Vectronics VEC-1680K - Manual

VEC-1680K Owner’s Manual Vacuum Tube Preamp
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INTRODUCTION
General Information: If names like Eric Clapton, Jimi Hendrix, and B.B. King
have personal meaning for you, you're gonna love this kit! Today's solid-state
amps can't match the booming sound of the legendary tube-driven powerhouses
built by Fender and Marshall. The key to that magic lies with the electron tube--
or "valve"--which has much softer saturation characteristics than the sharply
clipped response of transistor amplifiers.
With the VEC-1680K in line, your guitar's magnetic pick-ups are terminated
with the true ultra-high impedance load they were designed to feed, which
unleashes your instrument's natural full-bodied frequency response. And, when
you crank up the gain, each note expands in richness with warm even-order
harmonics, unlike the more jolting odd-order harmonics generated by transistors.
Virtually every great tube guitar amp ever built used a 12AX7 in its preamplifier
stage. When you fire up your VEC-1680K, you'll understand why!
Circuitry: The VEC-1680K uses a 12AX7 twin-triode, which is really two
individual tubes packaged in one glass envelope. The first stage runs "wide
open", with no manual gain control or negative feedback circuitry to load it
down. A Gain (or drive) control then regulates how hard you push the preamp's
second stage. Drive it lightly, and you get bell-like clarity. Drive it harder, and
you'll introduce progressively more fullness and grit! Most of the preamp's
distortion and coloring occurs in the second stage. At the preamp's output, the
signal is attenuated back down to "guitar" level. The Output control provides
added variable attenuation to set the optimum drive level for your power amp. A
built-in relay connected to the audio jacks lets you bypass the preamp, or--with
the click of a foot switch bring it on-line.
TOOLS AND SUPPLIES
Construction Area: Kit construction requires a clean, smooth, and well-lighted
area where you can easily organize and handle small parts without losing them.
An inexpensive sheet of white poster board makes an excellent construction
surface, while providing protection for the underlying table or desk. Diffused
overhead lighting is a plus, and a supplemental high-intensity desk lamp is
especially helpful for close-up work. Safety is always important! Use a suitable
high-temperature stand for your soldering iron, and keep the work area free of
clutter.
Universal Kit-building Tools: No special tools are required to complete this kit
beyond common items normally used for bench construction. We recommend
the following:
! Soldering Iron (grounded-tip and temperature-controlled preferred)