McIntosh MR-66, MA-6 Owners manual

MULTIPLEX

GENERAL DESCRIPTION

Use the Mclntosh MA6 Multiplex Adapter to
hear FM stereo from the MR66 FM Tuner.
Careful, thorough engineering and superior de­signing eliminate the need for critical adjust­ment in the field.

In multiplex broadcasting, both left and
right channels of a stereo program are trans­mitted over one FM station. The simple broad­casting of left channel and right channel
needed one basic improvement. Those who did
not have multiplex equipment would only
receive half a program. A new broadcast tech­nique called matrixing was developed to over­come this problem. In the new technique the
left and right programs (L + R) are added elec-

tronically. The L + R signal is centered on a

portion of the station's assigned spectrum

called the main carrier. At the same time the

left and right programs are subtracted (L- R).

ADAPTER

MA6

The L— R signal is centered on another portion
of the station's assigned spectrum called the
sub-carrier. (The FCC also permits the sta­tions, if they choose, to use another part of the
assigned spectrum for non stereo music trans-

mission. This additional program is called SCA,
sub-carrier authorization. The multiplex unit

electronically protects your stereo listening by

preventing SCA from interfering.)

In a FM tuner receiving multiplex, the sig-

nals are again matrixed. The matrixing in the

tuner separates the two channels so that we

hear the broadcast as stereo. The process

written algebraically is: (L + R) + (L-R) = 2L;

(L + R) - (L-R) = 2R. In a FM tuner not
equipped with a multiplex decoder, the broad­cast is heard as L + R, a complete monophonic

program.

TECHNICAL DESCRIPTION

The MA6 Multiplex Adapter uses a special

Mclntosh developed detecting circuit. One of
the advantages of this circuit is the elimina­tion of the critical adjustments necessary with
commonly used matrixing methods.

A temperature stabilized 19KC amplifier

locks-in a highly stable push-pull synchronous
oscillator. Apart from other advantages this

SPECIFICATIONS

Weight: 1 Ib. 2 oz.
Shipping Weight: 1 Ib. 10 oz.
Dimensions: 21/8 inches wide; 3¾ inches high

83/16 inches long.

Hum Level: Better than 60db below 100%

stereo modulation.

Distortion: Less than 0.3% (Multiplex Unit

only).

Suppression of pilot (19KC) and Carrier

(38KC): Greater than 40db below 100%

modulation.

method provides greatest noise immunity.
Balanced detectors cancel 19KC and 38KC
components in the output and assure low noise
and distortion.

A three-section sharp cut-off filter rejects

SCA interference and reduces susceptibility

to spurious signals.

INSTALLATION

The MA6 can be conveniently mounted to a

shelf or cabinet. Four wood screws are sup-

plied with the MA6 to secure it.

END VIEW

Figure 1. MA6 Multiplex Adapter Connected to the

MA6 MULTIPLEX DECODER

MR66 Back Panel Showing Multiplex

Adapter End View.

CONNECTING

The MA6 multiplex adapter power cable is

the gray cable attached to the multiplex

adapter chassis. On the end of this cable is a

five-prong plug. Align the prongs of the plug

with the power receptacle marked FM MULTI-

PLEX POWER on the back panel of the MR66
stereo tuner and plug the connector in.

Three 24 inch gray cables are supplied with

the MA6. Use these cables to complete the

connection of the MA6 to the MR66 Stereo
Tuner.

Connect the cables as follows:

1) Connect a cable between the receptacle
marked INPUT on the MA6 chassis to the
receptacle marked FM MULTIPLEX OUT­PUT on the back panel of the MR66.

2) Connect a cable between the receptacle

marked OUTPUT 1 on the MA6 chassis to

the receptacle marked MULTIPLEX IN-

PUTS 1 on the back panel of the MR66.

END VIEW

3) Connect a cable between the receptacle
marked OUTPUT 2 on the MA6 chassis to

the receptacle marked MULTIPLEX INPUT

2 on the back panel of the MR66.

IMPORTANT

The numbers 1 and 2 on the back panel of

the MR66 designate the left and right chan-

nels, respectively.

ANTENNA CONSIDERATIONS

For the satisfactory operation of a multiplex

tuner, more signal is needed than for mono-

phonic reception. Monophonic installations

that were satisfactory on an indoor antenna

may require the use of an outdoor antenna for
equivalent results. Satisfactory stereo requires
about 10 times as much signal from the an­tenna.

2.5M-AA134-113

LABORATORY INC.

2 Chambers Street

BINGHAMTON, N. Y.