® 376 Vacuum Tube Channel Strip w/Digital Out User Manual
IMPORTANT SAFETY INSTRUCTIONS WARNING FOR YOUR PROTECTION PLEASE READ THE FOLLOWING: CAUTION KEEP THESE INSTRUCTIONS 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 HEED ALL WARNINGS FOLLOW ALL INSTRUCTIONS SHOCK DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE CLEAN ONLY WITH A DAMP CLOTH.
IMPORTANT SAFETY INSTRUCTIONS LITHIUM BATTERY WARNING CAUTION! This product may contain a lithium battery.There is danger of explosion if the battery is incorrectly replaced. Replace only with an Eveready CR 2032 or equivalent. Make sure the battery is installed with the correct polarity. Discard used batteries according to manufacturer’s instructions. U.K. MAINS PLUG WARNING A molded mains plug that has been cut off from the cord is unsafe. Discard the mains plug at a suitable disposal facility.
376 Table of Contents Introduction Section 3 - Digital Applications 0.1 Defining the 376................................................i 3.1 Digital Output Front Panel Functions ...........12 0.2 Service Contact Info.........................................ii 3.2 Digital Rear Panel Connections .....................12 0.3 Warranty............................................................ii 3.3 Sync Input Sample Rate Selection.................13 0.4 Installation Recommendations...................
376 INTRODUCTION INTRO CUSTOMER SERVICE INFO 376 DEFINED WARRANTY INFO ®
376 Introduction INTRODUCTION Congratulations on your purchase of the dbx 376 Vacuum Tube Channel Strip with digital capabilities. For over 25 years, dbx has been the industry leader in dynamics processing. With the introduction of the 376, the standard for channel strip processors has now been completely redefined. Conventional channel strip processors are often limited in their ability to color and control the tonal characteristics of a vocal or mic’d application.
376 Introduction 0.2 Service Contact Info If you require technical support, contact dbx Customer Service. Be prepared to accurately describe the problem. Know the serial number of your unit. This is printed on a sticker attached to the rear panel. If you have not already taken the time to fill out your warranty registration card and send it in, please do so now. Before you return a product to the factory for service, we recommend you refer to the manual.
376 Introduction 0.4 Installation Recommendations FOR RACK MOUNT USE ONLY - Install the 376 in your rack with the provided rack screws. When installed in a rack, the unit should be positioned with enough room (at least one 1U above the and 1U below the unit) to allow proper ventilation. The 376 should not be mounted above or below anything that generates excessive heat. Ambient temperatures should not exceed 1130F (450C) when equipment is in use.
376 Section 1 Getting Started Getting Started ®
Section 1 376 Getting Started 1.1 Rear Panel Connections Power Switch Turns the 376 on and off. IEC Power Cord Receptacle This is the power cord receptacle of the 376. An IEC cord is included with the shipped product. AES/EBU Digital Connector Th e 3 7 6 p r o v id e s A E S/E B U d ig ita l o u tp u t fo r m a ttin g th r o u g h th e X L R c o n n e c to r . B e s u r e to u s e s h o r t le n g th s o f 1 1 0 Ωd ig ita l c a b le s r a th e r th a n s ta n d a r d X L R to X L R c a b le s .
376 Getting Started Section 1 1.2 Front Panel Controls Instrument Input This unbalanced high-impedance input connection is used to insert an instrument signal directly into the preamp. Use the LINE switch to make instrument input or the rear panel line input active. Plugging into the instrument jack will override the rear panel 1/4” input jack (line input must be selected).
Section 1 376 Getting Started Low control This control varies the gain of the low frequency equalization; the gain range is -15 to +15 dB. This filter is a low shelving filter at 80 Hz. Mid control This control varies the gain of the mid frequency equalization; the gain range is -15 to + 15 dB. The mid frequency filter is a bandpass configuration with variable frequency. Frequency control This control selects the center frequency for the mid frequency filter. The frequency range is 100 Hz to 8 kHz.
376 Getting Started Section 1 Output Level This knob controls the overall level of the output signal, and ranges from -20 to +20dB. Meter Select Switch This switch allows you to select display metering of either the digital or analog output signal. The analog level is scaled in dBu, while the digital level is scaled in dBFS. LightPipe™ Meter This meter displays either the analog or digital output signal. 1.
