Issue 2, December 2013
Model 42A User Guide
Page 10
Studio Technologies, Inc.
The Model 42A’s audio inputs have a
nominal signal level of +4 dBu. They are
transformer coupled, have an impedance
of 10 k ohms, and are compatible with
balanced or unbalanced sources. A bal-
anced source should be wired so that sig-
nal high is connected to the + pin, signal
low to the – pin, and shield to the shield
pin. With an unbalanced source, connect
signal high to the + pin, and shield to both
the – and the shield pins. If connecting an
unbalanced source in this manner results
in hum or noise, try connecting signal high
to the + pin, and shield to the – pin; leave
the shield pin unterminated.
As previously mentioned, the Model 42A is
compatible with matrix intercom systems
from Riedel. Appendix A, located near the
end of this user guide, provides detailed
connection information.
IFB Outputs
The Model 42A’s four independent IFB
outputs each supply DC power and two
channels of unbalanced audio. The IFB
outputs are designed to connect to a vari-
ety of devices that conform to the broad-
cast IFB standard. In this implementation
pin 1 is used for a combination of shield,
DC power return, and audio common;
pin 2 supplies a combination of DC power
and one channel of unbalanced audio;
pin 3 supplies a second channel of unbal-
anced audio. The DC power supplied on
pin 2 is 30 volts with a maximum current
of 220 milliamperes. The audio superim-
posed on the DC power has a nominal
signal level of –10 dBu. Its audio source
is the channel 1 audio input associated
with that specific IFB output. The audio
Signal
Signal
Connections
High (+)
Low (–) Shield
IFB Output 1-Channel 1
24
12
25
IFB Output 1-Channel 2
10
23
11
IFB Output 2-Channel 1
21
9
22
IFB Output 2-Channel 2
7
20
8
IFB Output 3-Channel 1
18
6
19
IFB Output 3-Channel 2
4
17
5
IFB Output 4-Channel 1
15
3
16
IFB Output 4-Channel 2
1
14
2
Notes:
1) Connector type on Model 42A is 25-pin D-subminiature
female. Installer must provide plug (male). Connector uses
4-40 threaded inserts for locking with mating plug.
2) Wiring scheme follows TASCAM DA-88 convention.
Standard DA-88-style wiring harnesses are directly
compatible, with the exception of 4-40 screw threads being
required.
Figure 4. Connections for audio inputs using
dual-channel nomenclature
Signal
Signal
Connections
High (+)
Low (–) Shield
IFB Output 1-Interrupt
24
12
25
IFB Output 1-Program
10
23
11
IFB Output 2-Interrupt
21
9
22
IFB Output 2-Program
7
20
8
IFB Output 3-Interrupt
18
6
19
IFB Output 3-Program
4
17
5
IFB Output 4-Interrupt
15
3
16
IFB Output 4-Program
1
14
2
Notes:
1) Connector type on Model 42A is 25-pin D-subminiature
female. Installer must provide plug (male). Connector uses
4-40 threaded inserts for locking with mating plug.
2) Wiring scheme follows TASCAM DA-88 convention.
Standard DA-88-style wiring harnesses are directly
compatible, with the exception of 4-40 screw threads being
required.
Figure 3. Connections for audio inputs using
IFB nomenclature
