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to the unbalanced Inputs of the C500 are first converted to a
balanced signal before they are amplified. In a similar man-
ner the balanced audio signals are converted to unbalanced
signals before they are available to the unbalanced outputs
jacks.
Moving Coil Preamplifier
One of the popular types of Phono Cartridges for Turn-
tables used today are “Moving Coil”. Due to their design,
the Moving Coil Cartridge’s output voltage is typically in
the range of 300 to 500 microvolts (millionth of a volt) and
thus requires additional amplification in order to match the
output voltage of a “Moving Magnet/Induced Moving Mag-
net” cartridge type with 2.5 to 10 millivolts (thousandths of
a volt). The lower the output voltage of the cartridge, the
greater the level of amplification required and thus the
greater potential for higher noise levels being generated by
the circuitry.
McIntosh has designed a
new Totally Shielded Moving
Coil Preamplifier Module us-
ing special ultra low noise
circuitry with out the need for
a step-up transformer. Refer
to figure 101. The C500
utilizies a double filtered
power supply design, just for
the Moving Coil Preamplifier
Module. It offers the ability to
change the input impedance
from 25 ohms to 1000 ohms in six steps to match a wide
variety of Moving Coil Cartridges.
Technical Description, con’t
Logic Controlled Circuitry
All Inputs, Outputs, Data Ports, Power Control Outputs
and Trigger Outputs are controlled by Logic Circuits in the
C500C. The microprocessor is the heart of the Logic Cir-
cuits and is controlled by McIntosh developed software. It
implements all commands received from the Front Panel
Controls or the supplied Remote Controls and indicates
them on the Alphanumeric Display. Refer to figure 102.
When McIntosh Source Components are connected to
C500C Data Ports, basic command functions from the
C500 Remote Control are passed on to those components,
thus allowing one Remote Control to operate an entire
McIntosh Audio System. The Logic Circuits also sense
whether the C500 Preamplifier or C500 Tube Preamplifier
is connected to the C500 Controller and adjusts the opera-
tional functions automatically.
Meter and Circuitry
The lack of accurate performance in ordinary meters has
presented difficult and complex problems. Ordinary meters
are incapable of indicating the short interval information in
a sound wave. Refer to figure 103. The mass of the meter
movement is
too great to
respond to the
nearly instan-
taneous
changes in
music program
material. That
short interval
information
can have a du-
ration less
than as one-
half of one
thousandth of
a second. Even
if the meter
were capable
of such high velocity movement, the human eye could not
perceive the displayed information. McIntosh solved both
Figure 102
Figure 100
Figure 103
Figure 101