Section 1 376 Getting Started ® 6
376 Section 2 ANALOG APPLICATIONS ANALOG APPLICATIONS ®
Section 2 376 Analog Applications 2.1 Basic Analog Connection of the 376 • Turn off all equipment before making any connections. • Install the 376 in your rack with the provided rack screws. It is essential that when the 376 is being mounted in a rack mounting enclosure, the unit should be positioned with enough room (at least 1U of space above the unit and 1U of space at the below the unit) to allow proper ventilation. The 376 should not be mounted above or below anything that generates excessive heat.
376 Analog Applications Section 2 3). Turn the 376’s DRIVE control to the minimum position. Turn the OUTPUT LEVEL control to the 12 o’clock position, and apply power to the 376. Make sure your console’s gain fader is at the nominal level and begin to slowly increase the gain of the 376 using the DRIVE control. You should increase the gain until the mixing/recording device is operating at nominal signal input level. 4).
Section 2 376 Analog Applications 3). Enable the record function of the specific track of the recorder and open the specific tape track return in the console which corresponds to the track to which the 376 is connected. As you increase the setting of the DRIVE control, you should begin to hear the input of the 376 running through the recorder and returning to your console as a tape return. 4). Use the Parametric EQ LOW, MID, MID-FREQUENCY and HIGH controls to achieve the desired EQ settings of the 376.
376 Section 3 DIGITAL APPLICATIONS DIGITAL APPLICATIONS ®
Section 3 376 Digital Applications 3.1 Digital Output Front Functions of the 376 Dither Switch This switch is used to select the dither type algorithms including: TPDF, SNR2 , or None. Dither is random noise that is added to the audio signal which effectively eliminates the harmonic distortion created by truncation. See the“Truncation” graph in section D.2 of the Appendix. The LED will be lit RED for the SNR2 or GREEN for the TPDF dither algorithm. When the LED is off, dithering is not in use.
376 Digital Applications Section 3 AES/EBU Digital Connector Th e 3 7 6 p r o v id e s A E S/E B U d ig ita l o u tp u t fo r m a ttin g th r o u g h th e X L R c o n n e c to r . B e s u r e to u s e s h o r t le n g th s o f 1 1 0 Ω d ig ita l c a b le s r a th e r th a n s ta n d a r d X L R to X L R c a b le s . Us in g th e c o r r e c t c a b le s w ill p r e v e n t d ig ita l d r o p o u ts a n d o th e r in te r c o n n e c tio n p r o b le m s .
Section 3 376 Digital Applications 3.4 Direct Connection to a DAW (CPU) S/PDIF Rear Panel Connections • • Connect the source to the desired 1/4” TRS or XLR input. Connect the AES/EBU or S/PDIF output of the 376 and run into the AES/EBU or S/PDIF input interface of the DAW (CPU). Front Panel Digital Output Features 1). 2). 3). 4). 5). 6). Use Use Use Use Use Use the the the the the the METER switch to select digital output metering. DITHER switch to select the desired dither algorithm.
376 Digital Applications Section 3 3.5 Direct Connection to a Digital Mixer S/PDIF or AES/EBU Rear Panel Connections • Connect the source to the desired 1/4” TRS or XLR input jack. • Connect the AES/EBU or S/PDIF output of the 376 and run into the AES/EBU or S/PDIF input of the digital mixer. Front Panel Digital Output Features 1). 2). 3). 4). 5). 6). Use Use Use Use Use Use the the the the the the METER switch to select digital output metering. DITHER switch to select the desired dither algorithm.
Section 3 376 Digital Applications 3.6 A/D Conversion S/PDIF or AES/EBU Rear Panel Connections • • Connect the source to the desired 1/4” TRS or XLR input. Connect the AES/EBU or S/PDIF output of the 376 and run into the AES/EBU or S/PDIF input interface of the DAW (CPU). Front Panel Digital Output Features 1). 2). 3). 4). 5). 6). Use Use Use Use Use Use the the the the the the METER switch to select digital output metering. DITHER switch to select the desired dither algorithm.
376 Digital Applications Section 3 3.7 Multi-Tracking to Digital -24 -24 SYNC -24 AES/EBU or S/PDIF Rear Panel Connections • • Connect the source to the desired 1/4” TRS or XLR input jack. Connect the AES/EBU or S/PDIF output of the 376 and run into the AES/EBU or S/PDIF input of the digital mixer. Front Panel Digital Output Features 1). 2). 3). 4). 5). 6). Use Use Use Use Use Use the the the the the the METER switch to select digital output metering.
