DC1 AUTOMATIC PRE-PROCESSOR WITH ADAPTIVE PROPORTIONAL GAIN ALGORITHM* (Version 2.0 and higher) OPERATING INSTRUCTIONS LECTROSONICS, INC.
INTRODUCTION The DC1 is a sophisticated, microprocessor-based audio signal processor which will add the capability of automatic mixing to any standard mixing console. The DC1 provides the capability to automate up to 4 standard channels. Since more than one DC1 may be used together, any number of channels may be automated. The DC1 is intended for use in any system that already has a standard mixing console, but where automation on some channels is helpful.
THEORY OF OPERATION Please refer to the block diagram of the DC1 for the following discussion. The DC1 has two major subsystems; the analog signal processing and the digital control section. The audio signal processing includes an ultra-low noise microphone preamp, a high-quality Voltage Controlled Amplifier (VCA), and an output transformer to prevent ground loops and RF interference. In addition, speech filters and precision log amplifiers detect audio signals over a wide dynamic range.
THEORY OF OPERATION (cont’d) The DC1 audio signal path is designed to eliminate any signal degradation from the DC1 itself. State of the art microphone preamplifier and voltage controlled amplifier (VCA) ICs are used to process the audio signals. When the Bypass mode of operation is selected from the front panel, all VCAs are set to unity gain and microphone signal pass through unaffected. A hardware bypass capability is provided by relays which switch all three pins of the input and output XLR connectors.
INSTALLATION Installation of the DC1 is quite straightforward. To use one DC1 by itself, simply plug the microphone cables from up to four microphones into the XLR inputs of the DC1. Connect the XLR outputs of the DC1 to the XLR inputs of the mixing console. If more than one DC1 is to be used, all but one must be set to the slave mode. Slave mode strapping is accomplished by removing the top cover of the DC1 and moving the two jumpers in the upper right hand corner of the DC1 from the forward position (i.e.
FRONT PANEL DESCRIPTION HEADROOM LED METER - Indicates the instantaneous amount of headroom available in the channel. Internal signals are monitored in each channel, and the Headroom LED meter shows the number of dB before channel clipping occurs. Note that even with no signal, the "40dB" LED is lit, indicating at least 40dB of headroom. ATTENUATION LED METER - Indicates the instantaneous amount of attenuation for each channel.
REAR PANEL DESCRIPTION MICROPHONE INPUT - Accepts a balanced microphone signal. Fully balanced differential input, RF filtered, front panel selectable 48 volt phantom supply. XLR type connector, Pin 2 is "+", Pin 3 is " ", and Pin 1 is ground. MICROPHONE OUTPUT - Feeds the input of a standard mixing console. Transformer balanced, XLR type connector, Pin 2 is "+", Pin 3 is " ", and Pin 1 is ground. EXPANSION IN/OUT CONNECTORS - provide the capability for more than one DC1 to be used in an installation.
OPERATING INSTRUCTIONS Before describing the setup procedure for the system, each function available in the DC1 will be explained. AUTO SKEW DISPLAY This function displays the instantaneous mix of Pre and Post VCA signals for each channel. The longer the display bar for any given channel, the greater is the proportion of Pre-VCA signal to Post-VCA signal. Except in the Auto Gain Skew "Off" mode, the current active microphone will display the longest bar.
SETUP PROCEDURE 1) Initialize the memory settings to factory defaults (optional.) If you do NOT want to lose any previously saved settings, proceed directly to step 2) below. After the DC1 is installed as outlined in the Installation section above, adjustments may be made to optimize the performance. The DC1 is shipped from the factory with all parameters preset. These presets provide a reasonable starting point from which to further optimize the DC1.
7) Set the Level Match for each channel. Press the UP button to advance to the Level Match screen then press SELECT repeatedly to move the cursor to the Value field. Press the UP and DOWN buttons to set the Level Match to the desired value. (Note: If the AutoSet procedure has already been performed, the Level Match will already be set and will not require readjustment in most cases. Level Match may be "fine tuned" here if necessary.
AUTOSET DESCRIPTION The AUTOSET function of the DC1 is included to automatically optimize the performance of the DC1. AUTOSET allows any mix of microphones to be used with the DC1, while insuring that all microphones will have equal access to the system. AUTOSET accomplishes this optimization by "listening" to each system microphone in turn for a period of about 5 seconds.
AUTOSET PROCEDURE STEP BY STEP INSTRUCTIONS 1) If the DC1 is used with a sound system, turn the sound system on and set it for a normal listening level. 2) Activate the auto set up mode: Turn the power off; Hold the MODE switch in and turn power on; The screen will display the level in dB of all four channels (See Figure 18). 3) Enter the AUTOSET screen: Press the MODE switch to enter the AUTOSET screen. CH. 1 will be displayed in the upper left corner of the screen (See Figure 19).
DC1 Function Summary and Default Settings Range Feature/Function Input Type Channel Channel Channel Channel Factory Default Mem 1 Factory Default Mem 2 LOW LOW LOW LOW LOW LOW LOW LOW OFF OFF OFF OFF OFF OFF OFF OFF AUTO AUTO AUTO AUTO AUTO AUTO AUTO AUTO 0dB 0dB 0dB 0dB 0dB 0dB 0dB 0db 20dB 20dB 20dB 20dB 20dB 20dB 20dB 20dB MED MED HIGH/LOW 1 2 3 4 Phantom Power Channel 1 Channel 2 Channel 3 Channel 4 ON/OFF Channel Mode Channel 1 Channel 2 Channel 3 Channel 4 AUTO DIRECT Level Match
SPECIFICATIONS Mic Input: Impedance: 8.1k Ohms balanced Type: Electronically balanced and RF filtered Gain: Unity EIN, 20-20kHz -127dBu at High Gain, -125dBu at Low Gain Maximum Input Level -20dBu for "High" Input Type, -40dBu for "Low" Input Type Mic Output: Impedance: Less than 15 Ohms Type: Transformer balanced Maximum Output Level: -20dBu at Low Gain, -40dBu at High Gain Phantom Power: +48 Volts System THD, 20-20kHz: Less than 0.1% System IMD, 60Hz/7kHz: Less than 0.
SERVICE AND REPAIR If your system malfunctions, you should attempt to correct or isolate the trouble before concluding that the equipment needs repair. Make sure you have followed the setup procedure and operating instructions. Check out the inter-connecting cords and then go through the TROUBLE SHOOTING section in the manual We strongly recommend that you do not try to repair the equipment yourself and do not have the local repair shop attempt anything other than the simplest repair.
LIMITED ONE YEAR WARRANTY The equipment is warranted for one year from date of purchase against defects in materials or workmanship provided it was purchased from an authorized dealer. This warranty does not cover equipment which has been abused or damaged by careless handling or shipping. This warranty does not apply to used or demonstrator equipment. Should any defect develop, we will, at our option, repair or replace any defective parts without charge for either parts or labor.
