¨ 786 Precision Mic Preamp Owner’s Manual
WARNING CAUTION FOR YOUR PROTECTION, PLEASE READ THE FOLLOWING: RISK OF ELECTRIC SHOCK DO NOT OPEN A T T E N T I O N : RISQUE DE CHOC ELECTRIQUE - NE PAS OUVRIR W A R N I N G : TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE The symbols shown above are internationally accepted symbols that warn of potential hazards with electrical products.
contents 786 Manual Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 About Mic Preamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 Understanding Console Signal Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 Connection To Your System Operating Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction 786 Introduction About mic preamps When you use a microphone to record vocals and acoustic instruments, make recordings to DAT, or sample acoustic sounds, you want the best definition and character possible from your microphone. Sometimes the electronics of recording or PA consoles “color” the sound of a microphone, or add noise to the signal. In the 1960s, it became popular to use an outboard mic preamp rather than using the one usually installed on a console.
786 Introduction Understanding Console Signal Path Recording and PA consoles operate at a nominal level of +4dBu, while microphones operate at a level of typically about -50dBu. Microphone signals must be amplified to the appropriate level for a console to process it properly. If a signal is not raised to the appropriate level, the signal will be “masked” by the console’s internal noise, especially when one tries to increase the level of a low signal using the console fader or gain knob.
Connection to your system 786 The 786 is the perfect partner for your microphone, providing you with two channels of audio purist quality preamplification. The 786 delivers up to 70dB of sonically transparent gain to reveal the detail and audio signature of even the most esoteric studio mics.
to your system 786 Connection 2. Using the 786 to connect a mic directly to a recorder. 1. Make microphone connections as shown on the previous page, being careful to start with the Gain control in the +15dB position. 2. Connect the 786’s audio outputs directly to the audio inputs of your recorder (see figure 3). This will require the disconnection of the console’s audio output to the specific track of the recorder. 4.
controls Operating 786 Operating Controls Front Panel +40 +35 +40 +45 +30 +35 20 10 +50 -30 +25 +55 +20 +60 +15 +65 7 5 3 0 -15 -10 -25 -20 -5 DECIBELS ¨ 3 +45 +30 20 10 +50 + -30 0 +25 +55 +20 7 5 3 0 -15 -10 -25 -20 -5 DECIBELS 3 + 0 ¨ +60 +15 +65 Gain Control Use the Gain control to adjust the output level of the 786. Note that the Gain control is used as a “coarse” adjustment, ranging from +15dB to +65dB of gain, in 5dB increments.
controls 786 Operating A B dBr dBr A B C C D 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.
Operating controls 786 Rear Panel MANUFACTURED UNDER THE FOLLOWING U.S. PATENTS: 4,368,425 5,282,252. OTHER PATENTS PENDING. Au dio Input and Output Connectors Each audio input connector on the rear panel of the 786 is a gold-plated Neutrik® XLR female connector. The no-compromise approach to the 786 required that we use gold-plated connectors, due to their high conductivity and resistance to corrosion.
controls Operating 786 BALANCED FLOATING OPERATION UNBALANCED FLOATING OPERATION + + Chassis Ground 1 3 Jensen¨ Output Transformer Chassis Ground 2 1 2 3 Jensen¨ Output Transformer 10k 1W Ground Switch open Unbalance Switch open GND Switch Ground Switch open Unbalanced Switch closed GND Switch (6dB drop in output level) Chassis Ground Chassis Ground BALANCED GROUNDREFERENCED OPERATION UNBALANCED GROUNDREFERENCED OPERATION + + Chassis Ground 1 3 Jensen¨ Output Transformer 10k 1W GND
Technical support and factory service 786 sive damage which is not covered by the warranty. Output Option Panel This panel is removed when an output option card is installed in your 786. Connecting a custom designed digital output module in the option port provides full 24-bit AES/EBU and S/PDIF output capabilities for the 786.
786 Specifications Warranty This warranty is valid only for the original purchaser and only in the United States. 1. The warranty registration card that accompanies this product must be mailed within 30 days after purchase date to validate this warranty. Proof-of-purchase is considered to be the burden of the consumer. 2. dbx warrants this product, when bought and used solely within the U.S., to be free from defects in materials and workmanship under normal use and service. 3.
Specifications EQUALIZER Shelving Frequency: Gain: Slope: FUNCTION SWITCHES HF EQ: 12 dB/OCT: +48V: Super Low Z: 20 dB Pad: Ø Invert: Unbal (Rear Panel) Ground (Rear Panel) INDICATORS HF EQ: 12 dB/OCT: Peak: 786 Sweepable from 5 kHz to 40 kHz. Sweepable from -∞ to +16 dB. Selectable; 6 dB/octave or 12 dB/octave. Enables high frequency shelving equalizer. Changes equalizer slope from 6 dB/octave to 12 dB/octave. Sends regulated +48 VDC through 6.81kΩ 0.
Input Fine Gain +48V Spectrum Detail High Freq EQ HF EQ Peak LED Unbalance RF Filter Relay +65dB Jensen® Output Transformer Ground +15dB Relay +20dB Relay M8 Mic Pre Module Rectifier Jensen® JT-16-A Rectifier Relay Relay Relay Coarse Gain Rotary Switch Phase Invert 20dB Pad Super Low Z VU Meter Gain Switching Relay Bank Output 1/7/98 786 Block Diagram diagram 786 Block 13
¨ A Harman International Company 8760 South Sandy Pkwy. Sandy, Utah 84070 Phone: (801) 568-7660 Fax: (801) 568-7662 IntÕl Fax: (603) 672-4246 Questions or comments? E¥mail us at: customer@dbxpro.com or visit our World Wide Web home page at: www.dbxpro.
