Balanced Audio Technology REX User manual

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REX
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 Stat Blvd. Suite A Wilmington DE 19804 Tel: [phone] Fax: [phone]

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REX
Vacuum Tube
Balanced Stereo Preamplifier
Owner's Manual
1300 First Stat Blvd. Suite A Wilmington DE 19804 Tel: [phone] Fax: [phone]

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TABLE OF CONTENT
CURRENT SOURCES 4
CHANGING CURRENT SOURCES 5
AC SHUNT VOLTAGE REGULATORS 6
INTRODUCTION 7
Package Content 7
Physical Placement 8
Configuring the REX 8
Connecting to your system 9
FRONT PANEL CONTROLS 10
REX Power On sequence 10
Turning the REX Off 10
PHASE Button and LED 11
MONO button and LED 11
MUTE button and LED 11
INPUT selection 11
VOLUME knob 11
DISPLAY format 12
FUCTION button 12
DISPLAY Brightness function 13
MUTE function 13
REX PROGRAMMABLE FUNCTIONS 14
Parameter Definitions 15
PROGRAMMING THE REX 15
BALANCE adjustment 15
VOLUME offsets 16
PHASE 17
MONO/STEREO 17
MAXIMUM gain 17
FIXED gain 18
DISPLAY MODE 18
INPUT NAME 19
REMOTE CONTROL FUNCTIONS 20
Volume Up/Down 20
Mute 20
Fade 20
Input 20
Display/Power 21
Fuse Protection 21
Servicing 21
Cleaning 21
RESETTING THE REX 22
WARRANTY 23

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Vacuum Tube Current Sources in REX
Your REX incorporates a unique feature that allows you to optimize its sound to tailor it to your
individual taste or system requirements.
The Vacuum Tube current sources incorporated in the REX, being part of the signal gain stage, have a
direct effect on the unit’s sound. Changing the tube type used in that circuit allows the user an extra
degree of control over the sound of the unit.
In its standard configuration the REX current sources use the Russian 6C19 tubes. That tube is basically
a miniature version of the famous 6C33 tube, and provides, in our view, the best combination of sonic
characteristics and electrical performance.
However, the unique design of the REX allows you to also use other tube types in that application.
Currently, the user has the following three choices for vacuum tube Current Sources:
1. The standard 6C19 tube current source as installed from the factory.
2. The 6H30 SuperTube current source which requires the purchase of the X-PAK accessory.
3. The 5881 tube current source.
NOTE: There are TWO Current Sources in REX, located in the Power Module.
The REX X-PAK accessory includes two current source boards.

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In order to change the tube type the user needs to remove the installed Current Source boards, and replace
them with either another type, designed for a particular tube type, or install the 5881 tubes as a direct plug-in.
Only the 5881 tubes can be used directly upon the removal of the 6C19 current source board.
Please consult the factory regarding options for other tube types that may be available in the future.
WARNING:
The following procedure should only be performed by qualified personnel
To change the current source:
1. Turn the unit OFF and wait at least 5 minutes to allow the tubes to cool down and the power
supply charge to dissipate. Remove the Power Module top cover.
2. Remove the six screws holding each current source board.
3. Pull the current source boards straight up to disengage its connectors.
4. Install the new current source boards making sure their connectors are properly aligned. Boards
will be positioned properly when the mounting holes in the circuit boards align with the standoffs.
5. Install the six mounting screws.
6. Turn the unit ON.

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AC SHUNT VOLTAGE REGULATORS
The REX preamplifier incorporates another feature that allows the user to optimize its sound – the
AC Shunt voltage regulators.
The AC Shunt voltage regulators perform the final “cleaning” of the REX power supply rails. They
work to reduce the minute fluctuations in the DC voltages that may degrade the sound.
The AC Shunt Voltage Regulators are located in the REX Power Module.
They incorporate two types of vacuum tubes, user selectable for the desired sound: 6C45 and 6H30.
To change the AC Shunt tube type remove the Power Module top cover and move the board-mounted
switch S1 to desired position. The switch is located close to the center of the board.
Only the selected tubes will have their filaments running at any time.

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INTRODUCTION
Thank you for your purchase of the Balanced Audio Technology REX preamplifier. Please
read this owner's manual to obtain the full benefit of the REX 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 set should be the following:
Description Quantity
REX Control Module 1
REX Power Module 1
Power Cord 2
Spare Fuse 2
Torx Wrench (T-10) 2
Spare Top Cover Screws 10
User’s Manual 1
VK-R3 Remote Control (If ordered)

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Save all the packaging material in a safe dry area for the unlikely event that you need to return
the REX to the factory for service.
PHYSICAL PLACEMENT
It is recommended that you provide at least 6" of free space around each module comprising the REX
preamlifier for proper ventilation.
Mount the modules on a hard surface with proper ventilation underneath.
Do not stack the REX preamplifier on top of other units, nor vice versa.
WARNING
Stacking the modules (putting the Control Module on top of the Power Module)
is NOT permitted.
CONFIGURING THE REX PREAMPLIFIER SYSTEM
The REX preamplifier system consists of two modules.
Control Module performs all the control functions associated with the duties of the
preamplifier in your system. It also receives and processes the remote control commands.
Power Module works in conjunction with the Control Module as an outboard power supply.
The two modules are connected by two detachable cables. In addition each module has its own
power cord that must be plugged into the power outlet.
WARNING
Make sure your REX is powered DOWN before making or changing ANY
connections between its two modules, to the source components or power
amplifiers.
Connect the two detachable cables between the modules, making sure the channels are connected
properly.
Plug the two power cords into power receptacles.
Make all the signal connections.

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CONNECTING THE REX TO YOUR SYSTEM
Balanced Components
Use balanced XLR interconnects. All input and output connectors are clearly marked on the back
panel.
Note: The REX XLR connectors are wired as follows:
Pin 1: common/shield
Pin 2: positive
Pin 3: negative
For the REX, 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 REX preamplifier is designed to work
with balanced interconnects only. If single ended components need to be connected to the
preamplifer, then the RCA/XLR adapters should be used. 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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REX 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 REX can be turned OFF by pressing and holding the Standby button.
REX Power-On sequence:
When you turn the REX 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.
In addition, the blue LED on the Power Module front panel will also light.
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 REX 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 REX 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 REX 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 REX is switched into its Balance mode. More on
that in the corresponding sections of this manual.
The volume control knob on the REX is linked to a digital encoder and is of a continuously rotating
type (there are no stops).

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DISPLAY FORMAT:
The REX 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 REX:
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 Brightness Function
Changing the Display Brightness: The REX 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.
MUTE Function:
The REX 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 REX, 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 REX 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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REX PROGRAMABLE FUNCTIONS
The REX 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 REX 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 REX
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 REX 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 REX 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 REX 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 REX 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 REX 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 REX 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 REX to toggle between ON and OFF states.
The Mute LED on the REX 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.
INPUT SELECT:
Pressing any input selection button on the VK-R3 remote control will switch the REX to that input.
All of the set parameters associated with that input will be loaded at this point.