15
Operating Manual-4048A digital signal processor
Attack and Release settings adjust the time it takes the limiter to engage and then disengage when the signal
increases above threshold and then subsequently falls back below threshold. Attack time is adjustable from 0.5ms/dB
through 50ms/dB, while release time ranges from 10ms/dB through 1s/dB. A very fast attack time can sound unnatu-
ral, while a very long attack time can miss some of the initial transient. Similarly, a very short release time can make
the audio sound uneven, while a very long release time can create "pumping", or "breathing" characteristics depending
on the kind of signal. Experiment to find the best solution for a given application.
Limiter linking is used to group the compressor/limiter action of multiple output channels. Selecting <Link>
within the output limiter section ties that channel to the "link bus", which in turn applies the same degree and charac-
teristics of gain reduction to all channels assigned to the link bus. The linked channel with the highest signal level
above threshold determines the gain reduction on the other linked channels. A prime example involves stereo signals.
Using limiter linking, the limiter action on both channels will track perfectly based on the loudest signal on either
channel, eliminating a level mismatch in the stereo image.
8. OTHER SOFTWARE FUNCTIONS
8.1 Channel Preset File Management
As discussed in section 7.2, there are 10 standard configurations which can be modified to create user defined
preset files. These modified presets can then be saved to either disk or the 4048 itself. For disk files, the file extension
is <*.alp>. For files saved to the 4048A, they must number from 1 to 18 and the filename must be no more than 20
characters. The 18 preset locations on the 4048A are initially filled with the same 10 standard configurations, repeat-
ing two times.
A preset file contains the control parameters of all four inputs and eight outputs. For a written record of all
parameters of a specific preset file, click <Print Channel> in the File menu.
Since there are no user controls on the 4048A, the only way to load channel presets is by using Altec Lansing
Software to recall files saved on either the PC or the 4048A. The exception to this is through the use of contact
closures, where presets 1-8 from the 4048A memory can be loaded using switches wired to the rear panel contact
closure connector block (see section 5.4).
Note: A preset recall event will overwrite any changes to the working channel, so be sure the current configu-
ration is saved before continuing or it will be lost. The 4048A always loads the last working channel on power-up, so
as to preserve any changes should the power be inadvertently turned off prior to saving a channel.
Caution: A new preset may have dramatically different settings capable of damaging sound system compo-
nents, so be careful not to recall the wrong preset while the system is on. To be safe, always select "Yes" to mute all
outputs.
8.2 RS-232 Bulk Preset Dump
To capture the entire set of 18 presets stored within a specific 4048A's memory, a <*.dmp> file is created by
clicking <Trigger Bulk Preset Dump> within the file menu. This file can then be written back to the same or another
4048A using <Download Bulk Preset Dump>. When a Bulk Preset Dump download to a 4048A is complete, the
display shows a lower case "d" to confirm the event.
8.3 Copying Settings to Another Input Or Output
The <Copy/Paste> functions are used to quickly transfer all settings from one currently selected input or
output within the 4048A to another input or output channel within the same unit. An example of how this might be
used is with stage monitors. Suppose there are eight monitor mixes on stage, and they all use the same type of floor
wedge. The first monitor could be set up with Gain, EQ, and Limiting, then those settings could be quickly copied to
