purchased, it must be packed in original packaging and returned to Balanced
Audio Technology via insured freight, at the owners expense. If replacement packaging materials are required,
they will be supplied by the factory at a nominal charge. Returned products must be accompanied by a
written description of the defect, and a return authorization number (available from the factory via
phone or fax). Upon receipt of defective product, Balanced Audio Technology agrees to repair the product
without charge for parts (except vacuum tubes if the unit is more than one year old), or labor. The product will
then be returned via prepaid, insured freight, with carrier at the sole determination of Balanced Audio
Technology. This constitutes the purchasers sole remedy.
6. Design Changes
Balanced Audio Technology reserves the right to modify its products or change specifications at any time
without obligation or liability to previous purchasers.
7. Miscellaneous
Any implied warranties relating to the above product shall be limited to the duration of this warranty. This
warranty does not extend to any incidental or consequential costs or damages to the purchaser. This warranty
gives you specific legal rights. You may also have other rights which vary from state to state.