D.W. Fearn VT-I/F - Manual (Page 19)

21
T H E O RY O F O P E R AT I O N
This circuit description refers to only one channel. Both channels are identical,
sharing only the power supply. (See Figure 3.)
Input section
The INSTRUMENT input jack is fed directly to the grid of the first amplifier
stage, a selected 6072 or selected 12AY7. The input impedance is very high (1
megohm) for proper loading of the musical instrument.
The first stage is capacitively-coupled to the grid of the output stage.
Figure 3. VT-I/F Block Diagram
Output Stage
The output tube is the second section of the 6072/12AY7. It is operated as a
cathode follower, capacitively-coupled to the custom output transformer. A resis-
From Instrument
To Guitar Amp
Mic Level Output
to Preamplifier