Studio Technologies AN-2 - Manual (Page 9)

AN-2 User Guide Issue 3
Studio Technologies, Inc. Page 11
U15 is an LFO which modulates the VCO
via P2 (modulation depth control) and P3
(modulation rate control).
A 5-pole, 20kHz low-pass Butterworth filter
removes clock frequency from the output
signal.
The expander, U11, restores the dynamic
range, using another charge pump, U3, in
the expander rectifier.
A proprietary randomizing circuit, labeled
N1, assures that the peaks and dips in the
combs do not fall on harmonics, preserving
the natural sound of the music.
U17 comprises the peak-reading meter
circuit; it combines a rectifier and three LED
drivers.
U5 is a mixer, interleaving the combs on the
left and right outputs. If P4, the stereo depth
control, is set fully counterclockwise, any
delay signal is removed, leaving only the
direct signal. This will also happen if the two
outputs are summed externally, since the
delay signal will be cancelled. The switches
following this IC set the output levels.
The two output stages, U7 and U8, are
differential balanced line outputs with cross
coupled output sensing feedback. This
circuit gives an additional 6dB of headroom
for a given supply voltage, while maintaining
the output level and keeping the opamp
current draw at a safe level, even if one side
of the output is shorted.
The power supply is bipolar, using two IC
voltage regulators to provide low ripple
±15Vdc. Two additional decoupling stages
provide isolation for the clock circuitry.
Equipment Needed for
Troubleshooting
The AN-2 is constructed of high-quality
solid state components. Given normal use,
there is no need for regular preventive
maintenance.
If repair does become necessary, you may
either have a qualified technician service
the unit or return it to the factory. Contact
the factory for a return authorization number
should you wish factory repair. When re-
turning your unit, be sure to pack it securely
and insure it for its replacement value.
If you decide to have a technician service
the unit, the following test equipment is
required to allow accurate troubleshooting
a component replacement:
• high-quality oscilloscope equipped with
balanced vertical and horizontal inputs
• low-distortion oscillator (.01%)
• harmonic distortion analyzer
• AC voltmeter with –80dBm sensitivity
• high-quality digital voltmeter
• adjustable attenuator box
• tone burst generator
• frequency counter
Troubleshooting and Alignment
WARNING: The following procedures must
be performed by a qualified technician.
Operating the AN-2 with the top and/or
bottom cover removed exposes the techni-
cian to points in the power input section with
hazardous voltages. USE CAUTION!