StudioTech M46-00180 Wire Line Outputs, Detail of back panel showing line inputs and outputs

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 trans- mission system. The 4-wire input circuitry is balanced, capacitor coupled, transform- er isolated, and has an impedance of 13 k ohms. The line inputs are compatible with signals that have a nominal level of 0, +4, +6, or +8 dBu. Configuration switches, located on the Model 46’s front panel, al- low the circuitry to be adjusted to match the connected nominal level. The switches work in tandem to control both the input and output nominal levels.

Audio sources are connected to the line inputs by way of 3-pin female XLR-type connectors which are located on the unit’s back panel. Refer to Figure 1 for a detailed view. Note that pin 1 of these connectors is internally connected to the Model 46’s earth/chassis ground point.

Prepare the mating connectors (males) so that 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 remov- ing the shield connection from pin 1 can eliminate the issue; “floating” pin 1 will

remove a potential ground current path from the Model 46’s earth/chassis ground point through the shield of a cable. Also, if a hum or noise issue does arise be certain to confirm that, unless absolutely neces- sary, 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 connector is often the cause of seem- ingly inexplicable noise issues.

With an unbalanced source connect pin 2 to signal high (+ or hot) and both pins 1 and 3 to shield. If connecting an unbalanced source in this manner results in hum or noise, connect pin 2 to high (+ or hot) and pin 3 to shield; leave pin 1 unterminated.

4-Wire Line Outputs

Each of the Model 46’s two interfaces provides two analog line-level audio out- puts. These outputs are intended to be connected to inputs on the devices asso- ciated with the 4-wire audio signals. The outputs are capacitor coupled, transform- er balanced with a nominal level of 0, +4, +6, or +8 dBu. As previously mentioned, the 4-wire nominal level configuration switches, located on the Model 46’s front panel, control the level of both the line outputs and the line inputs. The 4-wire line