General Description; Technical Description - McIntosh C20 Owner's Manual

C20 STEREOPHONIC PREAMPLIFIER
The Mclntosh C20 Stereophonic Pre-amplifier is a
control center for any stereophonic sound system. This
control center is necessary to accurately perform four
specific functions to increase the enjoyment of stereo.
First, the control center amplifies weak electrical
impulses. As the record rotates on the turntable, un-
dulations in the grooves move the pick-up stylus ap-
proximately one-thousandth of an inch, in any direction,
from the rest position. From this slight mechanical
movement, the pick-up stylus generates a weak elec-
trical impulse on the order of a few thousandths of a
volt. To amplify and preserve the character of such an
electrical impulse, the finest amplifier performance is
required.
Second, every sound system is used in a different
acoustical environment. The tone balance of the music
You now own the finest expression of stereo crafts-
manship . . . designed and built to fulfill your needs.
Through direct consumer contact, a unique Mclntosh
marketing research program determines the application
of electronic and mechanical engineering to fit your
needs. Relentless research by Mclntosh engineers im-
proves the selection of materials and the circuits in
which they are used. It is this total concept of crafts-
manship directed to consumer satisfaction that has
maintained the Mclntosh reputation for excellence in
performance, quality, and reliability.
Perhaps you would like to know a few of the
features developed through research based on con-
sumer needs that place your C20 Pre-amplifier above
all other pre-amplifiers.
An example of the unique mechanical construction
throughout is emphasized on the back panel where low-
voltage program sources are connected to the C20. This
portion of the panel is cut out and mounted on small
electrical insulators. The ground circuit is connected
to the main chassis at only one point. By breaking the
path for circulating hum currents in this manner, the
hum and unwanted noises induced in other stereo
systems when used with various program sources and
combinations of program sources are eliminated.
Hum noises are also introduced into stereo sys-
tems by the magnetic fields produced by the power
transformer windings. The greatest care went into the
design and construction of the power transformer in
your C20. It is wound in such a way that the magnetic
fields produced by the windings tend to cancel. This is
accomplished by splitting the windings into two seg-
ments. Further reduction of the magnetic field intensity
is achieved through the use of additional magnetic and
electrical shielding. With these construction improve-

GENERAL DESCRIPTION

is affected by variations in environment. Also, people
listening to the music have varying ideas of correct
tone balance. To adequately compensate for these con-
ditions, a high-quality control center is needed.
monophonic records manufactured today, both domestic
and foreign. The control center must provide record
compensation for a great variety of recordings.
sources such as tuners, records, tape machines, micro-
phones, etc., a control center is needed to select and
switch these sources separately or in combination.
by the C20 and yet this instrument is easy to mount,
simple to operate, and is the finest in appearance.

TECHNICAL DESCRIPTION

ments the hum noises introduced by ordinary pre-
amplifiers are eliminated by the C20.
ponent parts in the C20 are mounted on military-type
terminal boards. This specialized construction prevents
damaging mechanical strains. In addition it makes
servicing, if ever required, much easier and more
effective.
separation of the left and right channels. The terminal
board at the rear of the C20 is associated with the right
channel and the terminal board at the front with the
left channel. C20 terminal boards are constructed of
natural bakelite because of its low-volume resistivity.
This prevents the gradual increase of electrical noise
common to other terminal board materials after con-
tinued use of the control center.
illuminated front panel to provide convenient reading
under low-level lighting conditions. This feature is of
particular importance when a closet is adapted to house
stereo equipment.
sive feature provided by the C20. With the start of
stereo FM broadcasting it will be important to tape
and preserve those special programs that will other-
wise never be heard again. This feature will be greatly
appreciated by you and your friends when recording
on portable tape machines.
with skilled engineering and manufacturing knowhow,
directed toward consumer needs, can produce such a
fine electronic instrument.
Third, there is a great variety of stereophonic and
Fourth, with programs originating from a variety of
All of these jobs are performed with excellence
Nearly all of the small resistor and capacitor com-
The mechanical layout of the C20 allows maximum
The C20 is the only control center that has an
Front panel tape input jacks are another exclu-
Only extensive research and planning combined
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