D.W. Fearn VT-15 Operations Instructions

VT-15Vacuum TubeRecording ChannelOperating InstructionsD.W. FEARN

D.W. FEARNVT-15 Recording Channel12

D.W. FEARN VT-15 Recording Channel13Mic Input 150 ohmsInput LoadImpedance 1.5k ohmsMinimum InputLevel -65 dBm nominalMaximum InputLevel @ 20 cps -3

D.W. FEARNVT-15 Recording Channel14Compression Range up to 30dBCompression method Pulse-width modulatorEqualizer:Low-frequency Boost 100 cps, shelving

D.W. FEARN VT-15 Recording Channel152.DESCRIPTIONThe D.W. Fearn VT-15 utilizes circuitry developed for the VT-1/VT-2 Vacuum TubeMicrophone Preamplifie

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D.W. FEARN VT-15 Recording Channel173.INSTALLATION The VT-15 is carefully packed for shipment and it should survive all but the most brutal han-dling.

D.W. FEARNVT-15 Recording Channel18the back panel for installations that use separate chassis grounding. If ground loop hum isdetected, a careful chec

D.W. FEARN VT-15 Recording Channel194.OPERATIONINITIAL SET-UP IS CRITICALfor getting the best performance from your VT-15!The VT-15 has tremendous ver

D.W. FEARNVT-15 Recording Channel20Control Set-upInput toggle switches:Mic/Line switch - as appropriate for the source0/-20 switch - 0150/Lo-Z switch

D.W. FEARN VT-15 Recording Channel216. Adjust the Eq controls for the desired sound. (Remember to use the Boost and Cut togeth-er to shape the sound.)

D.W. FEARNVT-15 Recording ChannelHow to Contact us:Telephone: 610-793-2526Fax: 610-793-1479Mail: P.O. Box 57, Pocopson, PA 19366 U.S.A.Shipping Addres

D.W. FEARNVT-15 Recording Channel22CONTROLS (see Figure 1.)The VT-15 front panel is divided into three main areas of controls. On the left is the Inpu

D.W. FEARN VT-15 Recording Channel23es the polarity of the output of the VT-15. A detailed discussion of the application of phasereversal of individua

D.W. FEARNVT-15 Recording Channel24add distortion to low frequency sounds. (This is true of all compressors.) A fast release timeadds density to the s

D.W. FEARN VT-15 Recording Channel25should result in “0 VU” on a properly aligned recorder. (This reference level can be changed;see the Maintenance S

D.W. FEARNVT-15 Recording Channel261. Use the best quality mic cable you can. We don’t believe you have to use esotericwire, but do use a good cable d

D.W. FEARN VT-15 Recording Channel275.THEORY OF OPERATION Preamp SectionInput sectionMicrophone level (150 ohm source impedance, balanced, -50 dBm nom

D.W. FEARNVT-15 Recording Channel28response, low phase shift, excellent square wave response, low distortion, and high noiseimmunity. The secondary of

D.W. FEARN VT-15 Recording Channel29VU Meter and Meter AmplifierA two-stage IC operational amplifier is used to isolate the VU meter from the VT-15 ou

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D.W. FEARN VT-15 Recording Channel316.MAINTENANCE The VT-15 is built with only the highest quality parts and will prove to be extremely reliable.Vacuu

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

D.W. FEARNVT-15 Recording Channel32Tubes also sometimes develop a microphonic response — they will respond to ambient noiseand vibration. This can be

D.W. FEARN VT-15 Recording Channel33TroubleshootingMost problems will be traced to defective vacuum tubes. However, if normal tests do not eas-ily rev

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D.W. FEARN VT-15 Recording Channel5VT-15 Vacuum Tube Recording ChannelFinal Test ReportSerial Number_______________ Mains Voltage 120/240 set to ____

D.W. FEARN VT-15 Recording Channel7Table of ContentsRoHS Compliance Data ...3Final Test

D.W. FEARNVT-15 Recording Channel8D.W. Fearn shall not be liable for technical or editorial errors or omissions in thismanual, nor for incidental or c

D.W. FEARN VT-15 Recording Channel9Limited 5-Year WarrantyDuring the warranty period, D.W. Fearn will, at no additional charge, repair or replacedefec

D.W. FEARN VT-15 Recording Channel11History of the VT-15 Vacuum Tube Recording ChannelWith the success of the VT-1/VT-2 Vacuum Tube Microphone Preampl