DMM
6
43
Description
Analogue control
Figure 11: Phoenix terminal
A linear 50 kOhm potentiometer at the VCA input,
labelled "VCA" and "
A
", allows you to vary
the master volume.
Figure 12: VCA
The linear potentiometer is connected to the VCA input as shown above. The resistance at the
VCA input is changed by turning the potentiometer. This value is input and the volume is
changed accordingly. The left setting signifies 0% while the right setting signifies 100%.
The output level depends on the master control and the remote level control. The remote level
control has the same affect on both masters.
Power switch
The power switch is used to turn on the unit.
The unit's automix algorithm has 3 basic functions which assess the amount by which an
input signal is to be attenuated and the output signal's output level. The following functions
and parameters flow into the automix algorithm:
Dynamic level adjustment
The master of all input channels is determined on an ongoing basis. This value is used as the
reference value. If the input channel level is very close or over the reference value, this
channel will be assessed as dominant and will be slightly attenuated. If the input channel level
is well below the reference value, this is assessed as ambient noise and be severely
attenuated.
A channel's output level is calculated using the following formula:
Output level = Input level - (Reference value - Input level)
This formula ensures that the output level will not become louder if several input channels are
active, rather the master assumes the level of a single channel. This reduces the risk of
feedback.
If a channel is no longer assessed as dominant, this falls at 1 dB/second and all other non-
dominant channels increase with the same constant so that the master output level remains
constant. The upward adjustment of a channel takes between 3
ms and 5
ms.
Best Mic On
With two microphones that are positioned close together there is the disadvantage that comb
filter effects may arise by cancelling the frequency components. To suppress these unnaturally
muffled or hollow signals, only the microphone channel with the highest level is assessed as
dominant and switched on.
Noise Detect
Permanently present interfering signals, whose amplitude are large enough to be assessed as
dominant, but whose level and frequency changes are too low, are not assessed as dominant.
Interfering signals such as noise from fans and air-conditioning units are recognised and not
used as activation criteria for microphone channels.
Automix algorithm
