McIntosh MC602 User Manual

Page 14

Figure 15

Input Test Signal

balanced circuitry. The resulting double balanced configu-

ration cancels even order distortion. Refer to figure 12 on

page 13.

All transistors are selected to have nearly constant cur-

rent gain over the entire current range they must cover.

Output transistors in particular, have matched uniform cur-

rent gain, high current bandwidth product and large active

region safe operating area. An automatic tracking bias sys-

tem completely eliminates any trace of crossover distor-

tion. Precision metal film resistors and low dielectric ab-

sorption film capacitors are used in all critical circuit loca-

tions.

The output signals of the two balanced circuits are

coupled together in the unique McIntosh MC602 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 expertise of McIntosh in

the design and manufacturing of autoformers is legendary

in the high fidelity industry.

The high efficiency circuit design of the MC602 con-

tributes to low operating temperatures. More than 290

square inches of heat sink area keep the MC602 operating

safely with convection cooling. No fans are needed.

Autoformers

All solid state power amplifier output circuits work best

into what is called an optimum load. This optimum load

may vary considerably from what a loudspeaker requires.

In the case of more than one loudspeaker connected in par-

allel, the load to the power amplifier may drop to two ohms

or even less. A power amplifier connected to a load that is

lower than optimum, causes more output current to flow,

which results in extra heat being generated in the power

output stage. This increase in temperature will result in a

reduced life expectancy for the amplifier.

The Autoformer creates an ideal match between the

power amplifier output stage and the loudspeaker. A McIn-

tosh amplifier with an Autoformer can be used to safely

drive multiple speakers without reducing the life expect-

ancy of the

power ampli-

fier. Refer to

figure 13.

There is ab-

solutely no per-

formance limi-

tation with an

Autoformer. Its

frequency re-

Figure 13

sponse exceeds that of the output circuit itself, and extends

well beyond the audible range. Its distortion level is so low

it is virtually impossible to measure.

In the rare event of a power amplifier output circuit fail-

ure, the McIntosh Autoformer provides absolute protection

from possible damage to your valuable loudspeakers. The

unequaled expertise of McIntosh in the design and manu-

facturing of Autoformers is legendary in the high fidelity

industry. McIntosh engineers know how to do it right.

Protection Circuits

The MC602 incorporates its version of the McIntosh Sen-

try Monitor output transistor protection circuit. Refer to

Figure 14. There is absolutely no compromise in sonic per-

formance with this circuit, and it ensures safe operation of

the amplifier under even the most extreme operating condi-

tions. The different types of protection circuits incorpo-

rated in the MC602 insure a long and safe operating life.

This is just one of the many characteristics of McIntosh

Power Amplifiers that make them world famous.

The MC602 also includes the unique patented McIntosh

Power Guard circuit.

Power Guard eliminates

the possibility of ever

overdriving the amplifier

into clipping. Refer to

figures 15, 16 and 17. An

overdriven amplifier can

produce both audible and

inaudible distortion levels

exceeding 40%. The au-

dible distortion is un-

pleasant to hear, but the

inaudible ultrasonic dis-

tortion is also undesir-

Figure 14