RDL STUBA2 Installation Guide

STICK-ON® SERIES

Model ST-UBA2
Unbalanced to Balanced
Amplifier

ANYWHERE YOU NEED...

• To Convert Stereo IHF Levels to Stereo
PRO

• Additional MONO Sum Output

• Independently Adjustable Gain

• Ground-referenced Conversion Module

• LED VU Metering for Each Channel

• Unparalleled Audio Performance

You Need The ST-UBA2!

The ST-UBA2 is part of the group of versatile STICK-ON products from Radio Design Labs. STICK-ONs
feature the advanced circuitry for which RDL products are known, combined with unequalled versatility in
mounting possibilities. The durable adhesives provided with the ST-UBA2 permit permanent or removable
mounting. Numerous available mounting accessories, brackets and rack-mount chassis are optionally available
to facilitate any system design.

FUNCTIONAL DESCRIPTION: The ST-UBA2 is a dual channel line-level device with separate left (L) and
right (R) inputs. Each input is unbalanced and is designed to accept input signals from -20 dBV to -10 dBV.
A-multi-turn gain potentiometer is provided for setting the level independently for each input. The unbalanced
signals are converted to balanced signals in the module. The balanced line amplifiers provide low impedance,
balanced +4 dBu outputs. In addition to the LEFT and RIGHT outputs, a third MONO output is provided. This
balanced output is the sum of the left (L OUT) and right (R OUT) balanced outputs. The mono output is 6 dB
below each of the individual channel outputs thereby producing identical levels at all three outputs when the
inputs are fed with in-phase signals.

Separate LED level metering is provided for the left and right outputs. Each channel is equipped with two
LEDs. A green LED illuminates at 15 dB below +4 dBu. The intensity of the green LED progresses from
minimum at -11 dBu to full intensity at +4 dBu. The adjacent red LED illuminates at +4 dBu. This two-LED
meter provides a compact, accurate indication of dynamic audio. The ballistics of the metering circuit follows
the same rise and fall times of a standard VU meter. Therefore, the audio may be adjusted for maximum
intensity of the green LED. Flashing of the red LED is equivalent to a VU meter needle swinging above the “0”
level. The meter is calibrated to the standard operating level of +4 dBu.

Module operation is from a 24 Vdc ground-referenced power supply.
TYPICAL APPLICATION: The ST-UBA2 is used in any application requiring conversion from unbalanced

consumer format signals to professional +4 dBu. It may be used to balance audio from CD players, cassette
decks, computer sound cards, televisions, and a wide variety of other unbalanced sources. The mono sum
output may be used to drive patch-bay jacks, monitors or subwoofer amplifiers.

The audio clarity, low noise, low distortion and excellent crosstalk performance makes this module ideally
suited to a wide variety of demanding audio applications. Use this module in conjunction with other RDL
modules as part of a high quality, flexible audio/video system.

RDL • 659 N. 6th St. • Prescott, AZ., USA 86301 • [phone] • FAX [phone] • www.rdlnet.com

STICK-ON® SERIES

Model ST-UBA2
Unbalanced to Balanced Amplifier

PWR

R

24 VDC

POWER

SOURCE

STEREO SIGNAL

FROM

UNBALANCED

LINE-LEVEL

SOURCE

Typical Power

Connection to a

PS-24A, PS-24E,

PS-24K, or PS-24U2A

Power Supply

GAIN ADJUSTMENT

25-TURN POT

GAIN

G
A

I

N
L

+

INPUTS -20 TO -10 dBV OUTPUTS +4 dBu

INPUTS

PWR

L

R

L OUT R OUT

MONO OUT

Installation/Operation

EN55103-1 E1-E5; EN55103-2 E1-E4

Typical Performance reflects product at publication time
exclusive of EMC data, if any, supplied with product.
Specifications are subject to change without notice.

ILLUSTRATION

SHOWING RIGHT

CHANNEL VU

G
A

I

N
R

GAIN

INDICATORS

(IDENTICAL SET ON

LEFT SIDE)

15 dB below +4 dBu
Output (Green LED)

GAIN ADJUSTMENT

+

25-TURN POT

+4 dBu Output (Red LED)

MONO

SIGNAL

FEEDING

BALANCED
LINE-LEVEL
EQUIPMENT

STEREO SIGNAL

FEEDING

BALANCED

LINE-LEVEL
EQUIPMENT

TYPICAL PERFORMANCE

Inputs (2): Unbalanced line level
Input Impedance: 10 kΩ
Input Signal Range: -20 dBV to -10 dBV
Outputs (3): +4 dBu balanced (left, right, mono sum)
Gain: 2 dB to 22 dB Adjustable
THD+N: < 0.02% (20 Hz to 20 kHz)
Freq. Response: 20 Hz to 20 kHz (+/- 0.2 dB)
Noise: < -85 dB (referred to +4 dBu)
Indicators (4): 1 green LED per channel indicating 15 dB range below +4 dBu Output Level
1 red LED per channel indicating +4 dBu Output Level
IMD: < 0.004%
Crosstalk: < -75dB @ 1 kHz
< -60dB @ 10 kHz
Headroom: > 18 dB above +4 dBu
Power Requirement: 24 to 33 Vdc @ 75 mA, Ground-referenced

Radio Design Labs Technical Support Centers

U.S.A. [phone], [phone]; Fax: [phone]

891-1035C

Europe [NH Amsterdam] (++31) 20-6238 983; Fax: (++31) 20-6225-287