Philips IS 5022 Mark II, Instruction Manual

Page: 20 / 42

4 CALIBRATION
4.1
STANDARD
CALIBRATION
The Sound Enhancer is factory calibrated for an analog input and output
signal
of 15
dBu
(unloaded).
This means that
when
a
digital input signal
of 0 dB full scale is applied, the balanced analog
outputs
will be 15 dBu.
Furthermore if an analog input signal of 15 dBu is applied, the digital out
‑
puts
will be 0 dB full scale. This ensures that the full 20 bit digital signal ‑
range of
the
AD converter is
used.
If it is required to adjust or to recalibrate the Sound Enhancer first the
output
m u s t
be calibrated then the input can be calibrated. Do
n o t
reverse this sequence. The Sound Enhancer can be calibrated for analog
input/output signals
between
9
and
15
dBu.
4.2
PREPARATION
FOR
CALIBRATION
1.
Switch the Sound
Enhancer
off if powered up.
2.
Make
sure the
pot.
meters on
the
front panel are fully turned anti ‑
clock wise,
that is: unity gain.
3. Remove cover, use appropriate TORX screwdriver.
4. Locate XLR
PCB
( r e f e r
to
figure
4.2).
A digital source is required for calibration of the outputs which can be a
CD-player, a
DCC
or DAT-player etc. It will be more convenient to use a
professional test system like the Audio Precision “System One”.
4.3.
CALIBRATION OF
THE
OUTPUT
Locate
the trimpotmeters
3108 and 3109
Select digital input then connect a digital source of 0 dBFs (1
kHz)
Connect
a suitable dB -
meter
to the
analog
balanced
outputs (L/R)
Adjust the trimpotmeters so that both
outputs
give the desired read ‑
ing. This is always between 9 and 15 dBu.