D.W. Fearn VT-1 Operations Instructions

VT-3Vacuum TubeInstrument InterfaceD.W. FEARNOperating Instructions

D.W. FEARNVT-I/F Vacuum Tube Instrument Interface11DescriptionThe D.W. Fearn model VT-3 Vacuum Tube DI is designed to provide recordingprofessionals w

13InstallationThe VT-3 is carefully packed for shipment and should survive all but the mostbrutal handling. If there is any damage, keep the shipping

VT-I/F Vacuum Tube Instrument InterfaceD.W. FEARN14are required. The ground pin of the power cord is internally connected to the chas-sis. This confi

D.W. FEARNVT-I/F Vacuum Tube Instrument Interface15connectors at all times. It is not good practice to use both the front and rear con-nectors at the

VT-I/F Vacuum Tube Instrument InterfaceD.W. FEARN16Grounding and ShieldsA full discussion of proper studio wiring schemes is beyond the scope of thism

17OPERATIONFRONT PANEL CONTROLS (see Figure 2)Power switch (11)Primary power is applied to the VT-3 circuits when the Power switch (11) is inthe up po

VT-I/F Vacuum Tube Instrument InterfaceD.W. FEARN18Fluorescent lights and SCR dimmers are terrible electrical noise generators.Turn off the fluorescen

D.W. FEARNVT-I/F Vacuum Tube Instrument Interface191. The VT-3 must be located near the instrument. Ten feet of cable between theinstrument and the VT

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21THEORY OF OPERATIONThis circuit description refers to only one channel. Both channels are identical,sharing only the power supply. (See Figure 3.)I

How to Contact us:Telephone: 610-793-2526Fax: 610-793-1479Mail: P.O. Box 57, Pocopson, PA 19366 U.S.A.Shipping Address:182 Bragg Hill RoadWest Chester

VT-I/F Vacuum Tube Instrument InterfaceD.W. FEARN22The GND LIFT switch disconnects pin 1 of the OUTPUT connector from theinternal ground when the swit

D.W. FEARNVT-I/F Vacuum Tube Instrument Interface23MAINTENANCEThe VT-3 is built with only the highest quality parts and will prove to beextremely reli

VT-I/F Vacuum Tube Instrument InterfaceD.W. FEARN24microphonic response above -55 dBm is excessive. Replacement is indicatedunless the VT-3 always ope

D.W. FEARNVT-I/F Vacuum Tube Instrument Interface25repair experience, you may return the VT-3 to the factory for repair. Call first,however, for shipp

Table of ContentsHistory of the VT-3 ... 7Specifications...

NoticeD.W. Fearn shall not be liable for technical or editorial errors or omissions in this manual, norfor incidental or consequential damages resulti

LIMITED 5-YEAR WARRANTYDuring the warranty period, D.W. Fearn will, at no additional charge, repair or replace defective partswith new parts.This warr

7History of the VT-3 Vacuum Tube DIAs far back as I can remember, taking instruments “direct” has never soundedvery good to me. There always seemed to

VT-I/F Vacuum Tube Instrument InterfaceD.W. FEARN8This prototype was evaluated by a number of studio friends, who made someuseful suggestions. These s

D.W. FEARNVT-I/F Vacuum Tube Instrument Interface9Specifications(with 200 mV input)Input 200 mV nominalunbalancedInput LoadImpedance 1 megohm minimu

VT-I/F Vacuum Tube Instrument InterfaceD.W. FEARN10