D.W. Fearn VT-3 - Manual (Page 6)

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H i s t o r y o f t h e V T - 3 Va c u u m T u b e D I
As far back as I can remember, taking instruments “direct” has never sounded
very good to me. There always seemed to be a lack of dynamics, and a sterile qual-
ity to sounds recorded with a direct box (or DI).
The first tube DI that we produced was the VT-I/F Instrument Interface. It was
a beautiful piece, in a large, machined-aluminum case that you could drive a truck
over. Unfortunately, the cost of that case made it impossible to build the VT-I/F for
a reasonable price. Only about 75 were ever made, but the owners loved them, and
we kept getting requests for it. After several years of promises to bring out a rack-
mount version, we finally did so in 2006. The VT-3 is exactly the same as the VT-
I/F internally, except that we added a switchable high-pass filter and changed tubes
from the 6072A (which we use in all our preamps) to the 6N1P, an excellent-
sounding tube used in our VT-4 Eq and VT-7 Stereo Compressor.
Before beginning the design of the circuit, I spoke to engineers, producers, and
musicians about what they felt was lacking in DI boxes. Almost without exception,
they all said, “It’s got to have tons of headroom.” How much headroom was
enough? I spoke to a number of instrument pickup manufacturers and got an idea
of the peak output level of a variety of instruments. These figures were confirmed
with an oscilloscope placed directly across the output of various electric guitars,
basses, pianos, synthesizers, etc.
The first design goal was to accommodate the full dynamic range of sources
likely to be connected to the VT-3. Secondly, the design had to be quiet. After that,
it was just a matter of designing it to have the type of performance and packaging
that audio professionals have come to expect from our other products.
The decision was made early on that the output of the VT-3 would be at micro-
phone level. Although a line-level output is not difficult to design, it would
increase the cost. Besides, everyone has mic preamps available. Although the VT-
3 will work with virtually any mic preamp, it was designed to complement the VT-
1/VT-2 series of preamps.
We tried the first prototype on a solid-body electric guitar, and compared the
sound to several other respected DI boxes. We were astonished at first listen! It
sounded very close to the sound of the guitar through a good vacuum tube amp.