Studio Technologies AN-2 - Manual (Page 8)

Issue 3 AN-2 User Guide
Page 10 Studio Technologies, Inc.
Broadcast and Film Applications
Television stations that are in the process
of converting to stereo can use the AN-2 to
process mono program material to stereo,
allowing full-time stereo programming. For
program material of a general nature con-
taining speech and music, the stereo depth
control is best set about mid-range and the
stereo width control about three o’clock.
Programs consisting primarily of music can
benefit from more opening of the controls,
while programs that are mainly speech
should be processed with the controls less
open. The modulation control should not be
used for “on air” broadcasting. Leaving the
modulation ON/OFF switch in the OFF
position disables the modulation section;
if you want to be absolutely certain that the
modulation section will not be accidently
turned on, remove U15 (see schematic)
after disconnecting power to the unit.
AM and FM stereo radio stations will find
use for the AN-2 in converting old records
to stereo or “fattening” D.J. and announcer
voices. Again, careful use of the stereo
depth and width controls can result in opti-
mum sound. Also, many commercials are
received by the station in mono and can be
enhanced by conversion to stereo.
The AN-2 can be employed in film studios
to remix mono movie sound tracks to ste-
reo. Older music and sound effects libraries
can also be upgraded.
Theory of Operation and
Troubleshooting
The following paragraphs describe the
theory of operation of the AN-2. This infor-
mation will help you understand where a
failure may be located. Please read this
material before attempting to troubleshoot
the unit.
Theory of Operation
Refer to the schematic diagram of the AN-2
while reading this material.
U9 is a balanced input amplifier with a trim
potentiometer to obtain maximum common
mode rejection. Two sections of the DIP
switch, SW1, are used to select –10 or
+4dBm operation.
P5 is the input gain control, which is fol-
lowed by a buffer amp. This amp sends a
portion of the input signal to U5, where the
two comb filters are produced by phase
addition and subtraction performed on the
delayed signal.
A pre-emphasis network precedes U11,
which acts as a compressor in a compandor
circuit. The compressor attack time is
speeded up by a charge pump U14, which
reduces transient distortion that is often
associated with compandors.
A 6-pole, 20kHz Butterworth filter removes
the possibility of audio frequencies aliasing
with the clock frequency from U1.
U6 acts as a bucket brigade delay line. The
line is driven by U2 and VCO U1, whose
frequency is set by the stereo width control,
P1.