McIntosh MX 110

MULTIPLEX DECODER
The multiplex decoder uses a special McIntosh
developed detecting circuit. One of the advan¬
tages of this circuit is the elimination of the
critical adjustments necessary with commonly
used matrixing methods. This circuit detects the
L+R sidebands and automatically matrixes the
recovered information with the L+R main
carrier signal. This circuit then yields the left and
the right program with maximum separation.
A temperature stabilized 19KC amplifier
locks-in a highly stable push-pull synchronous
oscillator. Apart from other advantages, this
method provides greatest noise immunity. Bal¬
anced detectors cancel the 38KC component
in the output and insure low distortion.
A three-section sharp cut off filter rejects SCA
interference and reduces susceptibility to spuri¬
ous signals.
The MX 110 has an MPX stereo indicator
that lights when the dial pointer crosses a station
broadcasting MPX stereo. A unique circuit using
a transistor operates the MPX stereo indicator.
The transistor is controlled by a differential
detecting circuit that amplifies the 19KC pilot
signal. This circuit automatically discriminates
between the 19KC signal and noise.
AUDIO
The MX 110 audio amplifier consists of three
negative-feedback amplifying sections in dupli¬
cate for the left and right stereo channels and a
separate L+R monophonic amplifier. The first
section in each channel is a feedback preamplifier
used to amplify and compensate for the input
signals coming from phonograph pickups or tape
heads. Level set controls are connected into the
output circuit of this preamplifier section when
the INPUT SELECTOR is switched to PHONO
1 or PHONO 2. These controls may be used to
maintain uniform loudness between phono and
tuner inputs. Skillful layout, grounding, and
shielding for low-hum pickup, metal film resistors,
low-noise tubes and extreme care in manufactur¬
ing combine to reduce noise and hum in t
input amplifiers.
octave) rumble and high-frequency filters are
associated with this section.
The third amplifier section is a two stage
negative feedback amplifier. The variable bass
and treble controls are included in the feedback
loop to maintain the lowest possible distortion.
For example a wave meter analysis of the three
amplifier sections of the MX 110 shows less
than 1/10 of 1% distortion at 3 volts output.
The MODE SELECTOR, balance controls and
left and right outputs are associated with the
third amplifier section.
The L+R monophonic amplifying section is a
feedback summing amplifier. It supplies mono¬
phonic output as well as L+R output.
The second amplifier section in each channel is
a cathode follower. The sharp cut-off (18db per
POWER SUPPLY
The power supply of the MX 110 has received
very special design attention. Two separate
rectifier circuits are used.
A full-wave rectifier supplies D.C. to the
heaters of all audio stages.
A bridge rectifier supplies D.C. to the anodes
of the audio stages.
A half-voltage tap on the bridge rectifier
supplies D.C. to the tuner stages.
This elaborate power supply design insures the
lowest possible background hum level and also
the maximum stability. In addition to this care¬
ful work the power transformer uses special
magnetic shielding to minimize possible hum
pickup in the MX 110 as well as in any other
equipment used with it.
Hi
2