User manual RANE FPL 44

[. . . ] In this position all channels in AUTO-SLAVE limit by the same amount when any one channel exceeds its threshold level. set at different thresholds to suit the requirements of each situation. If one channel is overdriven by, say, 10 dB, its gain and the gain of all others in the slave mode reduces by the same 10 dB. NEVER CONNECT A NYTHING EXCEPT AN APPROVED RANE AC POWER SUPPLY TO THE THING THAT LOOKS LIKE A RED TELEPHONE JACK ON THE REAR OF THE FPL 44. [. . . ] It doesn't really make a lot of sense to beat this issue to death alter having done so twice on the first page. REAR PANEL DESCRIPTION 1. One of four, this connector provides either a balanced output on pins 2 and 3 or an unbalanced output between pins 2 and 1. Pin 2 is positive, pin 3 is negative and pin 1 is signal ground. 2. Each of the four channels of the FPL 44 makes use of one of these to supply either a balanced or unbalanced input to the limiter circuitry within. For balanced operation, the positive signal is applied to the tip, the ring receives the negative and the sleeve is to be used for signal ground connection. Unbalanced input may be applied to each channel by driving the tip and using both ring and sleeve for signal ground or the sleeve alone. The simplest unbalanced input connection is realized by using a tip-sleeve (often referred to as a mono) plug which eliminates the need for ring worry. 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. See the CHASSIS GROUNDING note on the last page for details. CAUTION: If you are tempted to try moving this switch with your power amplifiers turned on or turned up, DON'T BE. ALWAYS TURN YOUR AMPLIFIER LEVELS DOWN BEFORE CHANGING YOUR GROUNDS AROUND and then bring them up slowly. 4. This is the spot where the "appropriate power supply" connects. Again, for a complete definition of the power supply, look across to the facing page for information concerning the location nearest you. 5. Since the FPL 44 is powered from a remote AC power supply which does not carry chassis ground through to the grounding pin of the AC cord, this threaded hole has been provided in case your system does not have another earth grounding means such as through rack rails, etc. Its use or disuse should be determined by your specific application. OPERATING INSTRUCTIONS To give you a better understanding about the operation of the FPL 44, a quick course in its design should be useful. Included as a part of this manual is the data sheet covering this product. This sheet includes a block diagram of one channel of the unit. You may want to consult this document to aid you in understanding the following. The limiter circuit used in this module is what Rane refers to as a "servo-locked limiter. ""' This term derives from the similarity of this design to that of a servo motor such as is used in robotics and precision control systems. [. . . ] CHASSIS GROUNDING Rane Flex Series modules are supplied with either a rear, or a bottom/side mounted ground-lift switch. 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, I 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. [. . . ]