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21.2 Line Out TRS 1/2
The ADI-2/4 Pro SE has two impedance balanced, short-circuit protected analog Line outputs that
can operate with levels up to +21.5 dBu (Ref Lev +19 dBu with Volume set to +2.5 dB). Using a
stereo (TRS) jack the output uses two 100 Ohm resistors internally to achieve impedance balanc-
ing. Using an unbalanced mono (TS) jack ring is connected to ground automatically, the output
then operates unbalanced.
These outputs follow all Ref Lev settings, but stay at +19 dBu when +24 dBu is selected. For
Auto Ref Level see next chapter.
21.3 Line Out XLR 1/2
The ADI-2/4 Pro SE has two balanced analog outputs that can operate at levels up to +26.5 dBu
(Ref Lev +24 dBu with Volume set to +2.5 dB). The short circuit protected, low impedance line
outputs 1/2 are available as XLR jacks on the back of the unit.
The XLR line outputs do not operate servo balanced! When connecting unbalanced equip-
!
ment, make sure pin 3 of the XLR output is not connected. A connection to ground might
cause a decreased THD (higher distortion) and increased power consumption!
To maintain an optimum level for devices connected to the analog outputs, the ADI-2/4 Pro SE
internally uses hi-quality electronic switches, which allow for a perfect adaptation to the most
often used studio levels.
The analog outputs 1/2 (and 3/4) also feature a mechanism to set the reference level automati-
cally. Auto Ref Lev(el) maximizes the signal to noise ratio when using the Volume knob. It
changes to the next higher and lower reference level setting when the gain chosen via the Volume
knob would suggest to set a better fitting value, with optimized signal to noise ratio.
Example: Ref Lev is set to +24 dBu, Volume is set to -21 dB. The effective signal to noise ratio at
the XLR output is now 120 dB minus 21 dB = 99 dB (RMS unweighted). While it is unlikely that
any noise will be audible, changing the Ref Level to +7 dBu would need only a Volume setting of
-4 dB. The effective SNR then becomes 120 minus 4 = 116 dB. Such settings are usually done
manually by the user. Auto Ref Lev takes over this task, working in both directions when turning
Volume up or down.
Notes: This technique includes switching of hardware elements (like when doing it manually) and
is therefore not free of click noise. To prevent distortion the threshold for a Ref Level change takes
EQ gains into account.
21.4 PH Out 1/2
Channels 1/2 are also available on the front as 1/4" TRS (stereo) jack.
All outputs labelled 1/2 share the same Volume knob setting, but Ph 1/2 has its own, independent
hardware Ref Levels (IEM, Low and High Power). Also as mentioned above the rear TRS output
is capped to +19 dBu.
Please note that PH 3/4 is the main phones output of the ADI-2/4 Pro SE. PH 1/2 is designed as
addition and extra functionality. Sharing volume/level settings with the rear outputs some limita-
tions arise. PH 1/2 is simply not totally independent, and should therefore only be used when
really needed. The ADI-2/4 Pro SE issues a warning message when inserting a plug into PH 1/2.
User's Guide ADI-2/4 Pro SE – v 1.0
53
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