Section 3 376 Digital Applications 3.8 Analog and Digital Output Application MONITOR SOURCE ANALOG OUTPUT S/PDIF or AES/EBU The 376 gives you the unique option of utilizing the analog and digital outputs simultaneously. This option is ideal for using the analog output section as a reference monitoring signal of the digital signal.
376 Appendix APPENDIX APPENDIX Sync Input Info Block Diagram dbx Type IV™ White Paper Noise-Shaping Algorithms Truncation Specifications ®
Appendix A 376 Appendix A- Sync Input Info INSTRUCTIONS FOR QUALIFIED SERVICE PERSONNEL: CAUTION: These servicing instructions are for use by qualified service personnel only. To reduce the risk of electric shock, do not perform any servicing other than that contained in the operating instructions unless you are qualified to do so. Refer all servicing to qualified service personnel. Disconnect mains power before servicing. The dbx 376 comes with the word input 75Ω terminated.
Front Panel Instrument Input Rear Panel Line Input Insert - + Output Level 3-Band EQ Microphone Input Digital Analog Slow Phase Invert dbx TYPE IV Conversion System Analog Outputs Compressor Overeasy“ 20dB Pad Bar graph Meter EQ Clip LED +48V Output Format Shape dbx Pulsar Chip Drive Word - Out Word - In De-Esser Low Cut De-Esser Gain Reduction LED 12AU7 Tube S/PDIF Output AES/EBU Output Appendix Word Length DSP Dither Sample Rate Threshold LED Gain Reduction Meter Lin
Appendix C 376 Appendix C- Type IV™ White Paper dbx Type IV™ Conversion System White Paper by Roger Johnson The dbx Type IV™ Conversion System is a proprietary analog-to-digital (A/D) conversion process that combines the best attributes of digital conversion and analog recording processes to preserve the essence of the analog signal when it is converted to a digital format.
376 Type IV™ White Paper Appendix C to-noise performance since the signal is now closer to the noise floor. Because users of digital equipment have to be extremely careful not to exceed 0 dB FS (full-scale), they must use peak-reading headroom meters. On the other hand, the forgiving nature of analog tape allows users of analog recording equipment the luxury of only needing to monitor the average level using VU meters, often having no peak indicators whatsoever.
Appendix C 376 Appendix Input Signal Level TYPE IV™ Over Region +12 +8 +4 0 dB FS 0 -4 dB -4 A/D Converter Linear Region Noise Floor Figure 2 - Input Signal Levels Mapped to Type IV Over Region Fig. 2 illustrates the mapping function in a different way. Input levels are shown on the left of the graph, while converted levels are shown on the right. Notice the mapping of large signal excursions to the 4 dB “Type IV™ Over Region.
376 Appendix Appendix C Amplitude Time Figure 3a - Signal Having Low and High Frequency Content Amplitude A/D Clip Level Time A/D Clip Level Figure 3b - Signal of Fig.
Appendix C 376 Appendix Amplitude High-Frequency Information Completely Lost High-Frequency Content A/D Clip Level Low-Frequency Content Time A/D Clip Level High-Frequency Information Completely Lost Figure 3c - Disproportionate Loss of High-Frequency Information Due to Clipping Amplitude 0 dB FS } -4 A/D Clip Level TYPE IV™ Over Region Time -4 } 0 dB FS TYPE IV™ Over Region A/D Clip Level Figure 3d - Type IV Mapping Preserves High-Frequency Information Now you’re probably wondering, “Wh
376 Appendix Appendix D D.1 Noise-Shaping Algorithms D.1 16-Bit TPDF dither. (a) Shape “off”, (b) with shape set to “S1”, (c) with shape set to “S2.” Parameters: Input -60dBFS, 1 kHz; FFT Length= 2048, Sample Rate= 48 Khz, Averages= 32; Graph Steps= 1024. D.2 Truncation D.2 (a) 24-Bit word, (b) 16-Bit truncated output, no dither. Parameters: Input -60dBFS, 1 kHz; FFT Length= 2048, Sample Rate= 48 Khz, Averages= 32; Graph Steps= 1024. .
Appendix D 376 Appendix D.
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