Crown Audio VT-15 manual E O Ry O F O P E R At I O N, Preamp Section

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5 .

T H E O RY O F O P E R AT I O N

Preamp Section

Input section

Microphone level (150 ohm source impedance, balanced, -50 dBm nominal) or line level (600-ohm source, +4dBm nominal) audio enters through the XLR-3 female INPUT connec- tor to the Input selector switch bank. In the 0 position, the input is connected directly to the input transformer. The load imposed on the microphone is 1500 ohms, but varies slight- ly with frequency but is never lower than 1100 ohms. In the -20 position, the input passes through a balanced 20 dB pad. This pad is designed to maintain approximately the same load on the microphone as the input transformer.

In the Line position, a balanced pad of approximately 50dB attenuation is inserted on the input. In the Line position, the 48V phantom power and Lo-Z switches are locked-out.

The Mic/Inst switch changes the input from the rear panel XLR Input connector to the one- quarter inch front panel Inst jack. The audio from the Inst jack is fed directly to the grid of the first amplifier stage, bypassing all the input switching. The load impedance on the Inst input is 1 megohm.

All switching is through sealed gold-contact instrumentation relays with bifurcated contacts.

Phantom powering

+51 from the phantom power supply is switched on and off by the front panel +48 switch. A resistor drops the voltage as required depending on the current being drawn by the con- denser microphone electronics. This makes the phantom power supply universal for most 12 and 48 volt condenser microphones. The phantom powering resistors are precision matched to 0.10% or better. They provide exactly equal voltage to pins 2 and 3 respectively of the input connector. The switching is through sealed gold-contact instrumentation relays with bifurcat- ed contacts. In the “Off” position, the phantom power resistors are completely disconnected from the Input connector. When the VT-15 is in the Line position, the 48V switch is locked out.

Phase reversal switch

In the Normal position, input/output phase (polarity) is maintained (which must be inverted due to the design of the circuit). The balanced output is polarity reversed in the Reverse posi- tion. Switching is accomplished with a sealed, gold-contact instrumentation relay with bifur- cated contacts.

Input transformer

The input transformer is custom-made for D.W. Fearn by Jensen Transformers, Inc. and rep- resents the state of the art in transformer design. This is the same transformer that we use on the D.W. Fearn VT-1/VT-2 microphone preamplifiers. It exhibits extremely flat frequency

VT-15 Recording Channel

D.W. FEARN

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Contents Fearn How to Contact us Certificate of RoHS Compliance FearnPage VT-15 Vacuum Tube Recording Channel Final Test Report List of Illustrations B l e o f C o n t e n t sCopyright 2007 D.W. Fearn & Associates Limited 5-Year Warranty History of the VT-15 Vacuum Tube Recording Channel Fearn E C I F I C AT I O N S E C I F I C AT I O N S C O N T ’ D S C R I P T I O N Fearn S TA L L AT I O N PowerGrounding and Shields Input and Output ConnectionsE R AT I O N VT-15 front panel controls and indicatorsControl Set-up Output Mic InputOntrols see Figure Compressor Controls Equalization Controls Initial Set-Up Benc h TestFearn Preamp Section E O RY O F O P E R AT I O NCompression Section VU Meter and Meter Amplifier Fearn I N T E N a N C E VU Meter Calibration Warranty Repair TroubleshootingFactory Check-Out

VT-15 specifications

The Crown Audio VT-15 is a robust loudspeaker system that has gained recognition for its advanced technologies and impressive audio performance, making it ideal for various applications, including live events, installations, and broadcast scenarios. Built with durability and sound quality in mind, the VT-15 serves both professionals and enthusiasts in the audio industry.

One of the standout features of the VT-15 is its high-efficiency design, which is achieved through advanced driver technology. The loudspeaker is equipped with a premium 15-inch woofer that delivers powerful low-end reproduction, ensuring a solid bass presence that enhances the overall listening experience. This, combined with a high-frequency compression driver that operates at 1 inch, ensures clear and articulate treble frequencies, resulting in a balanced sound profile suitable for different musical genres.

The VT-15 incorporates Crown’s patented Waveguide technology, designed to provide consistent and controlled sound dispersion. This feature allows the loudspeaker to effectively cover large areas without experiencing significant drop-off in audio fidelity, making it a great choice for medium to large venues. The controlled directivity also means that listeners in various positions within the space can enjoy a similar audio experience, enhancing the performance of any event.

Another defining characteristic of the VT-15 is its rugged construction. Built with a reinforced enclosure, it is designed to withstand the rigors of touring and heavy use in fixed installations. The cabinet is constructed from high-quality materials that minimize vibration and resonance, further contributing to the clarity of sound. Its lightweight design allows for easier transport and setup, making it a practical choice for audio professionals on the go.

In terms of connectivity and compatibility, the VT-15 features versatile input options, allowing it to integrate seamlessly with various audio systems. Whether used in conjunction with other Crown products or compatible equipment from different brands, the VT-15 ensures flexibility in configuration.

Overall, the Crown Audio VT-15 stands out as a high-performance loudspeaker that combines advanced technologies, durability, and sound fidelity. Its powerful drivers and innovative design make it a reliable choice for any professional audio application, providing users with the quality and performance they demand. Whether for live music, presentations, or installations, the VT-15 delivers exceptional audio experiences that elevate any event or setting.
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