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18. Balanced Phones Mode
In balanced operation, two identical power amplifiers are used to drive one side of the phones
each. Compared to normal, grounded operation, the voltage seen by the phone driver/speaker is
doubled. The power sent to it is even quadrupled.
With the comparatively low power required by headphones, and its already powerful Extreme
Power outputs, the balanced phones mode of the ADI-2/4 Pro SE has not been optimized for
more power, but more fidelity. See chapter 34.6 for all the details behind the True Balanced mode
implemented in the ADI-2/4 Pro SE.
In True Balanced mode the ADI-2/4 Pro SE's maximum output level rises to +7 dBu for IEM, +13
dBu for Low Power, +25 dBu for High Power. The signal to noise ratio stays unchanged. See
chapter 34.18 for details about the available output power at the phones outputs.
Balanced Phones mode requires headphones with separate cabling for left and right channel, 2
wires each, 4 wires in total.
Output PH 3/4 becomes the left channel out-
put, with former left channel as L+ and former
right channel as L−. PH 1/2 becomes the
right channel output, with former left channel
as R+ and former right channel as R−. Gnd
of both connectors stays unconnected.
There exist different solutions on how to con-
nect balanced phones, but no standard as
such.
The use of a 4-pin XLR male connector on
the phones side is quite popular. The diagram to the right shows how an adapter cable can be
used to connect the ADI-2/4 Pro SE phones outputs, using two stereo TRS plugs and one female
XLR connector.
See chapter 14.1.3 on how to activate Balanced TRS Phones mode.
When using the Pentaconn socket, the unit automatically switches the output channel Phones 3/4
to Balanced mode.
Note: When using the Pentaconn jack, the balanced signal is also present at both Ph TRS. The
use of a second, unbalanced headphone via TRS is not possible, as the signal of both TRS sock-
ets represents only one channel each.
User's Guide ADI-2/4 Pro SE – v 1.0
47
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