Mic/Line Inputs; Line Outputs - RME Audio OctaMic User Manual

6.2 Mic/Line Inputs

The OctaMic offers 8 balanced Mic and Line inputs via 1/4" TRS (stereo) and XLR combo
jacks. The electronic input stage is built in a servo balanced design which handles monaural
and stereo jacks correctly. When used unbalanced it automatically corrects the gain by 6 dB.
When using unbalanced cables with stereo TRS jacks, the 'ring' contact of the cable's jack
should be connected to pin 1 (ground). Otherwise noise may occur, caused by the uncon-
nected negative input of the balanced input.
The pinout follows international standards. XLR pin 2 + or hot, pin 3 – or cold, pin 1 ground.
TRS tip + or hot, ring – or cold.

6.3 Line Outputs

The 8 short circuit protected, low impedance and servo balanced line outputs are available as
(stereo) 1/4" TRS jacks. The electronic output stage is built in a servo balanced design which
handles monaural and stereo jacks correctly. When used unbalanced it automatically corrects
the gain by 6 dB.
The pinout follows international standards. TRS tip + or hot, ring – or cold.
To maintain an optimum level for devices connected to the analog outputs, the OctaMic in-
cludes a switch which allows to change the reference level of all 8 outputs simultaneously.
The OctaMic can generate a maximum level of +21 dBu without distortion. However, the CLIP
LED has been designed to act like the OVR LEDs of the ADI-8 series. It lights up 2 dB before
the reference level selected on the back of the unit, plus a headroom of 9 dB, is reached. At Hi
Gain the LED lights up at +17 dBu output level, selecting +4 dBu it lights up at +11 dBu, select-
ing –10 dBV it lights up at 0 dBV.
Setting Reference Clip LED
Hi Gain +19 dBu
+4 dBu +13 dBu
-10 dBV +2 dBV
This also means that the CLIP LED lights up 4 dB before the OctaMic actually reaches the
maximum level. Such an additional headroom is considered to be useful in real world opera-
tion.
The chosen reference level has no meaning for the ADC module. The ADC modul is designed
for a level of –2 dBFS as soon as the Clip LED lights up.
Selecting +4 dBu the output signal is attenuated by 6 dB, so for the same output level the am-
plification has to be increased via GAIN. With this trick the OctaMic reaches the maximum
signal to noise ratio on +4 dBu based inputs (like our ADI-8 series), because microphone pre-
amps have better EIN values at higher amplification. In case of an extreme recording situation,
where the gain of the OctaMic is no longer sufficient, selecting Hi Gain will again provide the
highest amplification possible.
The same is true and even more efficient at –10 dBV. In this case the output level is reduced
by around 14 dB – the same happens to the basic noise of the unit!
True Clip
+17 dBu +21 dBu
+11 dBu +15 dBu
0 dBV +4 dBV
User's Guide OctaMic © RME
ADC Level
-2 dBFS
-2 dBFS
-2 dBFS
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