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.