Technical Description - McIntosh MC462 Owner's Manual

Technical Description

McIntosh Laboratory, the company who introduced
the world's first amplifier that could be called "High
Fidelity", has done it again. The McIntosh engineering
staff has created a Power Amplifier without compro-
mise, using the most advanced McIntosh circuit design
concepts.
14
The MC462 has a continuous average power output
rating of 450 watts and with a peak output current of
75 amperes per channel; making this one of the most
advanced amplifiers available today. The distortion
limits for the MC462 are no more than 0.005% at
rated power output for all frequencies from 20Hz to
Figure 13
20,000Hz. Typical performance
at mid frequencies is less than
0.002%. The true distortion
readings on the MC462 are so
low, it takes special measuring
techniques to make accurate
readings. The MC462 can deliver
the best possible performance
from any type of high quality
loudspeaker system. Refer to
figure 13.
Creating an amplifier with
this level of performance did not
come easily. Many months of de-
sign, testing and measuring were
required. Extensive controlled
listening tests, the ultimate form
of measuring, were made before
the final design was accepted.
Design Philosophy
The design philosophy incor-
porated in the MC462 involved
several different techniques, all
based on sound scientific logic.
Every stage of voltage or cur-
rent amplification must be as
linear as possible prior to the use
of negative feedback. McIntosh
engineers know how to properly
design negative feedback circuits so they contribute
to the extremely low distortion performance expected
from a McIntosh amplifier. The typical McIntosh
owner would never accept the approximately 100
times higher distortion of many non-feedback designs.
Double Balanced Push-Pull design is used from
input to output. Each half of the amplifier contains
complimentary balanced circuitry. The resulting Quad
Balanced configuration cancels even order distortion.
Refer to figure 14.
All transistors are selected to have nearly constant
current gain over the entire current range they must
cover. Output transistors in particular, have matched
uniform current gain, high current bandwidth prod-
uct and large active region safe operating area. These
Power Transistors are the very latest in semiconductor
technology and incorporate a new design known as
ThermalTrak™. Refer to figure 15. This allows for the
instantaneous and accurate monitoring of the Power
Transistor Temperature. The MC462
Power Output Circuitry has a specially
designed bias circuit to take full advan-
tage of the ThermalTrak™ Power Transis-
tors and thus precisely controls the power
amplifier operation over a wide range
of music conditions with the benefits of
lower distortion and cooler operation.
Precision metal film resistors and low
dielectric absorption film capacitors are
used in all critical circuit locations.
The output signals of the two balanced circuits
are coupled together in the unique McIntosh MC462
Output Autoformer. It provides low distortion power
transfer at frequencies from below 20Hz to well
beyond 20,000Hz with optimum impedance points of
two ohms, four ohms and eight ohms. The unequaled
Figure 15