Technical Description - McIntosh MC452 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 MC452 has a continuous average power out-
put rating of 450 watts per channel and with a peak
output current of 75 amperes; making this one of the
most advanced amplifiers available today. The distor-
tion limits for the MC452 are no more than 0.005%
at rated power output for all frequencies from 20Hz
Figure 12
to 20,000Hz. Typical perfor-
mance at mid frequencies is
less than 0.002%. The true dis-
tortion readings on the MC452
are so low, it takes special
measuring techniques to make
accurate readings. The MC452
can deliver the best possible
performance from any type
of high quality loudspeaker
system. Refer to figure 12.
Creating an amplifier with
this level of performance did
not come easily. Many months
of design, testing and measur-
ing 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 MC452 involved
several different techniques,
all based on sound scientific
logic. Every stage of voltage
or current amplification must
be as linear as possible prior
to the use of negative feedback. McIntosh engineers
know how to properly design negative feedback cir-
cuits 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 15.
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 semiconduc-
tor technology and incorporate a new design known
as ThermalTrak™. Refer to figure 13.
This allows for the instantaneous and
accurate monitoring of the Power Tran-
sistor Temperature. The MC452 Power
Output Circuitry has a specially designed
bias circuit to take full advantage of the
ThermalTrak™ Power Transistors and
thus precisely controls the power ampli-
fier 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 MC452
Output Autoformer. It provides low distortion power
Figure 13