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DW FEARN VT-4 Operating Instructions Manual

Vacuum tube lc equalizer
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D.W. FEARN
VT-4 Vacuum Tube LC Equalizer
Operating Instructions

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Summary of Contents for DW FEARN VT-4

  • Page 1 D.W. FEARN VT-4 Vacuum Tube LC Equalizer Operating Instructions...
  • Page 2 How to Contact us: Telephone: 610-793-2526 Fax: 610-793-1479 Mail: P.O. Box 57, Pocopson, PA 19366 U.S.A. Shipping Address: 182 Bragg Hill Road West Chester, PA 19382 U.S.A. e-mail: dwfearn@dwfearn.com Web: www.dwfearn.com...
  • Page 3 D.W. Fearn shall not be liable for technical or editorial errors or omissions in this manual, nor for incidental or consequential damages resulting from the use of this material. This instruction manual contains information protected by copyright. No part of this manu- al may be photocopied or reproduced in any form without prior written consent from D.W.

  • Page 4: Limited 5-Year Warranty

    LIMITED 5-YEAR WARRANTY During the warranty period, D.W. Fearn will, at no additional charge, repair or replace defective parts with new parts. This warranty does not extend to any VT-4 that has been damaged or rendered defective as a result of accident, misuse, or abuse; by the use of parts not manu- factured or supplied by D.W.
  • Page 5 History of the VT-4 Throughout my career in recording, there have always been a few equalizers that stood out as being exceptional. Among my favorites are the 1970s-era Neve input-strip eqs, and the Trident CB9066 parametric. I began my equalizer development project by first building a series of test circuits, using all the various tone-modification techniques.

  • Page 6: Specifications

    SPECIFICATIONS (All measurements made with +4dBm in and out, Eq switched in but all controls set to flat.) Input 600 ohms Input Load Impedance 40k ohms Minimum Input Level -20 dBm nominal Maximum Input Level @ 20 cps +25 dB Gain -4 dB Frequency...
  • Page 7 EQ Features (All controls are independent and can be used in any combination) Low Cut at 30, 40, 100, or 400 Hz, 0 to -18 dB shelving in 2 dB steps Low Boost at 20, 40, 60, or 140 Hz, 0 to 12 dB shelving in 2 dB steps Mid Cut at 200, 300, 400, 500, 600, or 700 Hz, 0 to -16 dB in 2 dB steps...
  • Page 8 DESCRIPTION The Model VT-4 Vacuum Tube LC Equalizer is designed to provide recording professionals with a sonically superior outboard processing device. It is typically used in sound recording studios for modifying the frequency response character- isics of an individual track. A pair of VT-4s can be used to process a stereo mix with precise matching between units.

  • Page 9: Installation

    INSTALLATION The VT-4 is carefully packed for shipment and it should survive all but the most brutal handling. If there is any damage, keep the shipping material for use during any possible claim for damage with the shipper. Included in the box: 1) The VT-4 Equalizer 2) Line cord 3) This instruction manual...
  • Page 10 Input and Output Connections Gold-plated XLR connectors are used for inputs and outputs. The input con- nector is female and the output male. All connectors are wired according to AES standard: pin 1 is ground (shield), pin 2 is “high” or “+,” and pin 3 is “low” or “-.” A positive voltage on pin 2 of the input will result in a positive voltage on pin 2 of the output Grounding and Shields A full discussion of proper studio wiring schemes is beyond the scope of this...
  • Page 11 Input Since the input cable will be carrying very high-quality audio, it is important that a well-shielded cable is used. Output The output of the VT-4 is line level, transformer balanced. Note that vacuum tube equipment is more sensitive to load impedance than solid state units. The VT-4 design was optimized for feeding a balanced bridging input (20k ohms or greater).

  • Page 12: Operation

    OPERATION The use of most controls on the VT-4 Equalizer is self-explanatory. One feature to note is that controls may be used in any combination. For example, use of both the Low Cut and Low Boost controls at the same time can result in some extraordinary effects.

  • Page 13: Theory Of Operation

    THEORY OF OPERATION Input section Line level (600 ohm source impedance, balanced, +4 dBm nominal) audio enters through the XLR-3 female INPUT connector to the eight-position Input level control. The input is balanced-bridging, with an impedance of approxi- mately 40k ohms. The input transformer is made by Jensen Transformers Inc. The input switch is between the secondary of the input transformer and the grid of the first stage of the input amplifier.

  • Page 14: Maintenance

    MAINTENANCE The VT-4 is built with only the highest quality parts and will prove to be extremely reliable. Vacuum tubes and electrolytic capacitors, however, have a finite useful life and must be replaced eventually. Top Cover Removal Removing the top cover allows access to the vacuum tubes. 6-32 allen-head bolts must be removed.
  • Page 15 Rotary Switches The rotary switches in the VT-4 were chosen for their self-cleaning property. In a clean environment (non-smoking, with frequent room and equipment vacuum cleaning), and with regular use, the rotary switches should require little attention for years. But if cleaning becomes necessary, we recommend using De-Oxit (Caig Laboratories).

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