User manual DBX 786

[. . . ] ¨ 786 Precision Mic Preamp Owner's Manual WARNING CAUTION RISK OF ELECTRIC SHOCK DO NOT OPEN FOR YOUR PROTECTION, PLEASE READ THE FOLLOWING: WATER AND MOISTURE: Appliance should not be used near water (e. g. near a bathtub, washbowl, kitchen sink, laundry tub, in a wet basement, or near a swimming pool, etc). Care should be taken so that objects do not fall and liquids are not spilled into the enclosure through openings. POWER SOURCES: The appliance should be connected to a power supply only of the type described in the operating instructions or as marked on the appliance. [. . . ] Detail Control This control adjusts the amount of boost or cut of the high frequency shelving EQ. "-" is typically better than -30dB. The cut and boost curves are symmetrical from 16dB boost to 16dB cut (ie: a 2dB boost produces a shelving curve that is the mirror image of the shelving curve produced by a 2dB cut). When the control is set to -, the band acts like a low pass filter whose slope is determined by the 12dB/OCT switch. 12dB/OCT Switch and LED Engage this switch (the adjacent LED will light) to set the slope of the shelving curve to 12dB/Octave. Leaving the switch in the "out" position sets the slope to a gentler 6dB/Octave rate. For example, a 12dB setting for the slope can let you create a sense of "air" without the stridency caused by too much boosting of upper mid range frequencies. Figure 4 on the next page shows the behavior of the 786's EQ section. HF EQ switch The hardwired EQ in/out switch bypasses the EQ circuit in the audio path. Settings on the Detail and Spectrum controls, as well as the 12dB/Octave switch are nullified by disengaging the HF EQ switch. 6 controls 786 dBr A B C D dBr Operating A B C D A: B: C: D: 16dB Cut @ 5kHz; 6dB/Octave Slope 16dB Cut @ 5kHz; 12dB/Octave Slope - Cut @ 5kHz; 6dB/Octave Slope - Cut @ 5kHz; 12dB/Octave Slope A: B: C: D: 16dB Boost @ 12kHz; 12dB/Octave Slope 16dB Boost @ 12kHz; 6dB/Octave Slope 16dB Cut @ 12kHz; 6dB/Octave Slope 16dB Cut @ 5kHz; 12dB/Octave Slope Figure 4: Audio Precision plots of the 786's EQ section. Peak LED The Peak LED is located to the left of the VU Meter. It is set to light when the signal level is within 3dB of hard clipping. The LED monitors three different points in the signal path: output of the Gain control stage, the output of the Fine control stage, and the output of the EQ stage. VU Meter The VU Meter is a custom dbx meter and monitors the output signal of the 786. +48V Phantom Power Switch and LED This switch activates phantom power for condenser microphones on pins 2 and 3 of the XLR mic input. Make sure to connect your microphone before activating the phantom power to prevent high voltage arching, which may damage your microphone. Super Low Z Input Switch and LED Typically microphones have an output impedance of 150. The 786 is set to operate in this range without any adjustments necessary. In some instances, a microphone may operate at a much lower impedance, like 20. (ie: some ribbon microphones) The Super Low Z switch optimizes the input circuit of the 786 for proper damping of these low impedance microphones, and to ensure that the input transformer is always fed by the same impedance for consistent performance. 20dB Pad Switch and LED This switch inserts a 20dB attenuator circuit into the signal path from the microphone input. The pad is inserted before the signal is routed through the mic pre gain stage. Use the 20dB pad to attenuate signals from hot sources such as high output microphones, or when the source is a line level device. [. . . ] 20 Hz to 20 kHz +0/-0. 1 dB 2 Hz to 200 kHz +0/-3. 0 dB Typically -128 dBu, 150 source impedance, unweighted, 20 Hz to 20 kHz measurement bandwidth. 0. 005% typical at +4 dBu out, 1kHz, 35 dB gain. 0. 0009% typical at +24 dBu out, 1kHz, 35 dB gain. Typically -105 dB, 20 Hz to 20 kHz. 11 Specifications 786 Sweepable from 5 kHz to 40 kHz. [. . . ]