14
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.
The MC152 has a continuous average power output
rating of 150 watts per channel and with a peak output
current of 40 amperes; making this one of the most
advanced amplifiers available today. The distortion
limits for the MC152 are no more than 0.005% at
rated power output for all frequencies from 20Hz to
20,000Hz. Typical performance
at mid frequencies is less than
0.002%. The true distortion read-
ings on the MC152 are so low, it
takes special measuring tech-
niques to make accurate read-
ings. The MC152 can deliver the
best possible performance from
any type of high quality loud-
speaker 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 MC152 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 nega-
tive feedback. Refer to figure
14. 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.
The Balanced Push-Pull design is used from input
to output. Each channel of the amplifier contains com-
plimentary balanced circuitry. 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 product and large
active region safe operating area. These
Power Transistors are the very latest in
semiconductor technology and incorpo-
rate a new design known as Thermal-
Trak™. Refer to figure 16. This allows for
the instantaneous and accurate monitor-
ing of the Power Transistor Temperature.
The MC152 Power Output Circuitry has a
specially designed bias circuit to take full advantage
of the ThermalTrak™ Power Transistors 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 ca-
pacitors are used in all critical circuit locations.
Technical Description
Figure 16
Figure 14
Figure 13
