Whirlwind Stereo Amplifier DA 2 User Manual

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.  
 
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.  
 
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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