Specifications

PHONO AMPLIFIER
The phono amplifier uses a high technology integrated
circuit operational amplifier. Its differential input stage
has been optimized for low noise and low distortion
performance. The feedback network provides precision
RIAA frequency compensation. The network uses 1 %
metal film resistors and 5% polypropylene film
capacitors. To achieve low-noise performance it is
essential that the feedback network have a very low
impedance. As a consequence, the preamplifier must
be capable of operating as a power amplifier to drive
this impedance. The actual power output capability of
this preamplifier stage is more than 100 milliwatts, a
great margin beyond that which is required.
Input sensitivity of the phono amplifier is 2.5 millivolts
and the gain is 40dB at 1000Hz. It has a very wide
dynamic range. The phono input circuit will accept 60
millivolts without overload.
VOLUME CONTROL
A superior surround sound system requires a super
precision volume control. Tracking accuracy must be
near perfect or the audio image will shift as the control
is moved. Mclntosh engineers have designed a micro
processor controlled volume system that retains the
familiar VOLUME CONTROL KNOB but provides "State
of the Art" performance. All SIX channels track within
one quarter of a dB throughout most of their range. 256
steps are provided for excellent resolution and each
channel has ± 12dB of trim. The control microprocessor
also drives a two digit display that indicates % of
volume and the amount of trim used for system
calibration. The gain of the volume control section is
20dB.
LOUDNESS AMPLIFIER
At the input to the high level or loudness amplifier,
the signal passes through the mono stereo switch, then
through the volume control, and into the loudness
amplifier. In the past, loudness controls have typically
used simple passive circuits connected to a tap on the
volume control. As a consequence, compensation
accuracy was dependent on many variables such as
volume control position and differences in input level.
The MX130 uses active loudness control circuitry. An
integrated circuit operational amplifier is used here. It
has two feedback loops. One feedback loop has flat
response. The other feedback loop has loudness
compensation. A potentiometer is placed between these
two feedback loops making is possible to select any
combination of the two from a flat response to full
loudness compensation. The gain of the loudness
amplifier is 0dB.
TONE CONTROL AMPLIFIER
The tone control amplifier uses high technology
integrated circuit operational amplifiers. Its output stage
has been optimized for the best transient performance
and minimum distortion. Another operational amplifier
is arranged in a circuit configuration that is the
equivalent of a series turned circuit. The series tuned
circuit is inserted via a control potentiometer into either
the input or feedback circuit of the operational amplifier,
thereby, providing a boost and cut capability of 12dB.
The overall gain of the stage is 0dB. When the
potentiometer is at its center detent position, the tone
control elements are removed from the signal path.
CONTROL LOGIC
All inputs, outputs, CD, Tuner, and Video selector
lines are controlled by logic circuits in the MX130. The
logic is changed by front panel switches or by two
microprocessor IR decoders, one for LISTEN (A) and one
for RECORD (B). These microprocessor IR decoders are
programmed with exclusive Mclntosh software. They
receive data from the front panel or external sensors
and provide the command signals for input switching
and volume control. A third microprocessor decodes
the CD1, CD2 and TUNER function commands.
SYSTEM EXPANSION
Audio buffers and data switches feed a 25 pin
subminiature "D" connector for system expansion
through CR10s.
VIDEO SWITCHING
All video signal switching is done by MOSFET
switches.
VIDEO BUFFER AMPLIFIERS
Video buffer amplifiers feed the video outputs to
assure perfect matching and no loss in picture quality.
The response of the video section is 1 Hz to 12MHz so
high resolution signals present no problem to the
MX130.
RF OUTPUT
TV channel 3 or 4 output is provided by an internal
modulator. This signal can be used to feed remote areas
over a 75 ohm coaxial cable.
MclNTOSH LABORATORY INC., 2 CHAMBERS STREET, BINGHAMTON, NEW YORK 13903
MX130 Product Preview/Page 10