User manual ROTEL RA-931

[. . . ] Do not open: There are no user serviceable parts inside. Refer any service work to qualified technical personnel only. Power sources: Connect the unit to mains power only of the type described in this user guide or marked on the rear panel. The power source must provide a good ground connection. [. . . ] Do not remove the metal cover; there are no user-serviceable parts inside. -- 6 RA-931 TCS Twin Compressor System CONTROLS & INDICATORS 1Power ­ Switches the unit's power on and off. 2Instrument Input and Level ­ The front ¼" jack is intended for instrument level signals and the level control applies from 0 to 30db of gain to the signal. When using the front instrument jack, the rear inputs on Channel 1 are disconnected. 3Compression Controls (Attack, Release, Threshold, Ratio) ­ These four controls control the amount of compression and its' transient settings. These are continuously active throughout all V3 settings (V3 optimizes ranges for selected application). 4Noise Reduction Controls (NR Thresh, Shelf, NR Active LED) ­ These two controls set the noise reduction characteristics. They are continuously active throughout all V3 settings. Users can look at the LED to determine if the current NR is an expander or a gate by viewing it's dimming characteristics. When the LED simply turns on and off the NR is a gate, when it slowly fades in and out it is an expander. As the NR Thresh is increased, the noise reduction will become more sensitive to the signals. Thus, more of the signal will be affected by the NR. From there the ratio control sets how aggressively the compressor holds signals above the threshold to the operating level. Typically a good starting ratio of 2:1 is suggested for vocal settings, 4:1 for instruments, and :1 for limiting or sustain. Settings with extremely high ratios are called limiters because they limit the signal to the operating level. The attack and release controls are intended for controlling how quickly the compressor begins (attack) and ends (release) its amplitude reduction. If your sound seems to lack punch try increasing the attack, and if too much of the peaks are coming through, decrease it. With release you want to increase the release time if you hear the compressor pumping, and you want to decrease it if it seems to lack sustain or dynamics. Expansion Basics ­ Expanders are basically the opposite of compressors such that they increase the dynamic range of a signal. Typically these are used to remove unwanted portions of a signal that are quieter than the working material. When there are gaps in the working material, the expander quiets signals beneath the noise reduction threshold to remove any unwanted sound and to increase lower level dynamics. An extreme variant of an expander is a gate, which mutes signals beneath the noise reduction threshold. Opto Basics ­ Optical compression is based on an optical ­ electric package made up of (in it's simplest definition) a light bulb and a photocell. [. . . ] Setting up the TCS as an instrument limiter Some instruments, particularly slap bass, can damage speakers or overload a mixer if recorded directly. Try running the bass into the instrument input, and select the VCA bass setting. This will clamp down on the spike and allow more overall gain without worrying about distortion or speaker damage. - 16 - RA-931 TCS Twin Compressor System Setting up the TCS for stereo mastering For bus mastering or stereo mix mastering try placing the TCS in the signal chain after the mixer, or on a subgroup bus. From there try the OPL settings labeled MIX and VOCAL. [. . . ]