D.W.
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.
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 manual may be photocopied or reproduced in any form without prior written consent from D.W. Fearn. Copyright © 2000 D.W.
TABLE OF CONTENTS Warranty.................................................................................7 Specifications ........................................................................9 Features ...............................................................................11 History of the VT-4 ..............................................................13 Description ...........................................................................15 Installation ..................................
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 manufactured or supplied by D.W. Fearn; or by unauthorized modification of the VT-4. Vacuum tubes are excepted from the 5-year warranty, but are warranted for 90 days from date of purchase.
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 0 dB Frequency Response ± 0.5 dB 20 cps to 20 kc -3 dB @ 0.5 cps & 80 kc THD + Noise <0.10% 20 cps to 20 kc Intermodulation Distortion SMPTE: <0.
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 High Boost at 2, 3, 4, 5, 8, 10, 12, or 16 kHz, 0 to 14 dB in 2 dB steps High Bandwidth Q of 0.6, 0.8, 1.0, 1.4, or 1.7 High Frequency Cut at 1.
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.
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 characterisics of an individual track. A pair of VT-4s can be used to process a stereo mix with precise matching between units. It is designed for use in the professional recording environment.
3. I N S TA L L AT I O N 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 Mounting The VT-4 is designed for installation in a standard 19 inch rack. It requires 5.
Input and Output Connections Gold-plated XLR connectors are used for inputs and outputs. The input connector 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 “-.
4. O P E R AT I O N 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. This also applies to the High Boost and High Cut. The Mid-Cut control has a relatively low Q at minimal sttenuation settings. Thus, the band covered is quite broad.
5. T H E O RY O F O P E R AT I O N Input section Line level (600 ohm source impedance, balanced, +4 dBm nominal) audio enters through the XLR-3 female INPUT connector to the seven-position Input level control. The input is balanced-bridging, with an impedance of 40k ohms. The input transformer is made by Jensen Transformers Inc. The input switch is a passive pad on the primary of input transformer.
6. MAINTENANCE The VT-4 is built with only the highest quality parts and will prove to be extremely reli- able. 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. Phillips-head screws must be removed. When replacing the cover, position it so that the slotted ventillation holes are over the tubes (towards the back ). Vacuum Tubes Four 6N1P tubes are used in the VT-4.
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 clean- ing becomes necessary, we recommend using De-Oxit (Caig Laboratories). Follow the instructions provided with the product. If the switches are not used regularly, oxide and dirt can build up on the contacts.
