range of the signal-strength meter is well chosen as an aid in
antenna orientation for best reception of problem stations.
The amplifier section, too, exemplifies the extra care that
sets the receiver apart. Whether the option that enables
switching in three speaker pairs simultaneously requires
them or not, it has three distinct protection systems. The
most conventional is triggered by a heat sensor and shuts
down the output until the heat sink has cooled to within safe
operating limits. The Sentry Monitor circuit reacts to abnor-
mal current conditions by restricting the drive to the output
transistors. And the Power Guard circuit responds to over-
drive that normally would create hard clipping by shaving off
the potentially dangerous harmonics—"softening" the clip
ping, so to speak. None impinges on normal operation; all
minimize the effects—aural, thermal, or electrical—of abnor-
mal operation.
The Power Guard, for example, limits peaks so smoothly
that you are unlikely ever to hear this receiver overload, as
such. The top LEDs in the front-panel power display—the one
possible concession to fashion in the design—are Power
Guard pilots; below that, the display is calibrated from 100
watts down to 0.1 watt in 5 dB steps. As we've said before,
we're not convinced of the utility of such indicators, but the
calibration points do seem relatively well chosen.
Two unusual features of the front panel are the equalizer/
tone controls and the "loudness" knob. The latter might bet-
ter be marked "contour" since it does not adjust midband
level like most loudness controls, but simply adds boost in the
deep bass plus some in the upper treble to compensate for
low listening levels. Like other separate-knob schemes, this
frees the loudness compensation from the volume control
and makes it adjustable to the actual listening levels through
the system; unlike some, the appropriate setting must be de-
termined by ear alone—which is arguably the most reasonable
approach.
The equalizer's five bands have maximum ranges of ap-
proximately ± 13 dB and are marked for center frequencies
of 30, 150, 500, 1,500, and 10,000 Hz—making them, re-
spectively, controls for subbass, bass, midrange, treble, and
sparkle. The 30-Hz control is most effective as a rumble-fil-
ter/boom-boost control; the top one might be used as a hiss
filter, though its maximum cut setting dulls the upper treble a
good deal. As an ensemble, they offer genuinely useful flex-
ibility; all have detented center "flat" positions.
While the lab measurements give little clue to the "extras"
from which the receiver's special qualities derive, they docu-
ment its very solid performance. Mclntosh appears to be
thinking in terms of listening quality rather than specsman-
ship (an attitude we applaud), so distortion, for example, is
only vanishingly low—not infinitesimally low. The frequency
response has been intentionally cut off beyond the audio
band to help maintain clean sound by inhibiting inter-
modulation with infrasonic and ultrasonic "garbage" (a de-
sign criterion that applies to the tuner section as well as the
amplifier); though this, similarly, may dismay those who judge
an amplifier by its square waves, the results with music seem
all the better for it. Tuner data are likewise very good—even
superb—with no offsetting cause for complaint of any kind.
It is obvious, too, that Mclntosh has a clearly formed idea of
the sort of user it is designing for: someone who, while he is
uninterested in playing the "pro," cares very much about
quality and craftsmanship. The cosmetics, the "feel," and the
sound quality of the Mac 4100 are all superb; the controls are
minimal for the degree of useful flexibility they provide, with
little if any concession to users who simply like to putter. This
truly is a receiver for music lovers.
CIRCLE 136 ON PAGE 89
FEBRUARY 1979
35
NEW MEASUREMENT STANDARDS
In making comparisons between current reports and those published in
the past, readers are cautioned to pay particular attention to the reference
levels and similar test criteria cited S/N ratios tor electronics, in par-
ticular, are measured very differently now that we have adopted salient
features of the new IHF amplifier-measurement standard While we be-
lieve that the new technique (which also implies a saner approach to
loading of all inputs and outputs) will result in measurements that more
perfectly reflect audible, in use effects. they cannot be compared directly
to the numbers resulting from the former, more conventional lab meas-
urements
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