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1.4 The Modules of the Digital Controller
This is a brief description of the „modules“ provided inside the O 500 C. Please understand that
these modules are not meant to be physically independent, many of them are part of the integrated
DSP. To keep the description simple and understandable, it is restricted to the modules which are
important for understanding the internal functions in the signal path.
- Analog Input:
The input for the analog signals is balanced on studio-level ( + 6 dB ) and can be
selected between electronically balanced or transformer balanced by a switch next to the XLR.
- AD Converter:
in this stage of A/D conversion the „gain rangeing“ method was chosen to obtain
the max. possible dynamic in the input stage by using two A/D converters. The first A/D converter
is fed directly from the audio input signal and is set to produce a fixed level of gain, which is then
processed into the second converter. This way a much higher dynamic headroom and gain than
in any other A/D design is obtained.
- Digital Input:
The O 500 C has digital inputs following the AES/EBU format, connected to a
transformer-balanced XLR socket, and a S-PDIF format connecting to a BNC socket.
- Input Select:
The selection of the input-type is made via the remote control in the main menu,
step INPUT SELECT, here shown as a selector switch.
- Digital Output:
The digital output of the O 500 C is in the AES/EBU format connected to an XLR
socket. Factory preset is parallel „input to output“, i.e. a direct link to the output, so the signal can
be fed to the next O 500 C in a stereo setup. In the menu DIGITAL INPUT SELECT you now may
choose the L or R channel from the digital data stream.
.
- EQ Gain:
at this stage the digital signal can be reduced or raised by an adjustment of the word
length to match the peaks or dips in the following parametric EQ. The level selected at this point
also remains valid, if the PEQ is in EQ OFF. This way it is possible to make A/B comparisons
without level mismatch.
- 10-Band parametric IIR EQ:
the parametric EQ ( PEQ ) of the O 500 C is designed as an IIR
digital filter and contains 10 fully parametric bands with selectable characteristics. By using
these filters it is possible to obtain a system-EQ separately for the LEFT and RIGHT channel.
The full adjustment procedure of the EQ’s is explained in chapter 5.2
- Room IIR EQ:
this room EQ is designed to be an IIR filter, just like the PEQ filters. It is designed
for simple compensation of typical room influences and unlinearities. The adjustment is made in
the EQ setting of the EQ menu, as described in chapter 5.1.
- Master Delay:
The master delay is the final stage in the signal path, before the signal is devided
by the 4-way electronic crossover. Adjustment is made in the menu „MASTER DELAY“, the
delaytime selected is effecting all four signals. It can be adjusted in meters or seconds.
In the crossover section there are four identical modules from which the user may select the
wanted parameters. As these paths are almost identical, ( the MID, LOW and SUB have additional
downsampling filters to compensate for calculation-speed ) the HIGH signal to describe the functions
is chosen here.
- High (Mid, Low, Sub) Delay:
every signal in the 4-way crossover can be delayed individually.
This can be done in the MAIN menu
Channel Delay
.
- High (Mid, Low, Sub) X-Over + Speaker EQ:
Here the bandpass filters were chosen to be FIR
digital filters for every driver. Please note that this feature does not only offer an EQ for the
