Crown Audio manual History of the VT-15 Vacuum Tube Recording Channel

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History of the VT-15 Vacuum Tube Recording Channel

With the success of the VT-1/VT-2 Vacuum Tube Microphone Preamplifiers, the VT- 4 LC Equalizer, the VT-7 Stereo Compressor, and the VT-I/F and VT-3 Vacuum Tube DIs, there was a great temptation to combine the features of all of these products into one record- ing channel.

But I had a problem with the concept. I did not want to be tied into having the com- pression come before the equalization, or vice-versa, so a prime design goal was to make the order of the processing switchable. That way the user has a choice of compression before equalization or equalization before compression. Different circumstances require different approaches to processing.

Achieving this switching with a minimum of noise and level change was solved quick- ly, but all the switching in the audio path could result in a degradation of the noise perform- ance of the VT-15.

By definition, an “all-in-one” box has many compromises over using separate units. I was not satisfied with the VT-15 until the overall performance was as close as possible to using a VT-1/VT-7/VT-4. The final result is a box that has about 4dB more noise than the separate units under most circumstances -- a negligible difference for most applications.

Because the VT-15 is capable of a tremendous amount of gain (about 90dB in the first prototype), it became a bit tricky to use properly. As long as you were familiar with optimiz- ing gain structure in a studio environment, it worked great. But not everyone has that back- ground, and in the heat of a session, it may get neglected. The result could be distortion -- and not the kind you would normally find pleasing. Optimizing the gain structure and head- room was an ongoing project, complicated by a period of 18 months when we could not keep up with the orders for our VT-7 Stereo Compressor. In fact, I put the VT-15 project on hold entirely for six months. When I returned to it over the summer of 2007, the pieces fell into place and the VT-15 was ready to meet the world.

The mic preamp is identical to the VT-1/VT-2 circuit with one exception: an instru- ment input has been added. The compressor is identical to one channel of the VT-7 Stereo Compressor. The equalization is a highly-simplified version of the VT-4 LC Equalizer, with just one frequency for the low-frequency boost, low-frequency cut, high-frequency boost, and the high-frequency cut. The chosen frequencies were based on my experience using the VT- 4 and feedback from many users.

Can the VT-15 replace the VT-1/VT-2, VT-7, and VT-4? Not really. The separate units have features that are just not practical to duplicate in the VT-15. But for many applications, the VT-15 provides the next best thing.

November 2007.

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 Troubleshooting Warranty RepairFactory 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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