McIntosh MC252 User Manual

17
Technical Description
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 signal of the circuit is coupled together in
the unique McIntosh MC252 Output Autoformer. It pro-
vides low distortion power transfer at frequencies from be-
low 20Hz to well beyond 20,000Hz with optimum imped-
ance points of two ohms, four ohms and eight ohms. The
unequaled expertise of McIntosh in the design and manu-
facturing of autoformers is legendary in the high fidelity
industry.
The high efficiency circuit design of the MC252 con-
tributes to low operating temperatures. More than 621
square inches of heat sink area keep the MC252 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
Figure 14
Block Diagram of the Amplifiers
and
Meter Circuitry

McIntosh MC252 Specifications

General

Power Output per Channel	250 watts
Number of Channels	2
Total Harmonic Distortion	0.005%
Frequency Response	20Hz to 20kHz
Signal to Noise Ratio	112dB
Damping Factor	>40
Dimensions	17-1/2" (44.5cm) wide, 7-5/8" (19.4cm) high (including feet), 20" (50.8cm) deep (including front panel and cables)
Weight	75 lbs (34.1 kg) net, 93 lbs (42.2 kg) in shipping carton
Power Output per Channel @ 2, 4 or 8 Ohms	250 watts
S/N Ratio	112dB
Dynamic Headroom	1.8dB
Rated Power Band	20Hz to 20kHz
Input Impedance	10k ohms (balanced), 20k ohms (unbalanced)
Frequency Response (+0, -0.25dB)	20Hz to 20kHz
Input Sensitivity	2.5V
Output Impedance	2, 4, 8 Ohms