INTRODUCTION
UNPACKING
Thank you for selecting the US Audio DA-2. The DA-2 is a
2- channel, line-level, audio signal distribution amplifier.
Each channel provides four electronically balanced XLR
outputs with individual volume controls. The audio
performance is of the absolute highest quality possible and
at a reasonable price point, making it an excellent value.
Great care was taken in the design so that the DA-2 can
fulfill any distribution requirement, from professional disk
and tape duplication to power amp input distribution. With
the impedance of the active balanced XLR inputs set at
1Meg Ohms, several units can be paralleled for virtually
unlimited outputs. The DA-2 can provide up to 18dB of
gain allowing operation as a -10dB to +4dB converter.
Other features include clip and signal LEDs, a headphone
monitor circuit and a “combine” switch which configures
the DA-2 as a one by eight distribution amp.
US Audio has made every effort to ensure that your
equipment is received in the same perfect condition it was
in when it left the factory. Please inspect your product for
any signs of damage during shipping and report them to
your dealer so that he can present a claim to the shipper.
We recommend that you save your packaging material for
use in the unlikely event that you need to return your
equipment for service.
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CONTROLS AND CONNECTIONS
1. Output Volume Pots control the level at the
corresponding rear panel output XLR. Each of the controls
has a gain range of -60dB attenuation at full off to + 18dB
of gain at full on.
7. Power Switch connects AC to the transformer primary
and the LED indicates that the unit is working. Both sides
of the AC line are switched and a mains fuse is located on
the circuit board inside the unit.
8. Output XLR5 on the DA-2 are actively balanced with
the audio ground lifted (pin 1 disconnected). If grounding
pin 1 of the XLR is required, there is a spot for a jumper for
each XLR output on the PC board. Each output is driven
with its own individual driver circuit providing channel-to-
channel isolation greater than 74dB. The outputs are wired
pin-2 positive, pin-3 negative and are RF-bypassed with
capacitors for rejection of RF signals on the output lines.
2. Individual Clip LEDs on all 8 outputs and on each of
the two inputs indicate signal overload conditions within
the circuitry. The red clip lights illuminate at 3dB below
actual clipping (the unit clips at ±28dB balanced, the LEDs
illuminate at +25dB).
3. Signal Present LEDs on each of the input channels
indicate that signal is being applied to the input. The green
lights illuminate when the input signal is greater than
-14dB balanced or -20dB unbalanced.
9. Input XLR Connectors feed actively balanced
differential amplifiers providing over 90dB of common
mode rejection. The input impedance is factory-set at 1Meg
Ohms, allowing the inputs of many units to be paralleled
together. If lower input impedance is desired it can be
easily accomplished by an internal resistor change. In
Combine mode inputs 1 and 2 are actively summed to
mono. Pin-2 is positive, pin-3 negative and pin-1 is
connected to audio ground.
4. Combine Switch converts the DA-2 from a 2 by 4
configuration to a 1 by 8 distribution amp. In this mode the
two inputs are actively mono-summed or either input may
be used to feed the eight outputs. The mono-sum feature
allows the DA-2 to properly combine left and right stereo
signals into a mono feed.
5. Channel 1/2 Select Switch determines which channels
10. Ground Lift Switch connects the audio circuit ground
input signal is fed to theheadphone circuit for monitoring.
to AC ground and the chassis of the unit, if desired.
6. Headphone Circuit monitors the signals coming into
the DA-2 inputs. It is a mono circuit which drives both
earpieces in stereo headphones that have an impedance
greater than 20 Ohms.The volume control has a gain range
of -60 to +18dB to accommodate a wide range of audio
levels. The jack is a standard 1/4” TRS type.
11. Power Cord - a standard 15 amp plug for l20VAC and
has no plug on the DA-2X 230VAC model. Black is line,
white is neutral and green is earth.
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SPECIFICATIONS
Frequency response
± .3dBm 20 to 20KHz
± 3dBm 3 to 140KHz
Added noise of dual
channel mode
+2dBm
Input impedance
Max. input level
1Meg Ohm balanced
C.M.R. of inputs 20-20kHz >9OdBm
+23dBm unbalanced
+28dBm balanced
Range of headphone
volume control
-60 to +l8dBm
Output impedance
Max. output level
T.H.D.
112 Ohm balanced, ground
lifted
Isolation between outputs >74dBm
Power Consumption
@120VAC
.15 Amps max. A.C.
+22dBm unbalanced
+28dBm balanced
.15 Amps max. A.C.
@230VAC
.004% at 1kHz.
<.005% 20-20kHz
AC Dropout Voltage
+105 VAC @ l20VAC
+205 VAC @ 230VAC
Rise time
3uSec
Phase shift
.5 degree at unity gain
Internal Mains Fuse
.25 Amps Slo-Blo 3AG
Intermodulation distortion .007% at unity gain
Size (Single Space Standard E.I.A. Spec)
19.0” (482.6mm) Width
Signal present threshold
LED Clip Threshold
-20dBm unbalanced
-l4dBm balanced
6.0” (152.4mm) Depth
1.75” (44.45mm) Height
+l9dBm unbalanced
+25dBm balanced
Shipping Weight
Unit Weight
8.0 lbs (3.63kg)
6.5 lbs (2.95kg)
Output signal range level -60 to + l8dBm
Equivalent Input Noise and Signal to Noise Ratio
whirlwind / U.S. Audio
99 Ling Road Rochester NY 14612
800 733-9473 585 663-8820 585 865-8930 Fax
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