McIntosh MA-6 Multiplex Adaptor Vacuum Tubes for MR66 FM Tuner RARE
This MA-6 is a rare vintage piece straight out of McIntosh's history books! It's a stereo multiplex adaptor and was supplied with the McIntosh MR-66 for it to operate in FM "stereo" mode. This multiplexer uses vacuum tubes to match that gorgeous analog warmth you get from your vintage tuner. They don't make anything like this anymore, so if you have an MR-66, this adaptor is priceless!
Multiplex Broadcasting
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 electronically. 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).
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 transmission. 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 signals 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.
CONDITION
SPENCERTIFIED- Fully certified by Spencer
Refurbished and SPENCERTIFIED
Every function has been confirmed 100% working. We have cleaned it inside and out and replaced any worn parts. A recap was performed if necessary. All pots, knobs, connectors and boards have been cleaned with CRC cleaner.
The unit is complete, without any repairs. There are no burned electronics inside. The appearance is very good, with the chrome having some minor pitting
Cosmetic Condition: Very Good.
Functional Condition: Works Like New.
📦 Professionally packed and shipped with care.
WHAT'S IN THE BOX?
- McIntosh MA-6 Multiplex Adaptor Vacuum Tubes for MR66 FM Tuner RARE
Other information about the McIntosh MA6
- Uses a special Mclntosh developed detecting circuit
- Temperature-stabilized 19KC amplifier locks in a highly stable push-pull synchronous oscillator
- Balanced detectors cancel 19KC and 38KC components in the output and ensure low noise and distortion
- Three-section sharp cut-off filter rejects SCA interference and reduces susceptibility to spurious signals.
- 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 - Serial number: 134S0
DIMENSIONS
- 8.2" x 2.13" x 3.75" (Length x Width x Height)
- Weight: 1.2 lbs
INPUTS
- Audio In x1 (side)
OUTPUTS
- Analog Audio L/R x1 (side)
MANUFACTURE DATE and PLACE
- MFD. 1960 - 1962
- Made in U.S.A.
