D.W. Fearn VT-I Operating Instructions Manual Download Page 3

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T a b l e o f C o n t e n t s

History of the VT-I/F .............................................................................. 7

Specifications.......................................................................................... 9

Description..............................................................................................11

Installation ..............................................................................................13

Operation ................................................................................................17

Theory.....................................................................................................21

Maintenance............................................................................................23

List of Illustrations

Rear Panel Controls and Connections ....................................................14

Front Panel Controls and Connections...................................................15

Block Diagram........................................................................................21

Summary of Contents for VT-I

Page 1: ...VT I F Vacuum Tube Instrument Interface D W FEARN Operating Instructions...

Page 2: ...t 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 World Wide Web http www...

Page 3: ...ry of the VT I F 7 Specifications 9 Description 11 Installation 13 Operation 17 Theory 21 Maintenance 23 List of Illustrations Rear Panel Controls and Connections 14 Front Panel Controls and Connectio...

Page 4: ...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 guide may be photocopied or repr...

Page 5: ...s 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 I F Vacuum tubes are excluded from the 5 year warranty bu...

Page 6: ...accommodate the full dynamic range of sources likely to be connected to the VT I F Secondly the design had to be quiet After that it was just a matter of designing it to have the type of performance...

Page 7: ...VT 1 VT 2 with a different input design The output is identical to the VT 1 VT 2 but operates at a lower level The power supply is virtually identical to that used in the VT 1 VT 2 The VT I F has been...

Page 8: ...ulation Distortion 0 01 SMPTE Noise minimum 90 dB below output 22 cps to 22 kc bandwidth Output Transformer Balanced matches 150 ohm input Output Level 30 dBm nominal Maximum Output Level 12 dBm Cross...

Page 9: ...VT I F Vacuum Tube Instrument Interface D W FEARN 10...

Page 10: ...instruments It is capable of quality reproduction of a wide range of instrument levels The unit does not have the limitations of passive transformer type DIs and has greater headroom and warmth when c...

Page 11: ...es on the bottom The VT I F runs cool cooler in fact than many solid state devices Rack mounting is possible if a shelf is provided If the unit must be mounted in a rack be certain that there is adequ...

Page 12: ...and is required by most electrical codes If ground loop hum is detected a careful check of the studio grounding scheme is needed The VT I F is less susceptible to grounding problems than many studio...

Page 13: ...should be no additional connectors patch jacks switches etc between the instrument and the VT I F inputs It is important to keep the input lines as short as possible Avoid locating the VT I F where it...

Page 14: ...level is a nominal 30 dBm This is some what higher in level than a typical microphone Grounding and Shields A full discussion of proper studio wiring schemes is beyond the scope of this manual but in...

Page 15: ...connectors to the unit internal ground In most situations the GND LIFT switch 3 will remain in the down pin 1 to internal ground position In some situations particularly when an external instrument am...

Page 16: ...d when the VT I F is connected to an instrument and guitar amp simultaneously In this case use the GND LIFT 3 switch to find the proper IMPORTANT When using the VT I F with the D W Fearn VT 1 or VT 2...

Page 17: ...d directly to the recorder through the shortest practical lengths of quality cables Avoid additional cables con nectors junction boxes punch blocks or patch jacks Use gold contact con nectors if possi...

Page 18: ...20...

Page 19: ...ected 6072 or selected 12AY7 The input impedance is very high 1 megohm for proper loading of the musical instrument The first stage is capacitively coupled to the grid of the output stage Figure 3 VT...

Page 20: ...ngthened and the light output is more compatible with other modern studio equipment The power transformer is custom made for the VT I F and has primary taps for 100 120 or 220 volt operation The VT I...

Page 21: ...W Fearn 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 or distortion or a reduct...

Page 22: ...ect your fingers during tube replacement The VT I F should be turned off before removing tubes Allow at least one minute for the filter capacitors to discharge before tube removal or insertion Tubes a...

Page 23: ...a qualified service technician with vacuum tube equipment repair experience you may return the VT I F to the factory for repair Call first however for shipping information WARRANTY REPAIR If the VT I...

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