21
taper produced by the typical Electronic Volume Con-
trol Circuit is unacceptable for use in the C2300, as it
does not match the classic McIntosh Volume Control
Audio Taper. The C2300 incorporates electronic cir-
cuitry together with sophisticated firmware to produce
electronically the classic McIntosh Volume Control
Audio Taper, while maintaining the channel balance
and freedom from control noise.
The Volume Control on the Front Panel of the
C2300 is actually a special digital optical encoder. As
the Volume Control is rotated, a beam of Infra Red
Light is picked up by two internal sensors as a series
of digital pulses. Refer to
the exploded view in figure
29. The number of and time
between pulses are counted
by a Microprocessor which
in turn controls the McIn-
tosh designed Precision
Electronic Attenuator that
provides 213 steps in 0.5dB
increments and maintains the channel balance to
0.1dB.
With most Preamplifiers the Volume Control is
placed ahead of the Amplifying Circuitry providing
large dynamic range and freedom from input overload
however, background noise level is higher at lower
settings of the volume control. By placing the Volume
Control after the Amplifying Circuitry there is lower
background noise however, a reduction in dynamic
range and input overload is the result. The only cor-
rect way to design a high performance Preamplifier is
with two volume controls. This provides the benefits
of wide dynamic range, freedom from Input overload
and a background noise level that actually goes down
as the volume control setting is reduced. The special
controlling circuitry for this dual volume control
design is known as the McIntosh “Dynamic Control
Multiplexer”.
Meter and Circuitry
McIntosh solved the problems with ordinary meters
in the C2300. By developing electronic circuits the
meters are made to respond to short intervals with an
accuracy of 95%! To permit the eye to see such high
speed motion, the electronic circuits that drive the
meter pointer are time stretched. Special logarithmic
circuitry allows the meter to indicate a 60dB plus
range, without resorting to a Meter Range Switch.
Power Supply Circuits
To compliment the design of the C2300 there are fully
regulated power supplies. The special “R” core trans-
former supplies the necessary voltage/current for the
low and high voltage regulated circuitry.
Technical Description
Figure 29
Infrared
LED
Optical Disc
Sensors
C2300 Block Diagram
