Parameter Notes; Faders; Faders With User Min And User Max Limits - Symetrix Composer v7.0 Manual

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Parameter Notes

Faders

Faders can be controlled to the limits of their minimum
and maximum values shown in the Design View screens in
Composer. A controller position of zero (0) will cause the
minimum fader position to be realized. A controller position
of 65535 will cause the maximum fader position to be
realized. Increasing positions will move the fader linearly in
dB.
Most volume faders have a range of -72dB to +12dB. In
these cases, the following formula can be used to convert
from controller position to dB:
Volume dB = -72 + 84*(CONTROLLER POSITION/65535)
If CONTROLLER POSITION = 0, Volume dB = OFF
For these faders, a value of 780 is approximately equal to a
1dB change in gain.
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Note that some faders have a different range than –72 to
+12dB. In this case, the formula will depend upon the actual
fader range. The more general formula is shown below:
Volume dB = MINIMUM VALUE + (MAXIMUM VALUE – MINIMUM
VALUE)*(CONTROLLER POSITION/65535)
Where MINIMUM VALUE is the fader's lower limit in dB and
MAXIMUM VALUE is the fader's upper limit in dB.

Faders with User Min and User Max Limits

There are some applications where it is desired to limit the
range of adjustments for an end user, perhaps to allow a
more useable range of adjustment than the full range of the
fader or to prevent the system from getting too loud. To
limit the gain range of a fader to a user minimum and user
maximum range, the following formulae may be used.
In the following discussion, it is assumed that the range of
the variables (in dB) are as follows:
MAXIMUM VALUE ≥ User Maximum ≥ User Volume ≥ User
Minimum ≥ MINIMUM VALUE
The controller position is calculated the same as described
previously:
To determine the controller position based on a desired
User Volume in dB, then the controller value is calculated as
follows:
Controller Position = (User Volume in dB – MINIMUM VALUE) *
65535 / (MAXIMUM VALUE – MINIMUM VALUE )
The percentage value of the fader control relative to the User
Min and User Max values is computed as:
Volume Percent = (User Volume in dB – User Min) / (User Max –
The controller position required to set the fader to a
percentage of the user min and user max may be computed
as follows:
Controller Position = (Volume Percent * (User Max – User Min)
+ (User Min – MINIMUM VALUE)) * 65535 / (MAXIMUM VALUE –
For example, if the Maximum and Minimum Values are +12
and -72, respectively, and the desired User Max and User
Min are +6 and -30 respectively, then the controller value for
setting the fader to -8dB is:
Controller Position = ((-8) – (-72))* 65535 / ((+12) – (-72)) =
49931
The controller position corresponding to 35% volume with
the same User Max and User Min range would be:
Controller Position = (35% * ((+6) - (-30)) + ((-30) - (-72))) *
65535 / ((+12) - (-72)) = 42598
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Parameter Notes
User Min)
MINIMUM VALUE)