Studio Technologies Model 47A Dual 2-Wire Analog Audio to 4-Wire Analog Audio Interface

The Model 47A is designed to interface 2-wire full-duplex party-line (PL) intercom circuits with 4-wire audio circuits associated with matrix intercom systems. Other specialized audio system interfacing applications can also be supported. The Model 47A provides two independent full-featured 2-channel interfaces. Each interface contains two hybrid circuits which include automatic nulling capability. The analog circuitry, under software control, provides excellent audio quality and high return-loss. The interfaces are compatible with powered and unpowered 2-wire party-line circuits. They are capable of supplying DC power to devices such as user beltpacks and user stations. Independent power sources are provided for both channels (pins 2 and 3) of each interface, allowing direct support for broadcast source assignment panel (SAP) applications. Configuration settings allow the 2-wire and 4-wire interface circuitry to be compatible with a range of nominal signal levels. Audio level meters provide user confirmation of system performance during setup and operation. Applications for the Model 47A include mobile and fixed television facilities, theme park and theater installations, and industrial testing environments. Standard audio connectors are used for all input and output signals. The Model 47A mounts in one space (1U) of a standard 19-inch rack enclosure and requires 100-240 V, 50/60 Hz for operation.

Key Features

• Two 2-channel party-line intercom interfaces
• Four analog hybrids with auto null capability
• Input and output level metering
• Excellent audio quality
• 2-channel intercom power sources
• Direct support for broadcast SAP panel applications
• Standard audio connectors
• Universal input mains powered

Technical Specifications

General Audio
Frequency Response
+/-2 dB 100 Hz to 8 kHz
Distortion (THD+N)
<0.5%, measured at 1 kHz, 4-wire input to 2-wire interface pin 2
Signal-to-Noise Ratio
>55 dB, measured at 1 kHz, 4-wire input to 2-wire interface pin 2
Connectors
Inputs from 4-Wire
3-pin female XLR
Outputs to 4-Wire
3-pin male XLR
2-Wire Party-Line Intercom
3-pin male XLR
Remote Control
10-pin header, requires user-provided 10-pin ribbon connector assembly
AC Mains
3-blade, IEC 320 C14 (mates with IEC 320 C13)
2-Wire Party-Line Intercom Interfaces
2
Type
2-channel party-line (PL), unbalanced (pin 1 common; pin 2 channel 1 audio or DC with channel 1 audio; pin 3 channel 2 audio or DC with channel 2 audio)
Compatibility
single- and 2-channel intercom systems such as from RTS and Clear-Com Impedance, External Power Mode
>10 k ohms Impedance, Internal Power Mode
200 ohms
Nominal Level
-10 or -14 dBu, selectable
“Mic Kill” Signal
square wave, 24 kHz, +/-1%
2-Wire Party-Line Power Sources
4, 2 per interface
Rating
30 volts DC nominal, 315 mA maximum, software monitored and controlled
Hybrids
4, 2 per interface
Topology
3-section analog circuitry compensates for resistive,
inductive, and capacitive 2-wire party-line loads
Nulling Method
automatic upon user initiation, processor implements digital control of analog circuitry; null settings stored in non-volatile memory
Nulling Line Impedance Range
120-350 ohms
Nulling Cable Length Range
0-3500 feet, typical
Trans-Hybrid Loss
>40 dB, typical at 800 Hz
4-Wire Inputs
4, 2 per interface
Type
transformer-coupled, capacitor isolated
Impedance
13 k ohms
Nominal Level
0, +4, +6, or +8 dBu, selectable in tandem with nominal output level
Maximum Level
+22 dBu
4-Wire Outputs
4, 2 per interface
Type
transformer-coupled, capacitor isolated
Impedance
50 ohms nominal
Nominal Level
0, +4, +6, or +8 dBu, selectable in tandem with nominal input level
Maximum Level
+20 dBu into 2 k ohms
Meters
8
Function
displays level of 4-wire inputs and outputs
Type
5-segment LED, modified VU ballistics
Remote Control Inputs
3
Type
optically coupled
Input
3-32 volts DC; 2 mA minimum for operation, 20 mA maximum
Functions
auto null interface 1, auto null interface 2, and “mic kill”
AC Mains Requirement
100-240 volts (-15/+10%), 50/60 Hz,
60 watts maximum
Dimensions (Overall)
19.0 inches wide (48.3 cm)
1.72 inches high (4.4 cm)
8.4 inches deep (21.3 cm)
Mounting
one space (1U) in a standard 19-inch rack
Weight
4.7 pounds (2.1 kg)