Studio Technologies 58 2000 - Manual (Page 22)

Model 58/59 User Guide Issue 4, December 2000
Studio Technologies, Inc. Page 23
for Surround
Level Calibration
Fourteen multi-turn trim potentiometers
grace the front panel of the Model 58
Central Controller. Eight are provided
for the main inputs, four for the insert
returns, and two for the monitor outputs.
Taking time to carefully adjust the trim
pots will ensure that accurate monitoring
can take place. Each trim pot allows an
adjustment range of ±2dB, which is spread
over the trim pot’s 15 turns. Calibrating
the levels down to a tenth of a dB is easily
performed.
The meter outputs are used as the mea-
suring point when adjusting 12 of the 14
trim pots. Unless calibrated level meters
are already connected to the meter out-
puts, an external audio level meter is
required. In addition, the audio sources
connected to the main inputs must be
configured to generate steady signals at
nominal operating level. Those interested
in where the trim pots are located in the
circuitry, and why the meter outputs are
specified as a measurement point, should
refer to the Model 58 Block Diagram,
located at the end of this guide.
Main Input Trim Pots
This first procedure will ensure that all
Model 58 main inputs are level matched
against each other. The audio sources
connected to these inputs are normally
arranged as four 2-channel pairs; 1 and 2,
3 and 4, 5 and 6, 7 and 8. The trim pots
will be adjusted in pairs corresponding to
the input sources. In this procedure it is
assumed that calibrated metering devices
are not already connected to the meter
outputs.
1. On the first Model 58, connect the
audio level meter to meter output 1.
2. Using the Model 59 Control console,
select input 1 as the audio source.
Be certain that inserts 1 and 2 are not
enabled. Enable the mute all function,
ensuring that you won’t have to hear
a steady tone during the entire
procedure!
3. Confirm that the audio source con-
nected to main inputs 1 and 2 is gen-
erating a steady signal at precisely its
reference level. (This is assumed to be
nominally +4dBu.)
4. Observing the level meter, adjust main
input trim pot 1 to give a +4dBu level
at meter output 1.
5. Disconnect the level meter from meter
output 1 and reconnect it to meter
output 2.
6. Observing the level meter, adjust main
input trim pot 2 to give +4dBu.
7. Repeat steps 1-6 for inputs 2, 3, and 4.
This will calibrate main inputs 3-8.
Once all eight main inputs on the first
Model 58 have been calibrated, repeat the
entire procedure for the additional Model
58 units.
Insert Return Trim Pots
Describing the calibration process for the
insert returns is a bit more difficult as the
exact implementation of the insert sections
is dependent upon the specific installation.
The goal is to have no unwanted level
change occur when switching an insert
section between disabled and enabled.
Note that the insert sends are not cali-
brated for a precise +4dBu nominal level.
Trim pots on the insert returns allow level
inaccuracies in the insert sends, as well as
the connected device’s input and outputs,
to be accounted for.