D.W. Fearn VT-2 - Manual (Page 13)

D.W. FEARN
VT-1 & VT-2 Microphone Preamplifers
13
is gross distortion — the output becomes a square wave. Square waves are not found in sounds
that we consider musical, so our ears’ response to them is negative.
When a tube circuit distorts, the primary distortion product is even order harmonics. It so
happens that musical instruments also produce primarily even harmonics. By definition,
that’s what makes them “musical.” So you could say that tube circuits can add a musical
component to recorded sound. Fortunately, you can take your choice — keep the level rea-
sonable and obtain good clean audio, or run the circuit into distortion and generate some
harmonics that weren’t there to begin with.
There may be other factors at work, too, that make vacuum tube amplifiers sound different,
even when operated in the low distortion part of their range. I have not proven any of these
esoteric theories to myself yet, but I think they have merit. Here’s one: perhaps the minimal
number of active devices in the signal path makes a difference. My preamp has only four
active devices, while even the simplest solid state op amp circuit may have dozens.
But back to the story ....
Finally the preamp was ready for some serious testing in the studio. A number of friends in
the music business, both musicians and studio owners, were intrigued with the possibilities
of this device, so it was easy to get volunteers to test, evaluate, and give me additional input
on the performance. This resulted in a few more changes that have been incorporated into
the final design.
The VT-1 represents, I believe, not only the best performance attainable with this type of
circuit, but it will meet or exceed the performance of today’s top-of-the-line solid state
designs, while still providing the clarity and musicality that characterizes vacuum tube
“sound.” Not only that, but it is built to last. Solid construction is used throughout, and only
the best parts are used, many of them Mil-spec.
I have found over the years that one insidious source of distortion in the recording studio
comes from connectors, switches, relay contacts, patch jacks, etc. Although these connec-
tions may be perfectly adequate when new, after a period of time the contacts oxidize and get
a little dirty. Individually they may not cause much of a problem, but put your audio through
a few of them and you will start to hear the degradation.
To avoid this, the VT-1 design eliminates as many of these trouble-prone connections as pos-
sible. In fact, the only non-soldered connections from input to output are the input select and
phase reverse switches and the tube sockets. The input and phase switches are rotary types
with ceramic insulation and massive silver contacts. The phase switch is in the output circuit,
at line level, rather than on the input at very low level. In addition, the switches are chemical-
ly treated. And should they ever need cleaning, it is very easy to do a thorough job.
SO DOES THE VT-1 DUPLICATE the sound of my old RCA tube preamps? No, not exactly.
Gone are the hum, hiss, crackles, and bangs. And although I don’t have the old preamps to
do an AB comparison of the sound, I am certain that the better modern passive components
give the VT-1 a superior sound. The VT-1 has been used for all types of recording — vocals,
announcers, acoustic instruments, electric instruments, classical — and it works well with
them all.