D.W. Fearn VT-4 Operating Instructions Manual Download | Manualshive

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Operating Instructions

D.W. FEARN

VT-4 Vacuum Tube LC Equalizer

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Summary of Contents for VT-4

Page 1: ...Operating Instructions D W FEARN VT 4 Vacuum Tube LC Equalizer ...

Page 2: ...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: ... 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 Fearn Associates ...

Page 4: ...D W Fearn VT 4 Vacuum Tube LC Equalizer 5 TABLE OF CONTENTS Warranty 7 Specifications 9 Features 11 History of the VT 4 13 Description 15 Installation 17 Operation 19 Theory 21 Maintenance 23 ...

Page 5: ...suse 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 Except as expressly set forth in this Warranty D W Fearn makes no other warranties express or implied including any implied warranty of merchantability and fitness for a particu...

Page 6: ...Output low Z transformer balanced Maximum Output Level 22 dBm unterminated Power Requirements 100 120 or 220 VAC 50 60Hz 25 W Dimensions 19 48 26cm W 5 25 13 34cm H 9 22 86cm D VT 2 13 22 9cm Weight 14 lbs 6 35 kg SPECIFICATIONS Note Throughout this manual frequency is specified in cps cycles per second or kc kilocycles per second These units of measurement correspond to Hz and kHz respec tively S...

Page 7: ... 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 7 4 10 or 28 kHz 0 to 14 dB shelving in 2 dB steps Gain adjustable from 9 to 9 dB referenced to 4 dBm in 3 dB steps Note Throughout this manual frequency is specified in cps cycles per second or kc kilocycles per second These units of measure...

Page 8: ...f recording it was important to preserve the same sonic charac teristics that distinquished the preamps I decided to try the Svetlana 6N1P dual triode and was pleas antly surprised to find that it is a wonderful sounding tube with many of the same sonic characteris tics as the 6072A used in my preamps The active tube circuitry fell into place with relatively little effort Now it was time to make t...

Page 9: ...formers inductors and many other com ponents are custom made for the VT 4 All power supplies are solid state and fully regulated All rotary controls use high quality silver contact switches for precise repeatability and matching between units Much of the circuitry for the VT 4 is based on the highly successful D W Fearn VT 1 and VT 2 Vacuum Tube Microphone Preamplifiers Since line level signals ar...

Page 10: ...Be sure the bottom vent slots are not blocked It is essen tial that air can flow into the bottom and out of the top of the VT 4 Equipment that runs cool can last for a very long time In tight equipment enclosures be sure there is adequate air flow Forced air cooling will benefit all your equipment The VT 4 can also be used without a rack placed on a table counter or even on the floor Optional rubb...

Page 11: ... put cable however although not recommended the shields can often be connected at both ends without a problem 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 desig...

Page 12: ...Cut control is useful for reducing noise The highest frequency setting 28 kHz is particulary useful for digital recording Attenuation in this range may help avoid effects common with anti aliasing filters in A D converters The Input control allows processing of a wide range of input levels Also extreme amounts of boost could overload the input of the device being feed by the VT 4 Reducing the Inpu...

Page 13: ...or the VT 4 by Jensen Transformers Inc All capcitors are polystyrene or polypropylene types The rotary switches are semi sealed silver con tact types selected for quiet operation and long life Output section The output amplifier is similar to the Input section using a two stage Class A 6N1P triode amplifier with a cathode follower output The output is tranformer balanced using a custom made Jensen...

Page 14: ... tubes towards the back Vacuum Tubes Four 6N1P tubes are used in the VT 4 V101 and V201 are the input stage and V102 and V202 are the output stages Tube life is difficult to predict but it will probably be measured in years Catastrophic tube failure is rare with this type of device but a gradual increase in noise microphonics distortion or a reduction in headroom should indicate the need for repla...

Page 15: ... 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 Rotate the switches through their range a few times on a weekly basis to keep them clean Warranty Repair If the VT 4 should develop a problem during the five year warranty period call the fac tory for return shipping inst...

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