StudioTech M45-00151 manual Wire Audio Inputs and Outputs, Wire Line Inputs

Once the desired one or two Model 45 units have been installed in a rack-mount front panel, the assembly can be mounted into the designated equipment rack. One space (“1U” or 1.75 vertical inches) in

a standard 19-inch equipment rack is required. Secure the unit into the equip- ment rack using two mounting screws per side.

4-Wire Audio Inputs and Outputs

Two audio line input and two audio line output signals are associated with the

4-wire interface section of the Model 45. Connections are made using standard

3-pin male and female XLR connectors. Refer to Appendices A, B, and C for de- tails on interconnecting with RTS, Riedel, and Clear-Com matrix intercom systems.

4-Wire Line Inputs

As previously mentioned, the Model 45’s 4-wire interface allows two analog line- level audio sources to be connected. The source for these signals will typically be ports on a matrix intercom system. It’s also possible that the signals will come from other devices, such as a fiber optic or copper-based audio transmission sys- tem. The 4-wire input circuitry is balanced, capacitor coupled, transformer isolated,

and has an impedance of 13 k ohms. The line inputs are optimized for signals that have a nominal level of +4 dBu.

Audio sources are connected to the line inputs by way of 3-pin female XLR-type connectors which are located on the Model 45’s back panel. Refer to Figure 4 for a detailed view.

Prepare the mating connectors (males) so that XLR pin 2 is signal high (+ or hot), pin 3 is low (– or cold), and pin 1 is shield. If connecting a source in this manner results in hum or noise it’s possible that removing the shield connection from

pin 1 can eliminate the issue; “floating” pin 1 will remove a ground current path from the Model 45’s chassis ground point through the shield of a cable. (Pin 1 on each of the two input connectors is inter- nally connected to the Model 45’s earth/ chassis ground point.) Also, if a hum or noise issue does arise be certain to con- firm that, unless absolutely necessary, the mating connector’s “shell” isn’t connected to the cables’ shield or pin 1. Termination of this “fourth” pin of a 3-pin XLR connec- tor is often the cause of seemingly inexpli- cable noise issues.

With an unbalanced source connect XLR pin 2 to signal high (+ or hot) and both pins 1 and 3 to shield. If connecting an

Figure 4. Detail of back panel showing line inputs and outputs

Issue Preliminary 2, March 2009	Model 45 User Guide
Page 12	Studio Technologies, Inc.