Studio Technologies Gen II - Manual (Page 9)

Generation II User Guide Issue 3, July 1991
Studio Technologies, Inc. Page 11
within 2dB of one of the Generation II’s
preset levels, set the input and output
switches to the closest value. If you are
exactly in between two of the choices, go
for the lower one. An example would be a
facility running +6dBu. Set the input and
output levels for +4. If you are running an
operating level below
–
2dB or above +10dB,
contact Studio Technologies for details on
simple operating level modifications.
Proof of Performance Testing
Proof of performance tests on a broadcast
facility commonly use sine waves of differ-
ent frequencies and levels to check such
things as frequency response, noise, and
distortion. Very unusual results can occur if
Generation II performance tests are made
using sine wave or constant frequency
signals. These results are due to the way
the unit creates simulated stereo, taking a
mono input and delaying, randomizing, and
gyrating the signal into a good stereo im-
age. Simulating stereo from a fixed fre-
quency input will result in different left and
right output levels that will appear to change
randomly as the input frequency is varied
slightly. This is completely normal and
expected. Remember that the usual input
signal is complex music, voice or other
natural sound.
To get rational proof of performance data,
either take the unit out of the signal path, or
reduce the stereo depth control to the
minimum, fully counterclockwise position. If
you wish to check The Generation II with
stereo simulation taking place, you need to
use pink noise. The randomness of pink
noise will allow left versus right frequency
response observation.
Circuit Description
In this section, we will review the Genera-
tion II’s circuitry. This information will assist
you in understanding the operation of the
unit, as well as providing a guide to trouble-
shooting any problems that may arise.
Operational amplifier sections of an inte-
grated circuit will be referred to as an “op
amp section,” or as an “op amp.”
Power Supply
A step down transformer converts the
incoming line voltage to nominal 40Vac.
The primary of the transformer is tapped for
either 115Vac or 230Vac input. A switch on
the back panel selects which tap is con-
nected. A fuse in series with the primary
protects the unit in case of a component
malfunction. The Generation II contains no
power switch. The power line is connected
directly, via the fuse, to the transformer.
This prevents the unit from being accidently
turned off. The secondary of the trans-
former has a center tap, which acts as the
circuit common, as well as being strapped
to the metal chassis and line cord ground
wire. The secondary of the transformer
connects to a full wave bridge rectifier. The
full wave bridge produces nominal ±30Vdc.
From the unregulated ±30Vdc two fixed
voltage 3-terminal regulators produce
±15Vdc. A resistor and zener diode combi-
nation produces
–
22Vdc. The audio circuitry
uses ±15Vdc, and the delay line oscillator
FET switch uses
–
22Vdc. An LED indicator,
in series with a resistor, is connected to
+15Vdc to provide an indication that the unit
has incoming power.