D.W. Fearn VT-1 Provozní pokyny Strana 1

VT-1VT-2Vacuum Tube MicrophonePreamplifiersOperating InstructionsD.W. FEARN

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers11History of the VT-1 and VT-2Vacuum Tube Microphone PreamplifiersONE DAY IN 1991 I was going through

D.W. FEARNVT-1 & VT-2 Microphone Preamplifers12Over the years much has changed in the world of electronic components. Were the necessaryparts stil

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers13is gross distortion — the output becomes a square wave. Square waves are not found in soundsthat we

D.W. FEARNVT-1 & VT-2 Microphone Preamplifers14The VT-2 was developed in 1995 in answer to requests from a number of our customers fora two-channe

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers151.SPECIFICATIONS Input 150 ohmsInput LoadImpedance 1.5k ohmsMinimum InputLevel -65 dBm nominalMax

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers172.DESCRIPTIONThe Model VT-1 and VT-2 Vacuum Tube Microphone Preamplifiers are designed to providere

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers193.INSTALLATION The VT-2 is carefully packed for shipment and it should survive all but the most bru

D.W. FEARNVT-1 & VT-2 Microphone PreamplifersHow to Contact us:Telephone:610-793-2526Fax:610-793-1479Mail: P.O. Box 57, Pocopson, PA 19366 U.S.A.S

D.W. FEARNVT-1 & VT-2 Microphone Preamplifers20if necessary. (Call the factory for detailed instructions). The ground pin of the power cord isinte

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers21All connectors are wired according to AES standard: pin 1 is ground (shield), pin 2 is “high”or “+

D.W. FEARNVT-1 & VT-2 Microphone Preamplifers22

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers234.OPERATIONInputSince the input cable will be carrying very low level audio, it is important that a

D.W. FEARNVT-1 & VT-2 Microphone Preamplifers24The VT-2 can feed balanced or unbalanced inputs with no need for any modification in out-put wiring

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers25Input “-20” position.In the “-20” position, a pad is inserted between the input connector and the i

D.W. FEARNVT-1 & VT-2 Microphone Preamplifers26The phantom powering circuit used in the VT-2 is suitable for use with all Neumann micro-phones, AK

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers27cate 0 on the meter. This is the standard “0 VU” level for all professional audio recordingequipmen

D.W. FEARNVT-1 & VT-2 Microphone Preamplifers28The controls should be set as follows. The numbers refer to Figure 2 on page 21.• Power (8). . . .

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers294. The output of the VT-2 should be fed directly to the recorder through the shortestpractical leng

D.W. FEARNHAND-CRAFTEDPROFESSIONALRECORDINGEQUIPMENTwww.dwfearn.comP.O. Box 57Pocopson, PA 19366 U.S.A.Tel: 610-793-2526Fax: 610-793-1479Certificate o

D.W. FEARNVT-1 & VT-2 Microphone Preamplifers30

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers315.THEORY OF OPERATION Input sectionMicrophone level (150 ohm source impedance, balanced, -50 dBm no

D.W. FEARNVT-1 & VT-2 Microphone Preamplifers32Input transformerThe input transformer is custom-made for D.W. Fearn by Jensen Transformers, Inc. a

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers33Third Stage The arm of the Attenuation potentiometer feeds the grid of the third stage (a 6072A), w

D.W. FEARNVT-1 & VT-2 Microphone Preamplifers34Filament SupplyThe power transformer output is rectified by a bridge rectifier and filtered before

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers356.MAINTENANCE The VT-2 is built with only the highest quality parts and will prove to be extremely

D.W. FEARNVT-1 & VT-2 Microphone Preamplifers36and grade them according to noise, microphonic response, distortion, and other character-istics. A

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers37VU Meter CalibrationThe meter amplifier circuit is stable and re-adjustment of the meter calibratio

D.W. FEARNVT-1 & VT-2 Microphone Preamplifers38Warranty RepairIf the VT-2 should develop a problem during the five-year warranty period, call the

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers39LP- 1 Line Pad Accessory The LP-1 Line Pad is an accessory for the VT-1 and VT-2 Vacuum Tube Microp

4

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers5VT-1 / VT-2 Vacuum Tube Microphone PreamplifierFinal Test ReportModel _______________ Serial Number

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers7Table of ContentsFinal Test ReportCE Certification Data Warranty ...

D.W. FEARNVT-1 & VT-2 Microphone Preamplifers8D.W. Fearn shall not be liable for technical or editorial errors or omissions in thismanual, nor for

D.W. FEARN VT-1 &VT-2 Microphone Preamplifers9Limited 5-Year WarrantyDuring the warranty period, D.W. Fearn will, at no additional charge, repair