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for 600 ohms secondary impedance . .
To re-
connect for 150 ohms refer to the schematic
diagram . . Remove the green/white and black
wires from terminal #7. Connect the black
w ire to terminal #5 and the green/white
\V
ire
to terminal #6.
EXTERNAL CONNECTIONS
External connections are made to the mount-
ing tray receptacle as follows:
Circuit
External Control (Optional)
+30 V.
Circuit Ground
Output Connections
Output Center"-Tap (600 ohms)
Input Connections
Input Center-Rap
-30 V.
Chasis Ground
No Connection
Terminals
1,2,3
4
4
5,6
7
9,10
11
12
13
8,14,15,16
Jumper together all #13 terminals on the
shelf, whether program amplifiers or other
types, and connect to the rack ground bus.
Connection from rack ground to the circuit
ground in the program amplifier (B+) should
be made at the amplifier (not at the power
supply).
Make a connection from the rack
ground bus to each amplifier terminal #14,
SEPARATELY, with at least 18 guage wire.
These circuit grounds must be carried sepa-
rately to prevent the possibility of interac-
3
tion (due to mixing of return currents in a
common wire). Where other types of amp-
lifiers are mounted on the same shelf, con-
sult their respective Instruction Book for
grounding information.
Where many ampli-
fiers and power supplies are mounted in a
rack, it is preferClble to run a vertical rack
ground bus-bar, to pick up grounds at each
shelL
Run the D . . C. supply leads, output pair,
and chassis and circuit ground leads along
the rear edge of the shelf. The D.C " " supply
leads shouldbe at least 18 gauge, and must
be run SEPARATELY from each program amp-
lif~erto
its respective power supply, to pre-
vent the possibility of common coupling in
the power wiring. See the power supply In-
struction Book for further information.
Run input pairs and external control leads
along the shelf brace, above the receptacles.
EXTERNAL VOLUME CONTROL
Reference to the schematic diagram will in-
dicate that the program amplifier is wired to
accommodate an external volume control.
This feature makes it possible to locate the
volume control on an adjacent rack panel,
or on a console control panel, when the amp-
lifier is mounted internally.
The internal
control, R30,
must be disconnected when
the amplifier is to be used in this way. The
(R30) control may be ordered as part number
5500218000.
THEORY OF OPERATION
For the purpose of explanation, the program
amplifier can be considered to be made up
of two parts: the preamplifier, and the high
level amplifier.
THE PREAMPLIFIER
The four stage preamplifier has a transform-
er coupled input and ell1itter follower out-
put, with direct coupling utilized between
01 and 02, and between Q3 and 04.
01
and 02 transistors are low noise types de-
signed for use in critical low noise uppli-
cations.
Biasing is accomplished by a combination
of voltage divider and emitter resistance, as
with R2, R3, and RS. This method of bias-
ing also insures a high degree of tempera-
ture stability. Signal degeneration is pro-
vided for 01 by R6, and for 03 by R17.
A
loop feedback network connects from 03,
thru R7 and CS, to 01..
The large amount of
feedback and degeneration obtained by these
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