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D.W. Fearn VT-7 Operating Instructions Manual

Manual is about: Vacuum Tube Compression Amplifier

Summary of VT-7

  • Page 1

    Vt-7 vacuum tube compression amplifier operating instructions d.W. Fearn.

  • Page 2: How to Contact Us:

    D.W. Fearn vt-7 compression amplifier how 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 www.Dwfearn.Com.

  • Page 3

    Certificate of rohs compliance d.W. Fearn is committed to manufacturing products that are fully-compliant with the eu rohs directive. The following products are compliant: vt-1 vt-2 vt-3 vt-4 vt-7 vt-15 lp-1 pdb this declaration is based on our understanding of the current rohs directive and from in...

  • Page 4

    D.W. Fearn vt-7 compression amplifier 5 vt-7 vacuum tube compression amplifier final test report model _______________ serial number_______________mains voltage ______________ date ___________________ tested by ________ vu calibrated to _______________ dbm test equipment ____________________________...

  • Page 5

    D.W. Fearn vt-7 compression amplifier 7 t a b l e o f c o n t e n t s final test report ............................................................................3 warranty .........................................................................................7 history of the vt-7 .................

  • Page 6

    D.W. Fearn vt-7 compression amplifier 8 d.W. Fearn shall not be liable for technical or editorial errors or omissions in this manual, nor for incidental or consequential damages resulting from the use of this material. This instruction manual contains information protected by copyright. No part of t...

  • Page 7

    D.W. Fearn vt-7 compression amplifier 9 limited 5-year warranty during the warranty period, d.W. Fearn will, at no additional charge, repair or replace defective parts with new parts. This warranty does not extend to any vt-7 that has been damaged or rendered defective as a result of accident, misus...

  • Page 8

    D.W. Fearn vt-7 compression amplifier 11 history of the vt-7 compression amplifier compression (or limiting) is sometimes seen as a necessary evil in the recording process. Often it is used to compensate for less than optimum performance or recording technique. However, when used appropriately, ther...

  • Page 9

    D.W. Fearn vt-7 compression amplifier 12 a look inside the vt-7 reveals a very full box with several densely-packed circuit boards for the gain control driver circuitry, interspersed with eight vacuum tubes. Because of the very high frequencies involved in the control circuitry, there are many surfa...

  • Page 10

    D.W. Fearn vt-7 compression amplifier 13 1 . S p e c i f i c at i o n s input 600 ohm source (nominal) balanced or unbalanced input load impedance 32k ohms, transformer balanced bridging nominal input level +4 dbm maximum input level @ 20 cps +25 dbm gain unity to +15db frequency response ± 0.2 db 2...

  • Page 11

    D.W. Fearn vt-7 compression amplifier 15 2 . D e s c r i p t i o n the model vt-7 vacuum tube compression amplifier is designed to provide recording pro- fessionals with a sonically superior signal processing device. It is typically used in sound recording studios for processing individual tracks or...

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    D.W. Fearn vt-7 compression amplifier 16.

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    D.W. Fearn vt-7 compression amplifier 17 3 . I n s ta l l at i o n the vt-7 is carefully packed for shipment and it should survive all but the most brutal han- dling. If there is any damage, keep the shipping material for use during any possible claim for damage with the shipper. You might also want...

  • Page 14

    D.W. Fearn vt-7 compression amplifier 18 power the vt-7 is designed to operate from 100, 120, or 220-240 volt, 50/60 hz power. The unit will be shipped for the voltage specified in the order, but may be changed in the field if nec- essary. (see the maintenance section for detailed instructions on ch...

  • Page 15

    D.W. Fearn vt-7 compression amplifier 19 4 . O p e r at i o n input since the input cable will be carrying high quality audio, it is important that a well-shielded cable is used. You should strive to minimize the number connectors, patch jacks, switches, etc. Between the source and the vt-7 input. O...

  • Page 16

    D.W. Fearn vt-7 compression amplifier 20 controls (see figure 2.) threshold the threshold control adjusts the point where compression begins. With the con- trol all the way down, there is no compression and the vt-7 operates as a straight amplifier. As the control is turned clockwise, the amount of ...

  • Page 17

    D.W. Fearn vt-7 compression amplifier 21 you can run a stereo signal with the switch in the separate position for an effect. On a stereo pair such as a piano or other sub-mix stereo source, the image will tend to shift from left to right as the signal becomes louder in one channel compared to the ot...

  • Page 18

    D.W. Fearn vt-7 compression amplifier 22 for 100 volt operation, internal wiring changes must be made. Contact the factory if this becomes necessary. Units ordered for 100 volt operation will be wired for that voltage only. Fuse the center part of the voltage selector is a fuseholder. For 100 and 12...

  • Page 19

    D.W. Fearn vt-7 compression amplifier 23 semi-professional equipment frequently uses a reference level of -10 dbv (roughly 14 db lower than pro equipment). Although the vt-7 can feed the unbalanced, -10 dbv inputs of semi-pro gear with no difficulty, the vt-7 vu meter will have to be recalibrated in...

  • Page 20

    D.W. Fearn vt-7 compression amplifier 25 5 . T h e o ry o f o p e r at i o n input section line level (low source impedance, balanced, +4 dbm nominal) audio enters through the xlr- 3 female input connector to a bridging input transformer. The load imposed on the source is 32k ohms and is constant re...

  • Page 21

    D.W. Fearn vt-7 compression amplifier 26 second stage the output of the first stage is coupled to the grid of the second stage through a polypropy- lene capacitor. This stage operates as a class a voltage amplifier with a gain of approximate- ly 20. Output stage the output stage operates as a cathod...

  • Page 22

    D.W. Fearn vt-7 compression amplifier 27 6 . M a i n t e n a n c e the vt-7 is built with only the highest quality parts and will prove to be extremely reliable. Vacuum tubes and electrolytic capacitors, however, have a finite useful life and must be replaced eventually. Top/bottom cover removal rem...

  • Page 23

    D.W. Fearn vt-7 compression amplifier 28 although you could purchase a batch of 6072a tubes and select the quietest one(s), it may be cost effective to buy a low-noise tube from the us. Current prices are $76.00 for a select- ed low-noise 6072a, and $20.00 for a tested 6n1p. (see www.Dwfearn.Com for...

  • Page 24

    D.W. Fearn vt-7 compression amplifier 29 gain reduction meter calibration the adjustments for the vu meter “0” calibration in the “gr” position are located on the pwm board. Contact the factory for complete adjustment instructions. Note that the meter calibration can be off but the vt-7 will continu...