RME Audio DMC-842, Руководство пользователя

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User’s Guide DMC-842
© RME
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9.4 Mode 2
In Mode 1 the digital microphone is clock master, operating from the internal and fixed fre-
quency. When connecting more than one microphone, the usage of sample rate converters for
clock-decoupling is unavoidable.
In the newer Mode 2 the digital microphone is clock slave. The DMC-842 determines the fre-
quency and generates a digital control signal for each microphone. A sample rate conversion is
not required in this case.
The microphone signals the supported mode, the DMC-842 switches its input accordingly. The
LED MODE 2 therefore is a state display only.
Note: Not every digital microphone supports Mode 2. With regard to the outstanding SRC built
into the DMC-842 Mode 1 can be seen as equally good alternative. However the SRCs delay
the audio signals by about 141 samples. At 44.1 kHz, this equals about 3 ms.
9.5 Stereo / Inactive
The DMC-842 has 8 single AES/EBU compatible inputs, being a 2-channel (stereo) input each.
At the time of printing this manual, digital stereo microphones not yet exist. A digital microphone
therefore provides only the information of one channel per input. For maximum flexibility the
operation mode can be switched between 2-channel and 1-channel. The labeling of the input
XLR connectors has been done to signal this flexibility. The odd ones are labeled Stereo (1/2),
the even ones Mono (2).
When an odd channel is switched into
STEREO mode, the according even channel’s INACTIVE
LED lights up automatically. The gain can not be set directly for inactive channels. Therefore in
Stereo mode the gain display of the right channel is turned off.
9.6 M/S Processing
The DMC-842 includes a digital M/S processor. The channels have a fixed assignment: all odd
ones are M, all even ones are S. The front panel shows an according labeling:
Channel 1 M/S (D)
Channel 2 M/S (D)
The mid/side principle is a special positioning technique for microphones, which results in a mid
signal on one channel and a side signal on the other channel. The DMC-842’s M/S processor
transforms these information back into a standard stereo signal. The process sends the monau-
ral mid channel to left and right, the side channel too, but phase inverted (180°) to the right
channel. For a better understanding: the mid channel represents the function L+R, while the
side channel represents L-R.
The M/S-Processing automatically operates as M/S encoder or decoder, depending on the
source signal format. When processing a usual stereo signal, all monaural information will be
shifted into the left channel, all stereo information into the right channel. Thus the stereo signal
is M/S encoded. This yields some interesting insights into the mono/stereo contents of modern
music productions. Additionally some very interesting methods of manipulating the stereo base
and generating stereo effects come up, as it is then very easy to process the side channel with
Low Cut, Expander, Compressor or Delay. The most basic application is to change the level of
the side channel: this allows to manipulate the stereo width from mono to stereo up to extended
in a stepless way.