D.W. Fearn VT-1 Instrucciones de operaciones descargar pdf (Pagina 32)

D.W. FEARN

VT-1 & VT-2 Microphone Preamplifers

Input transformer

The input transformer is custom-made for D.W. Fearn by Jensen Transformers, Inc. and rep-

esents the state of the art in transformer design. It exhibits extremely flat frequency

esponse, low phase shift, excellent square wave response, low distortion, and high noise

immunity. The secondary of is connected directly to the grid of the first amplifier stage.

Figure 4. VT-1/VT-2 Block Diagram (one channel shown)

First st

age

The first stage is a selected 6072 configured as a Class A voltage amplifier with a gain of

appr

ximately 30. Negative feedback from the plate of the second stage reduces distortion,

lattens the frequency response, and makes the gain of the first two stages less dependent on

individual v

acuum tube characteristics.

Second st

age

The output of the first stage is coupled to the grid of the second stage through a polystyrene

capacitor. This stage operates as a Class A voltage amplifier with a gain of approximately 30.

The plate is coupled t

ough a polypropylene capacitor to the top of a conductive plastic

otary potentiometer (Attenuation).

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D.W. Fearn VT-1 Instrucciones de operaciones Pagina 32