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connecting balanced sources
You may run into a situation where you need to take a +4dB
balanced line-level source and convert it to a mic-level.
This is particularly important in snake systems where the
signal path is optimized for a microphone between -40dB
and -20dB. If one were to connect a +4dB signal, the mic
splitting transformers would likely overload and crosstalk
would likely be introduced due to the +4dB line-level signal
being signifi cantly louder than the mic-level signal.
To address this situation, each Duplex channel is
equipped with a female XLR input labeled LInE-In that
is pre-padded to bring a +4dB level down to mic-level. To
use the XLR LInE-In set the XLR sEL switch to it's inward
position. The switch is recessed to prevent accidental use.
a small screwdriver can be used to access the switch.
When the balanced XLR input is active, the ¼", RCa and
3.5mm input jacks are disabled.
BALANCED
LINE-LEVEL
CHANNEL-2
MIC-LEVEL
Radial Engineering Ltd.
PA SYSTEM
CHANNEL-1
MIC-LEVEL
using the -15db pad
occasionally you may be confronted with a super
powerful source that could overload and saturate the
transformers inside the Duplex. This could, for instance,
be the output signal from a DJ mixer. If this scenario
presents itself, depressing the -15dB PaD switch
reduces the input sensitivity and cleans up the signal.
If you hear distortion, set the PaD switch to it's inward
position. You may have to increase the input level at the
mixing desk to compensate.
180° polarity reverse
There are two primary reasons to have a 180° polarity
reverse on a direct box. The fi rst has to do with ensuring
the electrical phase of the DI is in line with the equipment
in use. some older audio systems employed pin-3 on
the XLR as the hot output before the aEs standard (pin-
2 hot) was universally adopted.
The second has to do with the audible phase problems.
For instance, in a small club, when combining a direct
feed from a bass guitar and bass amplifi er with the
sound of the Pa, you may fi nd that the two signals are
competing with each other causing phase cancellation
at the mix position. By reversing the phase on the direct
signal, the problem can be reduced. If using the Duplex
with an acoustic guitar, a similar problem could occur
whereby the sound from the stage monitors could
7
True to the Music
JDI • Duplex User Guide
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