User manual RANE FDA 18

[. . . ] Once the input and outputs are satisfactorily connected, set the input gain as high as possible without causing the overload (OL) indicator to illuminate steadily with very high input levels. NEVER CONNECT ANYTHING EXCEPT AN APPROVED RANE POWER SUPPLY TO THE RED THING THAT LOOKS LIKE A TELEPHONE JACK ON THE REAR OF THE FDA 18. This is an AC input and requires special attention if you do not have a power supply EXACTLY like the one that was originally packed with your unit. See the full explanation of the power supply requirements elsewhere in this manual. SYSTEM CONNECTION When connecting the FDA 18 to other components in your system for the first time, LEAVE THE POWER SUPPLY FOR LAST. [. . . ] In the PRE position, the MASTER level control is bypassed for that respective output and only the input GAIN control and the individual OUTPUT level control has any affect. 5. In the out position, the input is scaled for microphone input levels. In the depressed position, the input stage is set for line-level input. 6. These concentric controls set each individual output level. The inner knobs are for odd numbered channels, and the outer knobs are for even numbered channels. 7. When this little yellow LED illuminates, the foregoing information applies. If darkness persists at this location -- ignore the above. Use these for either a microphone or a line level input to be distributed by the FDA 18. Connect a balanced source to the respective "+", "­" and GND pins (pins 2, 3 and 1 respectively). An unbalanced input should connect to "+" and GND only. When using an unbalanced input, you may leave "­" open, or short it to GND, doesn't matter. 2. Connect two-conductor shielded cable to "+" and "­". Normally the shield is tied only at the next unit's input. For unbalanced use, you must ground the "­" output, Failure to do so results in improper operation. 3. This switch (mounted on the side) provides the ability to separate chassis ground and signal ground. Normally, this switch should be in the LIFT position (pull toward the rear). In some circumstances it may be necessary to move it to the opposite position to eliminate stubborn hum and buzz problems. We realize a scientific explanation of this switch would be helpful, unfortunately science doesn't seem to have much to do with it. [. . . ] The unit is shipped with this switch in the "grounded" position, tying circuit ground to chassis ground. If after hooking up your system it exhibits excessive hum or buzzing, there is an incompatibility in the grounding configuration between units somewhere. Your mission, should you accept it, is to discover how your particular system wants to be grounded. Try combinations of lifting grounds on units that are supplied with ground lift switches or links. [. . . ]